Transcript WCIT - Trainex

Using Contaminant Information in
Evaluating Water Contamination Threats
and Incidents
U.S. Environmental Protection Agency
1
Course Overview
• This course is divided into ten parts
– Part 1: Course Goals and Definitions
– Part 2: Contaminants of Concern and Overview of Toxicology,
(Primarily as related to Chemical Contaminants)
– Part 3: Characteristics and Properties of Chemicals as they
Relate to Water Systems Contamination
– Part 4: Properties and Characteristics: Pathogens
– Part 5: Properties and Characteristics: Radiochemical Agents
– Part 6: Gathering and Managing Contaminant Information
– Part 7: Data Use for Consequence Analysis
– Part 8: Example Contamination Scenario
– Part 9: Action Items and Learning Tools
– Part 10: Appendix (Example Scenarios for other Contaminants)
• Please click on the links above to go to that part of
the presentation
2
Part 1:
Course Goals and Definitions
Return to Course Overview Slide
3
Course Goal
• Integrate existing water security knowledge, information,
resources and tools into a training to provide for a more
effective and efficient response to contamination threats
and incidents
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4
Course Goal
• Gain a basic understanding
of the following:
– Basic toxicology
– Contaminants of concern
– Types of contaminant
properties / characteristics
• Understand the process involved in researching and
analyzing contaminants of concern, including:
– Identifying appropriate sources of information
– Using data to assess potential threat and consequences to public
health
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5
Definitions
• Routine Threats and Incidents
– An actual occurrence in which hazards or threats result in a harmful,
dangerous, or otherwise unwanted outcome
•
•
•
•
Hoaxes
Security breaches
September 11, 2001
Anthrax-contaminated mail
• National Special Security Events (NSSE)
– A significant event or designated special event requiring security
• Presidential Inauguration
• State of the Union Address
• National conventions
• Olympics
• International summit conferences
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6
Part 2:
Contaminants of Concern and
Overview of Toxicology
(Primarily as Related to Chemical
Contaminants)
Return to Course Overview Slide
7
What are the Priority Drinking Water
Contaminants?
• More than 200 contaminants identified as posing a threat to
drinking water systems, based on:
– Health effects (toxicity or infectivity)
– Ability to be dispersed through distribution system
• Six main categories of contaminants
– Inorganic chemicals (e.g., cyanide)
– Organic chemicals (e.g., pesticides)
– Schedule 1 Chemical Warfare Agents (e.g., sulfur mustard)
– Biotoxins (e.g., ricin)
– Pathogens (e.g., Bacillus anthracis [Anthrax])
– Radiochemicals (e.g., Cesium-137)
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8
Toxicity Data
• What is it?
– A measure of the degree to which a substance can elicit a deleterious effect
(including death) in a given organism
• Why is it important?
– Toxicity is directly related to the public health outcome of a threat
– Many chemicals are more toxic via exposure routes other than ingestion
– The public can be exposed to drinking water contaminants via showering
(inhalation), bathing (dermal contact), as well as ingestion
– Different types (acute, chronic) depending on chemical, concentration, and
exposure route
Basic tenet of toxicology:
“Dosis facit venenum”
The dose makes the poison (Paracelus)
Return to Course Overview Slide
9
Basic Toxicology
• Acute, Sub-Acute
– Immediate or almost immediate adverse health effects from
exposure to a substance (for water contaminants, usually within a
day)
• Chronic, Sub-Chronic
– Adverse health effects resulting from long-term or repeated (chronic,
>10% of lifespan) exposure to a substance over a period of time
– Can occur at low levels that have no ACUTE effects
– Chronic health effects can be as severe as acute effects, but take
much longer to manifest
• Lethal, Sub-Lethal
– Causes death immediately or over a short period of time
– Sub-lethal is not quite lethal; less than lethal
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10
Exposure Routes
• Definition
– The route through which a chemical, physical, or biological agent may
enter the body
• Dermal Route
– Agent is absorbed directly through the skin
• Inhalation Route
– Agent enters through the respiratory tract or lungs
• Oral Ingestion Route
– Agent enters through the mouth and digestive system
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11
Exposure Routes (cont.)
• Other Routes
– Ocular (through the eyes)
– Mucous membranes
– Direct entry into the bloodstream through cuts or open sores
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12
Drinking Water and Exposure Routes
• Drinking water use provides opportunities for exposure
through all of these routes
• Drinking and Cooking
– Ingestion
– Dermal
• Bathing and Showering
– Inhalation
– Ocular
– Mucus membranes
–Direct entry through cuts or open sores
–Inadvertent ingestion
–Dermal
• Maintenance and Recreation
– Inhalation (Watering vegetable gardens)
– Dermal, Inadvertent ingestion (Swimming and wading pools)
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13
Toxicity Measures
• Some toxicity measurements are more applicable than
others in assessing the concentration at which a
contaminant will have acute or immediate impacts, while
others will have more chronic, long-term impacts
• Assessing acute or immediate impacts of contaminant:
– Lethal dose 50 (LD50), infectious dose 50 (ID50), or lethal
concentration 50 (LC50)
– No observed adverse effect level (NOAEL)
– Lowest observed adverse effect level (LOAEL)
• Assessing chronic, or long-term impacts of contaminant:
– Maximum contaminant level (MCL)
– Maximum contaminant level goal (MCLG)
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14
Toxicity Measures (cont.)
• Impacts will vary and may be based on acute or chronic
levels
– Health advisory (HA)
– Reference dose (RfD)
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15
MCLs and MCLGs
• Maximum Contaminant Level (MCL)
–
–
–
–
The highest level of a contaminant that is allowed in drinking water
Only established for regulated contaminants
Enforceable standards
Based on lifetime exposure risk (typically for an end point, such as
cancer)
• Maximum Contaminant Level Goals (MCLGs)
– Level of a contaminant in drinking water below which there is no
known or expected risk to health
– Allow for a margin of safety and are non-enforceable public health
goals
– The MCLG for some contaminants is zero, which means there is no
safe level for the contaminant
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16
Drinking Water Health Advisories (HAs)
• Estimate of acceptable drinking water levels for a
chemical substance based on health effects information
• HAs are not a legally enforceable Federal standard, but
serve as technical guidance to assist federal, state, and
local officials
• Developed for specific exposure durations
• Developed by EPA’s Office of Water to provide guidance
on non-regulated water contaminants and for
emergency contamination events
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17
Drinking Water Health Advisories (HAs) (cont.)
• 1-Day HA
– The concentration of a chemical in drinking water that is not
expected to cause any adverse noncarcinogenic effects for up to
1 day of exposure. The 1-day HA is normally designed to protect
a 10-kg child consuming 1 L of water per day
• 10-Day HA
– The concentration of a chemical in drinking water that is not
expected to cause any adverse noncarcinogenic effects for up to
10 days of exposure. The 10-day HA is also normally designed to
protect a 10-kg child consuming 1 L of water per day
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18
Drinking Water Health Advisories (HAs) (cont.)
• Lifetime HA
– The concentration of a chemical in drinking water that is not
expected to cause any adverse noncarcinogenic effects for a
lifetime of exposure
– Based on exposure of a 70-kg adult consuming 2L of water per
day
– The Lifetime HA for Group C carcinogens (i.e., possible human
carcinogen) includes an adjustment for possible carcinogenicity
• HAs are a concentration
– They can be compared to the concentration of what was found
in the contaminated water
• HAs function as benchmark
– If a contaminant is found in the water at a concentration higher
than the HA, then people might suffer adverse health effects
from drinking the contaminated water
Return to Course Overview Slide
19
Effect Levels
• No Observable Adverse Effect Level (NOAEL)
– Highest exposure level at which there are no biologically
significant increases in the frequency or severity of adverse effect
between the exposed population and its appropriate control
– Some effects may be produced at this level, but they are not
considered adverse or precursors of adverse effects
– In short — concentrations below the NOAEL are generally
considered safe, even when exposure is chronic
• Lowest Observable Adverse Effect Level (LOAEL)
– Lowest exposure level at which there are biologically significant
increases in frequency or severity of adverse effects between the
exposed population and its appropriate control group
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20
Reference Dose (RfD)
• Estimate of a daily exposure to the human population that is
likely to be without an appreciable risk of deleterious effects
during a lifetime.
– Uncertainty may span an order of magnitude
– Generally expressed in units of milligrams per kilogram of body weight
per day (mg/kg/day)
• Useful as a reference point from which to gauge the potential
effects of the chemical at other doses.
• Doses less than the RfD are not likely to be associated with
adverse health risks
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21
Reference Dose (RfD) (cont.)
• As the frequency and/or magnitude of the exposures
exceeding the RfD increase, the probability of adverse
effects in a human population increases
• However, all doses below the RfD may not be “acceptable”
(or risk-free) and all doses in excess of the RfD may not be
“unacceptable” (or result in adverse effects)
Return to Course Overview Slide
22
LD50, LC50, and ID50
• Lethal dose 50 (LD50)
– Dose of a chemical required to kill 50% of the experimental subjects
(e.g., rats, mice, cockroaches)
– Standard measurement of acute toxicity for chemicals stated in
milligrams (mg) of contaminant per kilogram (kg) of body weight
– Applies to ingestion and dermal exposure routes
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23
LD50, LC50, and ID50 (cont.)
• Lethal concentration 50 (LC50)
– Two types, depending on situation:
• Human inhalation (also called LCt) measured in milligrams per
cubic meter of air in a given time period (t)
• Environmental exposure by aquatic organisms, measured in
mg/L of water
• Often human data are not available, and animal models are used
• Infectious dose 50 (ID50)
– Number of infectious pathogens required to produce infection or
disease in 50% of the experimental subjects
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24
LD50, LC50, and ID50 (cont.)
• The lower the dose or concentration, the more toxic or
infectious the contaminant
• A contaminant with an LD50 value of 10 mg/kg is 10 times
more toxic than one with an LD50 of 100 mg/kg
• One limitation of animal models in determining what LD50,
LC50, or ID50 of a human population may be that different
animal species may have significantly different susceptibilities
to certain contaminants than humans
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25
LD50, LC50, and ID50 (cont.)
• LD50, LC50, or ID50 are published for a variety of exposure
routes, and only values for the same route are
comparable
• It is important to remember that the public can be
exposed through all these routes (e.g. via showering
(inhalation), bathing (dermal contact), as well as
ingestion)
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26
Related Acute Toxicity Measures
• Other Lethal Doses (LDs)
– Amount at which the contaminant is an LD to X percent of the
population (e.g., LD10)
– Lethal DoseLO (LDLO): The lowest published lethal dose of a chemical
via a particular exposure route
• The dose may greatly exceed the true lethal dose because it is
often determined from a single individual and circumstance (e.g., an
individual commits suicide by ingesting an entire can of poison; the
LDLO is based on what they consumed, not the MINIMUM lethal
dose)
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27
Other Toxicity Measurements
• Cell Death 50 (CD50)
– The dose of a contaminant required to produce death in 50% of
cells in study
• Convulsive Dose 50 (CD50)
– Median convulsive dose
• Chronic Dose 50 (CD50)
– Chronic dose resulting in chronic effects within 50% of the test
population
• Minimal Risk Levels (MRLs)
– Estimate of the daily human exposure to a hazardous substance
that is likely to be without appreciable risk of adverse non-cancer
health effects over a specified duration of exposure
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28
Toxicity Calculations
• MCLs and MCLGs can be compared directly to drinking
water concentrations to determine if there will be NO
potential effect
– The reverse is not necessarily true
– Complex risk calculations are required to determine the extent
of any potential effect
• For other toxicity values, calculations must be
performed to determine if the concentration level in
water poses a threat
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29
Toxicity Calculations (cont.)
• Example: Comparison of an oral LD50 with the concentration of the
contaminant in water:
• C = concentration (activity for radionuclides) of contaminant in water
• V = average volume of water consumed by an individual
• W = average weight of individual consuming water
• D = individual’s contaminant dose
– The contaminant dose can be compared to the LD50
• If the calculated dose is higher than the LD50, health effects in the
population could be severe and widespread
• If the calculated does is lower than the LD50, comparisons to LOAEL
and NOAEL should be made to determine if some effects may still
occur; these risk calculations may be complex
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30
Toxicity Measurements
• Many assumptions about exposure are made when
performing these types of calculations that may limit their
usefulness
– Average volume consumed may not reflect volumes actually
consumed by an individual
– Average weights do not reflect actual individual weights in a
population; may be necessary to do calculations at multiple weights
– Even if concentrations are below LD50; some adverse effects may
occur
– Common practice is to assume the exposure is to a 70kg human
– May need to do perform calculations for sensitive populations (e.g.
daycare center, or retirement facility, or hospital)
Return to Course Overview Slide
31
Part 3:
Characteristics and Properties
of Chemicals as they Relate to
Water Systems Contamination
Return to Course Overview Slide
32
Chemical Contaminants Overview
• Many potential chemical contaminants are widely available
and vary greatly in their health effects (e.g., their acute
toxicity)
• Detecting some of these contaminants in water presents
special challenges; detection of others is routine
• Drinking water distribution systems may spread the
contaminant over vast distances, although changes to the
contaminated water may occur within the distribution system
• Various physical and chemical properties of the
contaminants affect their ability to efficiently contaminate and
persist in water systems
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33
Chemical Contaminants Overview (cont.)
• Generally grouped into the following categories:
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Inorganic chemicals (e.g., cyanide)
Organic chemicals (e.g., pesticides)
Schedule 1 Chemical Weapons (e.g., sulfur mustard)
Biotoxins (e.g., ricin)
Radiochemicals (e.g., Cesium-137)
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34
Chemical Contaminants Overview (cont.)
• Chemical Weapons (CW): defined in the Chemical Weapons
Convention (www.cwc.gov); includes toxic chemicals covered
by a listing known as Schedules, including their precursors
– Schedule 1 contains chemicals that have been developed, produced,
stockpiled, or used as CW or chemicals that are precursors (any chemical
reactant that takes part at any stage in the production of a toxic chemical
regardless of method); Schedule 1 chemicals have no large-scale industrial
purpose
– Schedule 2 contains chemicals that pose a significant risk to the objectives of
the CWC or are CW precursors, and have no legitimate industrial use
– Schedule 3 contains "dual-use" chemicals—chemicals that have been
developed, produced, stockpiled, or used as CW or are CW precursors, but
are produced in large quantities for legitimate (non-CW) uses
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35
Chemical Contaminants Overview (cont.)
– CW are popularly grouped into five categories:
• Nerve (e.g., VX, Sarin)
• Blister (e.g., distilled mustard, nitrogen mustard, sulfur mustard)
• Choking (e.g., chlorine)
• Blood (e.g., hydrogen cyanide)
• Vomiting (e.g., adamsite)
– Some generalities can be made:
• Many are not stable in water
• Many are difficult to obtain
• Many are gases
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36
Chemical Contaminants Overview (cont.)
– Several Schedule 3 chemicals are found in water as a result of
disinfection (e.g., chloropicrin, cyanogen chloride, etc.)
– Water may not be the best delivery mechanism for CWs
– Properties of CWs are evaluated like other chemicals
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37
Chemical Contaminants Overview (cont.)
• Biotoxin: A toxin naturally produced by a microorganism,
plant, or animal
– Examples:
• Ricin – toxin that is derived from castor plant beans, Ricinus
communis
• Microcystins – toxins produced by blue-green algae
– Some have very low lethal dose relative to most contaminants;
however, some are less toxic than more common man-made organic
chemicals
– Although biotoxins may be used in an aerosol attack, they also
represent a concern for food and water contamination
– Properties evaluated like other chemicals
– Biotoxins are also organic chemicals
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38
Chemical Identity
• Chemicals can be uniquely identified by their Chemical
Abstract Registry Number, often called “CAS”
– In finding properties of chemicals, the CAS is often helpful because
many chemicals go by a lot of other names
• CAS numbers can be in chemical catalogs, databases, and
Material Safety Data Sheets (MSDS)
• Illustration: The CAS for glyphosate is 1071-83-6
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39
Chemical Detection
• The ability to detect a chemical contaminant in water is often
an important step in the investigation of contamination
• As used here, detection falls into two categories:
– Sensory Perception
– Chemical Analysis
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40
Chemical Detection (cont.)
• Sensory perception: usually occurs when the drinking
water customer complains that the water looks, smells,
and/or tastes unusual, but may or may not prevent the
customer from drinking the water
– Some contaminants may have distinctive odors or tastes,
although perception of these by customers can vary dramatically
– Is not always a sign of intentional contamination because some
water systems are prone to complaints, particularly at certain
times of year
– NEVER INTENTIONALLY SMELL or TASTE a suspected
sample
– Example: A customer complains of an almond smell to the water
• Hydrogen cyanide may smell like almonds
• On closer inspection, the odor is determined to be a new
almond scented shampoo
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41
Chemical Detection (cont.)
• Compliance monitoring for regulated chemical contaminants
will most likely not detect the presence of many of the potential
chemical agents; compliance monitoring for some chemicals is
sometimes only required a few times a year
• Water quality laboratories are often capable of analyzing water
for many regulated chemicals of concern. Special techniques
are required for confirming some Schedule 1 CW and
biotoxins.
• Early warning or rapid field detection is not available for many
contaminants of concern
• Changes in baseline water quality parameters (e.g., pH,
turbidity, residual chlorine) may or may not indicate the
presence of a chemical contaminant
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42
Fate and Transport of a Chemical within
a Drinking Water System
• The fate of a chemical as it moves through a water system
to the tap depends on the nature of the particular water
system and also on properties of the contaminant
• Predictions are often complicated and rely on:
- Accuracy of physical and chemical property data in the literature
- Knowledge of the individual drinking water system
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43
Drinking Water System
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44
Portion of Drinking Water Distribution System
• Understanding the behavior or water and
contaminants in a distribution system is a complex
task
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45
Contaminant Properties
• The next few slides will describe several contaminants
properties:
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–
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Solubility
Detectability (of the contaminant in water)
Treatability (at the water treatment plant)
Stability (of the contaminant in the distribution system)
• Along with a description of property, we’ll look at:
– How does the property help assess the threat
– What limitations about the property may be important
– Illustration about the property’s relevance to a water system
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46
Contaminant Property: Solubility
• What is solubility?
– The ability of a certain amount of chemical to dissolve in a certain
amount of a given solvent
– For example, one gram of sodium chloride dissolves in 2.8 mL of
water at room temperature
• How does this information help assess the threat?
– Solubility must be compared to the concentration of concern in water
(i.e., a highly toxic, less soluble chemical may be soluble enough to
pose a health threat); low solubility does not automatically imply
low threat
– Some chemicals, which are soluble in water, need to be dispersed
(e.g., by stirring) in order to dissolve
– Some insoluble chemicals can still be effectively dispersed in water,
although it presents a greater technical challenge (e.g., insoluble
metals may need to be dissolved in acid and then added to water)
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47
Contaminant Property: Solubility (cont.)
• What limitations in solubility information should you be
aware of?
– Solubility data are based on pure chemicals and sometimes solubility
is described using words such as “very”, “sparingly”, “slightly”, which
is not very helpful, especially for highly toxic chemicals
– Factors influenced by conditions in the distribution system affect
solubility (e.g., temperature, pH, TDS concentration)
– For contaminants added at high concentrations that exceed
solubility, a layer of contaminant may be found on top or at the
bottom of the water depending if the contaminant’s density (mass per
unit volume) is less or more than water (e.g., oil floats on water)
– The absence of a contaminant film on top (or bottom) of the water
does not necessarily mean that no contamination is present, but that
the contaminant is present but below its solubility limit
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48
Contaminant Property: Solubility (cont.)
• Illustration
– Someone adds a 10 kg (10,000,000 mg) of a contaminant to a
1,000,000 L water tank
• The LC50 of the liquid is 2000 mg/L to a water tank
• Solubility data indicates the solubility is 0.1 mg/L
• Where will the contaminant be (in the water or at the bottom of
the tank)?
– One source for solubility data says that a particular contaminant is
“practically insoluble”
• The LC50 of the contaminant is 30 mg/L
• How does the toxicity compare with the solubility?
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49
Contaminant Property: Treatability
• What is treatability?
– Ability of water treatment technologies (e.g., chlorination, sand
filtration, activated carbon, etc.) to remove a contaminant or
reduce its concentration in the water
• How does this information help assess the threat?
– The existing plant may be treating the water in such a way that
contamination is removed or mitigated rapidly, resulting in fewer
long term consequences
– Also relevant to remediation in the case of contamination
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50
Contaminant Property: Treatability (cont.)
• What limitations in this information should you be aware of?
– Efficacy of a particular process for a particular contaminant depends
on the treatment technologies conditions at the plant
– Treatment data may be unavailable for many contaminants
– Literature has inconsistent data for some contaminants-possibly due
to difference in treatment conditions
– Applies generally to contamination added to the system before the
treatment plant. However, water treatment plants add residual
disinfectant before the water leaves the plant and enters the
distribution system
• Illustration:
– Someone adds a quantity of a particular pesticide to the source water
of the treatment plant
– The treatment plant uses activated carbon, which the literature
indicates effectively removes the contaminant
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51
Contaminant Property: Stability
• What is stability?
– The ability of a contaminant to withstand degradation, which can
reduce the toxicity or infectivity of a contaminant
– With the distribution system, primarily a function of processes
such as hydrolysis, volatilization, reactivity, adsorption
– Biodegradation (degradation of the contaminant by
microorganisms) may be important in the source water
• How does this information help assess the threat?
– When available, degradation rate data may be used to estimate
the half-life of a contaminant in a water system; half-life is the
time is takes for half of the contaminant to degrade
– A chemical with a short half-life in a drinking water system may
not persist long enough to have significant effects on the public
– A chemical with a longer half-life in a drinking water system may
persist for sufficient time to have significant effects on the public
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52
Contaminant Properties: Stability (cont.)
• What limitations in this information should you be aware of?
– Stability data are based on pure chemicals, and depending on the
stability process, the data may not be available for the chemical
dissolved in water.
• For instance, reactivity data are sometimes given for the
undissolved compound, which can differ markedly from the
compounds behavior in water
– Estimates of half-life are not available for some contaminants
– Environmental fate and transport predictions rely on the accuracy of
physical and chemical property data in the literature
– Due to the complexity of drinking water distribution systems, the
amount of time that contaminated water can remain in the distribution
system varies tremendously by location, even within the same
distribution system; it can be an extremely complex task to apply
degradation rates when trying to estimate how much contaminant the
public has been exposed to
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53
Stability Related Process: Hydrolysis
• What is hydrolysis?
– A reaction that occurs between a chemical and the water itself, often
resulting in permanent degradation of the original chemical
• How does this information help assess the threat?
– Hydrolysis may produce byproducts that are less toxic than the parent
chemical, thus, hydrolysis sometimes, but not always, greatly reduces
the toxicity of contaminated water
– Contaminants, especially highly toxic ones, that are resistant to
hydrolysis may be of greater concern due to their persistence in water
• What limitations in this information should you be aware of?
– Hydrolysis rate is pH and temperature dependent
– Hydrolysis rate data are not available for all contaminants or are not
available for pH’s and temperatures of interest
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54
Stability Related Properties: Hydrolysis (cont.)
• Illustration
– The half-life of a certain pesticide is listed as 2 days
• This means that after two days, the concentration of the
contaminant will by 1/2, but will still be present
– The half-life of a particular chemical weapon is around 8 minutes at
room temperature
• Within an hour or two, the concentration is reduced to essentially
zero
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55
Stability Related Process: Volatilization
• What is volatilization from water?
– The process through which a contaminant dissolved in the water
enters the gas phase (i.e., the air above the water)
– Henry’s Law constants are essentially determined from the equilibrium
ratio of the concentration in the air to the concentration in the water
– Vapor density is the density of a gas relative to air
• How does this information help assess the threat?
– Henry’s Law constants provide an indication of whether the chemical
is likely to move from an aqueous phase into gas phase (e.g.,
contaminated water to the air)
– Vapor density provides an indication of how quickly a contaminant
could dissipate
– May help predict risk due to inhalation
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56
Stability Related Properties: Volatilization
(cont.)
• What limitations in this information should you be aware of?
– Henry’s Law Constant assume equilibrium conditions, but
volatilization is not an equilibrium process
– Applies to small concentrations
– Temperature dependent
– In water under specific conditions (e.g., pH), some contaminants
may co-exist in both volatile and non-volatile forms, which affects the
amount of volatile contaminant
• Illustration
– The dimensionless Henry’s Law constant for benzene is 0.25
• This means that concentration in the water is 4 times in the air.
– At drinking water pH’s, sodium cyanide is present as hydrogen
cyanide, which can volatilize from the water
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57
Stability Related Process: Reactivity
• What is reactivity?
– Reaction between a contaminant and another substance
– For water systems, a principal reaction of interest occurs between an
oxidant and the contaminant of concern
– One oxidant frequently found in finished drinking water is chlorine
• How does this information help assess the threat?
– The oxidation of a chemical contaminant frequently, but not always,
decreases the toxicity of the water
– Reaction rates for different contaminants can vary dramatically from
instantaneous to nearly imperceptible
• What limitations in this information should you be aware of?
– Oxidation is dependent on temperature and pH
– The presence and concentration of other substances in the water may
significantly affect the oxidation rate
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58
Stability Related Process: Reactivity
(cont.)
• Illustration
– A certain pesticide is known to react rapidly with chlorine
• You measure the chlorine residual at a tap and find there is a
large one
• It is less likely that the pesticide is present at that tap
– Contamination with a chlorine sensitive contaminant is
suspected, so you measure the chlorine residual at a tap
• You find very little
• Does this indicate contamination?
• Maybe not—some parts of the distribution system have far
less residual than was added at the plant due to natural
chlorine decay
– In arsenic treatment of water systems, oxidation changes the
chemical form of arsenic, and is known to frequently reduce
toxicity and ease of removal
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59
Stability Related Properties: Adsorption
•
What is adsorption?
– A measure of the tendency of a chemical to partition out of the water into a
substance with an organic-like phase (e.g., certain sediments, some water
system pipes and components, etc.)
– The octanol-water partition coefficient (KOW) may be an indicator. KOW is the
concentration of the contaminant in octanol divided by the concentration in
water after the contaminant equilibrates between the two solvents
•
How does this information help assess the threat?
– Related to the fate of a chemical in the water system
– May provide an indication of the chemical’s persistence in the water system
(e.g., need for remediation of the system)
– A compound with a higher KOW may be more likely to persistently contaminate
drinking water system components than a contaminant with a lower one. A
slow release of the contaminant from the water system components could taint
the water until enough water has passed through for sufficient desorption of
the contaminant.
60
Stability Related Properties: Adsorption
(cont.)
• What limitations in this information should you be aware of?
– The reliability of KOW as a predictor is highly dependent on both the chemical
and the material to which the chemical is partitioning. Not all materials have
an organic-like phase that behaves like octanol.
– This dependency may be unknown (e.g., given the wide variety of pipe
materials in use)
– Temperature-dependent
– Valid only under equilibrium conditions
• Illustration
– Hydrogen cyanide has a KOW of 0.5. An organic pesticide has a KOW of 1.3.
Which is more likely to persist in the pipes, leading to a slow release in the
water over time?
• Information gathered revealed that the pipes in that part of town were
made of a material to which neither contaminant measurably adsorbed.
61
Part 4:
Properties and Characteristics:
Pathogens
Return to Course Overview Slide
62
Pathogens Overview
• Disease-causing organisms that may result in illness or
death
• May be referred to as bioterrorism agents, replicating
agents, select agents, pathogens, microorganisms,
microbes
• Large quantities may be grown from small initial cultures
• Unique ability to multiply in the body over time and increase
their effect
• May be referred to by disease or by organism name:
– Salmonella typhi is the causative agent for typhoid fever
– Vibrio cholerae is the causative agent for cholera
– Yersinia pestis is the causative agent for plague
Return to Course Overview Slide
63
Pathogens Overview (cont.)
• Classified (for our purposes) into three categories
– Bacteria (including rickettsia and rickettsia-like organisms)
– Viruses
– Protozoa
Escherichia coli
bacteria
Return to Course Overview Slide
64
Bacteria
• Single-celled, prokaryotic (non-nucleated)
• Relatively easy to grow, may not require host cells for
growth; growth media often simple
• 0.1 - 10Fm in size
• Some are easily disinfected by chlorination, certain species
produce spores that are stable in some environmental
matrices for weeks or longer; also some may propagate in
a water system
Return to Course Overview Slide
65
Bacteria (cont.)
• Organisms may be susceptible to antibiotics
• Examples
–
–
–
–
Bacillus anthracis (anthrax)
Burkholderia pseudomallei (melioidosis)
Yersinia pestis (plague)
E. coli O157:H7 (hemorrhagic colitis)
Bacillus anthracis
Return to Course Overview Slide
66
Viruses
• Obligate intracellular parasites containing either DNA or
RNA with a protein coat. May also have a lipid envelope
• Unable to replicate or metabolize without a host cell
• Grown in cell cultures, embryonated eggs, or animals
• 0.01 - 0.1Fm in size
• Stability is estimated at less than a day to weeks for
some, unknown for others
• Antibiotics have no effect
• Examples:
– Variola (smallpox)
– Caliciviruses (e.g., Norwalkvirus)
– Hepatitis viruses (e.g., Hepatitis A)
Calicivirus
Return to Course Overview Slide
67
Protozoa
• Single-celled, eukaryotic (containing a nucleus), organisms;
0.8 - 70Fm in size
• Protozoa of concern are parasites. There are other nonprotozoan parasites, some of which may be of concern
• Some produce cysts (or oocysts) that are very stable
• May be susceptible to specialized antibiotics (e.g.,
Nitazoxanide)
• Examples:
– Cryptosporidium parvum (cryptosporidiosis)
– Toxoplasma gondii (toxoplasmosis)
– Entamoeba histolytica (amebic dysentery)
Return to Course Overview Slide
Cryptosporidium
68
Fate and Transport and Health Effects
•
Fate and Transport
– Many pathogens are stable in water long enough to pose a threat
– In suspension in water, rather than in solution
– Exposure routes may include: ingestion, inhalation, and/or dermal
contact
• Health Effects
– Small volumes of infectious material can potentially infect large
numbers of people
– May not cause immediate symptoms due to incubation period in host
– Symptoms may be vague/ambiguous (e.g., “flu-like symptoms”),
delaying diagnosis
Return to Course Overview Slide
69
Other Properties: Infectivity
• What is infectivity?
– A measure of the ability of a microorganism to establish itself in a
host species and begin to multiply
– May be expressed as an ID50 value (the number of organisms
needed to infect 50 percent of the exposed hosts in a given time
period)
• How does this information help assess the threat?
– Introduction of pathogen with a low ID50 value may be a significant
threat, even when low levels or concentrations are present
– Introduction of pathogen with very high ID50 value may require high
concentration of organisms to have the same impact
Return to Course Overview Slide
70
Other Properties: Infectivity (cont.)
• What are the limitations of infectious dose information?
– Knowledge of the source of the estimate is crucial to understanding
the significance of this number
• ID50 values may be derived from estimates made at outbreaks,
or from animal models (rather than human dosing studies).
• Variation in reported and actual ID50 may also arise from strain,
culture conditions, host factors, etc.
• ID50 values should include information on the route of infection.
ID50 values for ingestion and inhalation may differ by several
orders of magnitude
• Doses lower than the ID50 may cause illness, and this
relationship may not be linear
– Some studies report the “Minimum Infectious Dose”, which may
vary greatly from the ID50
– Many pathogen detection methods do not provide information on
infectivity
Return to Course Overview Slide
71
Other Properties: Incubation Period
• What is incubation period?
– The time between exposure and the appearance of symptoms
• How does this information help assess the threat?
– Pathogens with longer incubation times may no longer be viable or
present in the water system at or after the onset of symptoms
– If there is a continuous source of a pathogen, then a longer
incubation period may allow more individuals to be exposed
• What limitations in this information should you be aware of?
– Actual incubation period will depend on the following conditions:
• Initial dose
• Virulence of the organism (severity of disease produced)
• Rate of replication of the organism
• Health of the host (e.g., immunocompromised)
Return to Course Overview Slide
72
Other Properties: Virulence
• What is virulence?
– Virulence is a measure of the ability of an organism to cause
severe disease or death
– One measure of virulence is the mortality rate. This is generally
calculated as the number of deaths per thousand.
• How does this information help assess the threat?
– Diseases with higher mortality rates may be of greater
consequence to homeland security
• What limitations in this information should you be aware
of?
– Medical treatment may affect the mortality rate, so mortality may
be reported with both treated and untreated rates
– Mortality rates are dependant on correctly identifying underlying
cases, so the case definition used in generating the mortality rate
will be highly significant
Return to Course Overview Slide
73
Other Properties: Communicability
• What is communicability?
– Transmission of disease from person to person; the property of
being contagious
• How does this information help assess the threat?
– Even though “stop-use” notices to public may prevent new infections
for non-communicable diseases, new infections may continue to
occur for communicable pathogens via secondary transmission
• What limitations in this information should you be aware of?
– Degree of communicability may depend on the strain of organism
released
• Good sanitation practices can prevent the spread of many
communicable diseases
Return to Course Overview Slide
74
Other Properties: Stability
• What is stability?
– An assessment of the organism’s susceptibility to various
environmental factors while in the distribution system, including:
• Temperature, pH
• Osmotic pressure caused by differences in chemical
concentrations inside and outside the pathogen
• Residual chlorine
• How does this information help assess the threat?
– Stable organisms with environmentally resistant life stages (such as
anthrax spores and Cryptosporidium spp. oocysts) may survive
longer in the distribution system
– Some organisms may be more susceptible to residual chlorine
levels or osmotic pressure, reducing the possibility of transmission
Return to Course Overview Slide
75
Other Properties: Stability (cont.)
• What limitations in this information should you be aware
of?
– Data on organism stability may result from studies using different
organism strains or system conditions than are present any
specific distribution system
Salmonella typhi
Return to Course Overview Slide
76
Other Properties: Treatability
• What is treatability?
– Assessment of removal or inactivation of an organism by various
treatment processes
• How does this information help assess the threat?
– Determination of effectiveness of treatment at the water treatment
plant during event if organism is added to source water
– Determination of chlorine residual effectiveness in distribution
system during event if organism is added after treatment
– Evaluate the effectiveness of various options to decontaminate the
system
• What limitations in this information should you be aware of?
– Data on organism treatability may result from studies using different
strains or conditions
Return to Course Overview Slide
77
Challenges for Detection
• Most pathogens of concern will not be detected during
monitoring for routine contaminants or indicators (e.g., total
coliforms)
• Analytical results may not be indicative of virulence or
infectivity
• Water concentration techniques can be used prior to analysis
but overall analytical sensitivity may be below the
concentration of concern for some contaminants
• Most onsite drinking water utility laboratories are currently
capable of monitoring for indicator organisms, some of these
laboratories can conduct assays for some common
waterborne pathogens; however, capability and capacity for
many specific pathogens must be expanded
Return to Course Overview Slide
78
Challenges for Detection (cont.)
• The Select Agent Program (SAP) limits confirmatory
analysis for a list of “Select Agent” pathogens (e.g.,
Bacillus anthracis) to approved labs. Failure to comply
with the SAP can result in lengthy jail terms or heavy
fines.
• Many of the SAP approved labs conducting confirmatory
testing of Select Agent samples are part of Laboratory
Response Network (LRN)
Return to Course Overview Slide
79
Part 5:
Properties and Characteristics:
Radiochemical Agents
Return to Course Overview Slide
80
Radiochemical Agents Overview
• Two general types
– Naturally occurring (e.g., radium, uranium and thorium)
– Man-made; produced exclusively by nuclear reactors, accelerators,
cyclotrons, or nuclear weapons
• Neutron capture products in nuclear fuel rod assemblies, such as
plutonium-239 (239 Pu) and americium-241 (241Am)
• Fission products that accumulate in fuel rod assemblies or
produced by nuclear detonations, such as cesium-137 (137Cs), and
strontium-90 (90Sr) or corrosion/wear product activation such as
cobalt-60 (60Co)
• Accelerator produced medical radioisotopes, such as iodine-123
(123I) or cobalt-57 (57Co)
Return to Course Overview Slide
81
Radiochemical Agents Overview (cont.)
• Can be categorized by the type of radiation an unstable
isotope emits
– Alpha radiation: Particle emitted from the nucleus of an atom
consisting of two neutrons and two protons (same as a helium atom
nucleus)
– Beta radiation: Particle emitted from the nucleus of an atom
consisting of an electron or positron
– Gamma radiation: Emission from the nucleus of an atom consisting
of a high energy photon (gamma photon)
Return to Course Overview Slide
82
Radiochemical Agents Overview (cont.)
• Radiochemical agents may fall into one or multiple radiation
categories:
–
–
–
90Sr
is a beta emitter
137Cs and 60Co are both beta and gamma emitters
235U and 239Pu are both alpha and gamma emitters
• Sources of radiochemical agents:
–
–
–
–
–
–
Oil exploration equipment
Mining and milling sites for uranium, and rare earth ores
Power generation equipment
Weapons production, maintenance and disposal
Food and medical irradiators
Industrial radiography
Return to Course Overview Slide
83
Radiochemical Agents Overview (cont.)
• Small quantities widely used in many activities:
– Medical
– Food industry
– Laboratory/scientific research
Return to Course Overview Slide
84
Fate and Transport and Health Effects
• Fate and transport:
– Most will remain in solution
– Many are highly absorbable into biologic systems (e.g., 90Sr,
uranium, tritium)
– Concentrations will likely be uniform in the distribution system
• Health effects:
– If exposure is at low levels but for a long duration, or is at a
high, but non-fatal level for a short duration, the general longterm health effect is induction of cancers
– However, extremely high doses in short-term exposure events
cause cellular damage that may be significant enough to result
in death
Return to Course Overview Slide
85
Fate and Transport and Health Effects (cont.)
• Health effects, cont.:
– Many radioactive agents are organ-specific
• Iodine-129 [129I] uptake in the thyroid gland
• Uranium uptake and toxicity in kidneys
– For contaminated water, the
most significant health risk is
ingestion; water can
significantly attenuate (shield)
alpha and beta radiation (but
only minimally attenuate
gamma radiation), reducing
the threat of direct exposure
Return to Course Overview Slide
86
Other Properties: Toxicity
• What is toxicity?
– How poisonous or harmful a substance is in specified amounts
• How does this information help assess the threat?
– Some radioisotopes may result in both chemical- and radiation-induced
toxicity
– Chemical toxicity often is of greater concern (e.g., uranium)
– LD50 much higher than MCLs (for the regulated analytes)
– However, a single alpha particle may induce a mutational event
• What limitations in this information should you be aware of?
– Toxicity studies for radiochemical contaminants may not cover all
chemical species
– Most radiation exposure limits are based on dosimetric models
combined with radiation dose-response models, rather than empirical
studies
Return to Course Overview Slide
87
Other Properties: Speciation
• What is speciation?
– The types of chemical compounds in which a radioactive
contaminant may occur, such as a salt, oxide, hydroxide,
or organometallic complex, etc.
• How does this information help assess the threat?
– Can identify forms of radioactive species that may be in solution
– Different species will have different properties relevant to chemical
fate and transport and health effects
• What limitations in this information should you be aware of?
– Can be used only to estimate the actual threat of the contaminant of
concern
Return to Course Overview Slide
88
Other Properties: Solubility
• What is solubility?
– The amount of a solid that can be dissolved in a solvent (water)
• How does this information help assess the threat?
– Can be used to assess the exposure risk
– Radiochemical compounds with relatively high solubility may be more
of a threat (but low solubility does not equate to low threat)
– The species of the radioactive material of interest may be changed
from one with a low solubility (metal) to one with a high solubility
(metallic salt)
Return to Course Overview Slide
89
Other Properties: Solubility (cont.)
• What limitations in this information should you be aware of?
– Solubility of radiochemicals depends on pH and oxidizing potential
(Eh) of the water
– Solubility also influenced by the dominant anionic coordinating
species present in the water (e.g., sulfates, nitrates, carbonates,
chlorides)
– Many radiochemicals used in sealed sources for medical and
industry applications are in insoluble forms (e.g., impregnated
ceramics)
Return to Course Overview Slide
90
Other Properties: Reactivity
• What is reactivity?
– Ability of the radiochemical agent to undergo a chemical reaction with
other constituents in the matrix (e.g., finished drinking water)
• How does this information help assess the threat?
– Can affect solubility
– Important factor for fate and transport assessment and treatability
assessment
– Water drawn from the bottom of a storage tank may have higher
concentrations of the radioactive contaminant if mixing and turnover
only minimally affects the storage facilities in the distribution system
Return to Course Overview Slide
91
Other Properties: Reactivity (cont.)
• What limitations in this information should you be aware of?
– Reactivity may be influenced by pH, redox potential, residual
chlorine, and other chemical properties of water in the distribution
system
– Properties in distribution may not be the same as for the reference
reactivity of the radiochemical
Return to Course Overview Slide
92
Other Properties: Specific Activity
• What is specific activity?
– Measure of radioactivity per unit weight of the contaminant
• How does this information help assess the threat?
– Used to determine the radioactive intensity of the contaminant
– The more radioactive the contaminant (the higher specific activity),
and the greater the potential health effect
• What limitations in this information should you be aware of?
– Values usually provided for pure solids
– Information will need to be adjusted for dilution effects if in water
Return to Course Overview Slide
93
Other Properties: Half-Life
• What is half-life?
– The elapsed time required for one-half of the radioactive material
present to undergo radioactive decay
• How does this information help assess the threat?
– Can be used in calculating specific activities
– Specific activity used to assess the intensity of radioactivity present in
drinking water
– Also used to evaluate persistence in the environment
• What limitations in this information should you be aware of?
– No significant limitations – physical constants have been determined
experimentally
– Potency of daughter products must also be considered
Return to Course Overview Slide
94
Other Properties: Principal Daughter Products
• What are principal daughter products?
– The stable or radioactive isotopes formed when a specific radioisotope
(the “parent radioisotope”) decays
• How does this information help assess the threat?
– Can be used to identify other radioisotopes present from the decay of
the listed radioactive contaminant
– May have different stability/toxicity/solubility, etc., compared to parent;
must evaluate risk of daughters independently
• What limitations in this information should you be aware of?
– No significant limitations – Physical constants have been determined
experimentally
Return to Course Overview Slide
95
Challenges for Detection
• Radiochemical contaminants in water generally cannot be
identified by a change in most physical properties of the water
• Determining contaminant properties is useful primarily in
assessing radiation exposure risks after agent is identified –
not identifying the presence of the contaminant itself
• There are many advanced environmental radiochemistry
labs, however, capability and capacity at drinking water
utilities should be enhanced
Return to Course Overview Slide
96
Challenges for Detection (cont.)
• While it is possible to screen for specific types of radioactivity, no
method is available for field screening for all types radioactivity in
water
• Current GM probes can detect gamma activity in water; however,
alpha and beta radiations are shielded to a large extent by the
water and thus present a challenge in the area of rapid detection
• Geiger counter screening is limited for water screening
– Can identify only gross beta/gamma radioactivity
– Limited ability to screen for alpha emitters
• High-efficiency gamma detectors (scintillation detectors)
– Can identify fission products that are often beta/gamma emitters
– Cannot identify pure beta emitters, such as Sr-90, or I-129, or the
presence of alpha emitting contaminants, such as Pu-238/239
Return to Course Overview Slide
97
Part 6:
Gathering and Managing
Contaminant Information
Return to Course Overview Slide
98
Gathering the Data: Organizations
• Agency for Toxic Substances and Disease Registry (ATSDR)
– http://www.atsdr.cdc.gov/atsdrhome.html
– 1-888-422-8737
• Centers for Disease Control and Prevention (CDC)
– http://www.bt.cdc.gov/
– 1-888-246-2675
• Environmental Protection Agency (EPA)
– http://www.epa.gov
– Integrated Risk Information Hotline, 1-202-566-4676
– National Response Center, 1-800-424-8802
• National Institute for Occupational Safety and Health (NIOSH)
– http://www.cdc.gov/niosh/homepage.html
– 1-800-35-NIOSH
• Occupational Safety and Health Administration (OSHA)
– http://www.osha.gov/SLTC/emergencypreparedness/index.html
– 800-321-OSHA
Return to Course Overview Slide
99
Gathering the Data: Databases
• EPA’s Water Contaminant Information Tool
– Will contain peer reviewed information on contaminants that are of
concern to drinking water
– Will contain information on health effects, properties, fate and
transport, and drinking water treatment
– Currently exists as a prototype populated with 9 contaminants
– Currently being revised and further populated
– A partially populated version will be available on a secure Web site
by early 2005
Return to Course Overview Slide
100
Gathering the Data: Databases
• Hazardous Substances Databank (HSDB)
– A cluster of databases on toxicology, hazardous chemicals, and
related areas
– http://toxnet.nlm.nih.gov/
• Integrated Risk Information System (IRIS)
– A database of human health effects that may result from exposure to
various substances found in the environment
– http://www.epa.gov/iris/
– Integrated Risk Information Hotline: 202-566-4676
• NIOSH Emergency Response Cards
– http://www.cdc.gov/niosh/topics/emres/chemagent.html
• NIOSH Pocket Guide to Hazardous Substances
– http://www.cdc.gov/niosh/npg/npg.html
Return to Course Overview Slide
101
Gathering the Data: Databases (cont.)
• CHEMFATE
– A data value file containing 25 categories of environmental fate and
physical/chemical property information on commercially important
chemical compounds
– http://www.syrres.com/esc/chemfate.htm
• PHYSPROP
– Online interactive demo of physical property data about 25,000
compounds
– http://www.syrres.com/esc/physdemo.htm
• ATSDR HazDat Database
– Provides access to information on the release of hazardous
substances from Superfund sites or from emergency events and on
the effects of hazardous substances on the health of human
populations
– http://www.atsdr.cdc.gov/hazdat.html
Return to Course Overview Slide
102
Gathering the Data: Databases (cont.)
• Food and Drug Administration (FDA) Bad Bug Book
– Handbook providing basic facts regarding food-borne pathogenic
microorganisms and natural toxins; consolidates information from
FDA, CDC, USDA, and the National Institutes of Health
– http://vm.cfsan.fda.gov/~mow/intro.html
• United Kingdom Water Industry Research (UKWIR)
Contaminant Database
– Available through WaterISAC for a fee
– EPA Regions should have access to WaterISAC, and thus the
UKWIR database
– http://www.waterisac.org
Return to Course Overview Slide
103
Gathering the Data: Scientific Literature
• The following information sources have a fee associated
with them, but check within your local office, as you may
currently have access or have a subscription:
– Ovid Biomedical Journal Database
– FirstSearch (Worldcat)
– Science Citation Index (Web of Science)
– ProQuest
– Biological Abstracts
– STN Online (Chemical Abstracts and more than 140 other scientific
databases)
– DIALOG
– American Chemical Society journal publications online
Return to Course Overview Slide
104
Gathering the Data: Scientific Literature (cont.)
• The following sources are available on-line at no cost:
– American Society for Microbiology journal publications on line
• http://www.asm.org/
• Abstracts and full text articles are available at no cost from 1994
through November 2003
– National Institutes of Health, National Library of Medicine
• http://www.nlm.nih.gov/
• Abstracts and full text articles are available at no cost from 1992
Return to Course Overview Slide
105
Gathering the Data: Subject Matter Experts
• Government
– EPA Water Security Division
• Expertise on overall threat analysis, response, NSSEs,
contaminant evaluation
• 202-564-3779 (not for emergencies)
• During emergency situations call: 202-564-3850
– EPA National Homeland Security Research Center
• NHSRC Red Team
• Expertise on monitoring and detection of contaminants and
contaminant properties
• Hotline: 513-569-7990
– CDC Emergency Response Hotline
• Expertise on biological, chemical, and radiological contaminants
• 770-488-7100 (24 hours)
Return to Course Overview Slide
106
Gathering the Data: Subject Matter
Experts (cont.)
• Associations
– American Water Works Association
• Authoritative scientific and technological knowledge geared to the
drinking water community
• http://www.awwa.org/
• 1-800-926-7337
– Water Information Sharing and Analysis Center (WaterISAC)
• Gathers, analyzes and disseminates threat information that is
specific to the drinking water and wastewater community.
• http://www.waterisac.org/
• Universities and colleges
Return to Course Overview Slide
107
Contaminant Characterization
and Transport Worksheet
• Comprehensive data worksheet
for broad range of reported and
researched information
• Example provided in Module 5
of Response Protocol Toolbox
• Designed to capture most likely
information provided and
gathered for threat assessment
• Can be modified or expanded
to manage additional
information
Return to Course Overview Slide
108
Contaminant Information
Captured by the Worksheet
• Properties reported from the field, when available
–
–
–
–
•
•
•
•
•
Physical form and description
Taste and odor (if reported)
Environmental indicators of contamination
Amount of contaminant introduced
Consumer complaints or feedback
Witness accounts
Site characterization information
Reported changes in water quality parameters
Results of field tests conducted in response to the incident
Return to Course Overview Slide
109
Contaminant Information
Captured by the Worksheet (cont.)
• Details on lab analyses conducted in
response to the incident
– Critical for verifying the identity of the contaminant
– May be limited by detectability issues with some
contaminants
• Potential information to record and evaluate
– Analytical results
– Method used
– Sensitivity of method (minimum reporting limit
(MRL) or minimum level (ML)), if available
– Other data quality information critical to assessing
reliability of results (precision, recovery, positive
and negative controls, blanks, etc.)
– Other information reported by the laboratory that
may help verify the identity of the contaminant or
nature of the threat
Return to Course Overview Slide
110
Contaminant Information
Captured by the Worksheet (cont.)
• Contaminant properties
–
–
–
–
Solubility
Stability
Reactivity
Effect on water quality parameters
• Contaminant health effects
–
–
–
–
Exposure routes
Toxicity
Onset of symptoms
Available preventive measures or treatments
• Contaminant treatability
Return to Course Overview Slide
111
Part 7:
Data Use for
Consequence Analysis
Return to Course Overview Slide
112
What Now?
Individual contaminant
properties are simply
individual values in a
larger equation for the
potential public health
consequences of the
contamination
Fate and
Transport
Physical
Data
Infectivity
Data
?
Toxicity
Data
Chemical
Data
Exposure
Potential
Return to Course Overview Slide
113
Consequence Analysis
• During the initial assessment of the contaminant, much of
the information collected serves to respond to the two
primary consequence analysis components:
• The fate and transport of the contaminant
– Will the contaminant reach members of the population?
– If so, how many individuals will it potentially affect?
• The overall health effect of the contaminant
– If the contaminant does reach members of the population, will the
exposure cause an effect?
– What will the severity of the health effects be?
Return to Course Overview Slide
114
Fate and Transport
• Fate and transport of the contaminant can be assessed
using information collected for contaminant properties,
such as:
– Solubility
– Reactivity
– Hydrolysis
– Stability
– Volatility
– Adsorbtivity
• Other incident information is combined with the
information collected on contaminant properties to assess
contaminant fate and transport, including:
– Location of introduction
– Initial concentration of contaminant
– Public water system hydraulics and operation
Return to Course Overview Slide
115
Fate and Transport (cont.)
• Modeling tools to estimate spread of a contaminant
– Contaminant properties,
incident, and operational
information can be used
to drive modeling tools
such as PipelineNet
•
Simpler alternatives to estimate spread of a contaminant
– Using operational information potentially maintained by the water
utility, such as typical travel times from key nodes in a system to
large population centers or critical customers
Return to Course Overview Slide
116
Fate and Transport (cont.)
• Contaminant properties and operational information
– Can be used to determine whether the contamination may be
mitigated altogether by current treatment operations or conditions in
the distribution system
• After the area impacted by
the spread of contamination
has been estimated the
number of individuals
potentially affected must be
determined
Return to Course Overview Slide
117
Health Effects
• Fate and transport assessment is used with the health
effects assessment to complete the initial consequence
analysis
• Health effects of the contaminant can be assessed using
information collected for contaminant properties, such as:
– Formulation, species, or strain
– Toxicity or infectivity
– Severity of health effects
– Likely exposure routes
– Communicability
– Medical intervention
Infection-causing
Cryptosporidium
sporozoites
Return to Course Overview Slide
118
Health Effects (cont.)
• Toxicity properties
– MCL or LD50 are combined with the estimated concentration of the
contaminant at the tap to determine the likelihood of health effects
• Communicability information for pathogens
– Can be used to determine whether the health threat will end with a
do-not-drink order or continue even after this exposure route is
eliminated
• Treatability properties
– Combined with operational information to determine whether
contaminants, such as pathogens, will be inactivated or neutralized
Return to Course Overview Slide
119
Health Effects (cont.)
• Information on subpopulations
– Combined with the health effect information to assess whether
these populations will be affected, even if the majority of
consumers are not
• If sufficient information is not available, or there isn’t
sufficient time to find the information, it is best to make a
conservative estimate that severe public health impacts
are possible
Return to Course Overview Slide
120
Collect more
information
NO
Are
witness reports,
lab analyses, or other
properties
known?
Contaminant
Research
Prioritization
Tree for
Consequence
Analysis
Consult with experts or
use available tools to
reduce list of potential
contaminants
YES
T
AR
Has
ST
contaminant been
positively
identified?
NO
YES
NO
Research health
effects
YES
Has the public
been exposed?
NO
Research fate and
transport properties
Are
health effects
consistent with
symptoms?
Can
the contaminant be
contained before public
exposure?
YES
YES
Work with health
agency to determine
actions
Work with water utility to
determine action
YES
Return to Course Overview Slide
NO
NO
Research health
effects
Will
contaminant reach tap
at adverse public health
levels?
121
Potential Outcomes of Consequence Analysis
• Example 1:
– Contaminant is introduced at levels that would cause severe health
effects
– Degrades or is diluted to levels below concern before reaching any
consumers
– Work primarily with water utility to determine action
• Example 2:
– Contaminant introduced at levels that would cause severe health
effects
– Reaches segments of the population at levels of concern
– Consumer use is not consistent with effective exposure routes
– Work with both health agency and water utility to determine actions
Return to Course Overview Slide
122
Potential Outcomes of Consequence Analysis
(cont.)
• Example 3:
– Contaminant reaches segments of the population at levels that
cause severe health effects
– Consumers will be exposed
– Work with both health agency and water utility to determine
actions
• Example 4:
– Contaminant is introduced at levels that would not cause severe
health effects
– Decontamination results in long-term remediation, disruption in
service for extended periods of time
– Work primarily with water utility to determine actions
Return to Course Overview Slide
123
Secondary Consequence Analysis Issues
• Contaminant properties also will help respond to
secondary questions
– Remediation options for contaminant after initial response
– Assessment of impacts on the water system and consumers
• Contaminant properties also will help in identifying the
contaminant, if this is unknown
– Physical properties reported during the incident (taste, odor,
appearance)
– Potential for contaminant to affect water quality parameters
– Symptoms reported by health agencies
Return to Course Overview Slide
124
Part 8:
Example Contamination Scenario
(Other Examples Provided in Appendix)
Return to Course Overview Slide
125
Example: Cyanide
• A sensor located in a distribution system indicated a
dramatic drop in residual chlorine
• Tests confirmed the presence of cyanide in the drinking
water distribution system
– Samples collected from taps and throughout distribution system
– Positive samples, up to ½ -mile upstream at the distribution system
pump station, and up to 1- mile downstream near a residential area
• Hydrogen cyanide concentration in the water system = 40
mg/L
• The previously measured speed of water travel through the
distribution system is 10 ft/sec
• Summary of symptoms of those exposed: difficulty
breathing; flushed skin; nausea; vomiting
Return to Course Overview Slide
126
Critical Questions
• The following critical questions regarding cyanide properties
need to be answered:
– What methods, both field and laboratory, are available to measure
cyanide?
– Are current cyanide levels toxic enough to pose a threat to public
health?
– Which routes of exposure pose a threat to consumers?
– What is the fate and transport of cyanide through a drinking water
distribution system?
– What is the anticipated residence time of cyanide through the
treatment and the distribution system?
– Which treatment technologies can remove or detoxify cyanide?
– What reaction products of cyanide in finished drinking water pose
significant public health risks?
Return to Course Overview Slide
127
Sources of Information Identified
• The following potential sources were identified to collect
information on cyanide properties to support consequence
analysis:
– Material Safety Data Sheet for cyanide
• http://chppm-www.apgea.army.mil/dts/docs/detac.pdf
– National Institutes of Health TOXNET database
• http://toxnet.nlm.nih.gov/
– Centers for Disease Control and Prevention
• http://www.bt.cdc.gov/agent/cyanide/index.asp
– NIOSH Emergency Response Cards
• http://www.bt.cdc.gov/agent/cyanide/erc74-90-8.asp
– Subject Matter Experts from USEPA WSD and NHSRC
Return to Course Overview Slide
128
Information from First Source
• The Material Safety Data Sheet for cyanide was consulted
first, and the following information collected:
• Molecular weight: 27.03
• Vapor Pressure (mm Hg): 742 @ 25°C
• Boiling point: 25.7°C
• Adverse Health Effects
– Rapid acting, potentially deadly
– Prevents the cells of the body from using oxygen
– Exposure by inhalation, ingestion, or skin contact may result in
symptoms such as reddening of the eyes, flushing of the skin,
nausea
Return to Course Overview Slide
129
Information from First Source (cont.)
• Toxicity
–
–
–
–
–
LCt (inhalation, 0.5 min) = 2.000 mg-min/m3
LCt (inhalation, 30 min) = 20,600 mg-min/m3
NOAEL (inhalation) = 670 mg-min/m3
RfD (ingestion) = 0.750 mg/L (liquid)
LD50 (dermal) = 100 mg/kg (liquid)
• This information was entered on the Contaminant
Characterization and Transport Worksheet
• Additional information on fate and transport was needed,
and a second source consulted
Return to Course Overview Slide
130
Information from Second Source
• On the TOXNET site, a search for “cyanide” was
conducted by first selecting the “HSDB full record” option
• The following information was gathered from this source:
• Solubility
–
Highly soluble in water, but stable
• Stability
–
–
Forms equilibrium in water between CN- and HCN (aqueous)
Unstable with heat, alkaline materials
Return to Course Overview Slide
131
Information from Second Source (cont.)
• Persistence
–
–
Open system: Cyanide is highly volatile, and in the gaseous state, it
dissipates quickly in the air
Closed system: Does not dissipate in a pressurized pipe
• Reactivity
–
–
–
–
May react with chlorine to form CNCl, which is very toxic via multiple
exposure routes
Cyanide reactions sensitive to pH changes
May react violently with strong mineral acids
Polymerizes when heated and forms a potentially explosive solid
Return to Course Overview Slide
132
Information from Second Source (cont.)
•
Other properties
–
–
–
–
–
–
–
–
–
“Bitter almond” or pepper-like odor; not always detectable
Molecular weight: 27.03
Vapor Pressure (mm Hg): 742 @ 25°C
Volatilization half lives: Rivers: 3 days; Lakes: 3 days
Log Kow: -0.25
Henry’s Law constant: 1.33X10-4 atm-cu m/mol @ 25 deg C
Density: 0.7 g/cu cm
Water solubility = 1,000,000 mg/L @ 25°C
pKa of 9.2
Return to Course Overview Slide
133
Information from Second Source (cont.)
• Toxicity
–
–
–
–
–
–
LC50 inhalation (rat) 142 ppm/30 min
LC50 inhalation (dog) 300 ppm/3 min
LC50 subcutaneous (groundhog) 100 ug/kg
LC50 ip (intraperitoneal) (mouse) 2990 ug/kg
LC50 im (intramuscular) (mouse) 2700 ug/kg
LC50 iv (intravenous) (mouse) 990 ug/kg
• No LD50 for ingestion of cyanide was found
• This information also conflicted with the information found
on the MSDS
Return to Course Overview Slide
134
Information from Second Source (cont.)
• Additional toxicity information
– Determined from rat chronic oral
– NOAEL: 10.8 mg/kg/day cyanide converted to 11.2 mg/kg/day of
hydrogen cyanide
• Adverse Health Effects
– Rapid acting, potentially deadly
– Prevents the cells of the body from using oxygen
– Exposure by inhalation, ingestion, or skin contact may result in
symptoms such as reddening of the eyes, flushing of the skin,
nausea
– The human body can de-toxify cyanide, so exposure to a lethal dose
would need to occur over a relatively short time period
• This information was entered on the Contaminant
Characterization and Transport Worksheet
Return to Course Overview Slide
135
Information from Other Sources
• The Centers for Disease Control and Prevention site was
consulted, but no LD50 for cyanide ingestion was found
• EPA Subject Matter Expert contacted
– According to subject matter expert, the LD50 for cyanide ingestion
was approximately ~1.5 mg/kg
• NIOSH Emergency Response Card for hydrogen cyanide
evaluated for additional health effects descriptions
Return to Course Overview Slide
136
Use of Information Collected
• Health effect information was considered important
– Needed to determine worst consequence exposure route
– Needed to prepare for medical response
• The toxicity information was considered important
– Needed to confirm consequences of exposure and determine
concentration levels at which adverse effects are not likely to occur
• The solubility, fate, and reactivity information was
considered important for developing a treatment strategy
• Information on treatability was considered important
– Needed to determine a treatment method to eliminate the cyanide
Return to Course Overview Slide
137
Use of Information Collected (cont.)
• Other physio-chemical property information may prove
useful for planning the response and treatment
• Water Solubility
– Cyanide is water soluble and stable
– In a drinking water system, there is no place for HCN to go, so it will
stay in the water
– The higher the water solubility, the more likely the contaminant will
be available (soluble) in the water in both a closed and open system
Return to Course Overview Slide
138
Use of Information Collected (cont.)
• Fate
– Estimated volatilization half-lives for open systems: shows
cyanide can exist for up to 3 days in an open system
– Closed system: Expected to exist in a nearly equilibrium state
between CN- and HCN; especially in a pressurized pipe
• Could be dangerous if pipe pressure increases
• Possible explosion hazard as cyanide is trapped in the
pressurized distribution pipes
• Upon exit, may be further trapped in shower stalls, closed
bathrooms, containers, etc
• Reactivity
– Cyanide may react with treatment chemicals such as chlorine,
but the the product, CNCl is highly toxic.
Return to Course Overview Slide
139
Use of Information Collected (cont.)
• Log KOW
– Low
– In water, hydrogen cyanide is not expected to adsorb to suspended
solids and sediment in water
• Henry’s Law constant
– High
– Volatilization from water surfaces is expected to be an important fate
process; the contaminant will have a tendency to go into air once
exiting the closed system
• Density
– Cyanide gas is less dense than air, so it will rise
Return to Course Overview Slide
140
Use of Information Collected (cont.)
• Health Effects and Toxicity Information Selected
– Health Effects Descriptions (NIOSH emergency response cards,
CDC Bioterrorism provide the most succinct descriptions of
adverse health effects)
– The toxicity values collected varied widely; in this case, the lowest
(or most conservative value) was selected to ensure public safety
– LD50 (ingestion) = ~1.5 mg/kg (from EPA subject matter expert)
was most recent peer-reviewed data, the lowest LD50 value, and
the value is consistent with other data
Return to Course Overview Slide
141
Other Relevant Information
• Any breaches in security
• Additional operational information
• Affected population information
Return to Course Overview Slide
142
Consequence Analysis
• Toxicity Evaluation
– Based on the LD50 of 1.5 mg/kg, it was calculated that a
concentration of 50 mg/L would be needed to adversely affect an
infant drinking one 4 oz bottle of cyanide-contaminated water
– The cyanide concentration found in the water was 40 mg/L, which
does not exceed this 50 mg/L concentration, but adverse effects are
being reported indicating low level exposure
Return to Course Overview Slide
143
Consequence Analysis (cont.)
•
Total Estimated Exposure
– Because the water travels at 10 ft/sec and contamination was discovered
only 1 mile downstream of the affected population, it was assumed that
contamination was discovered quickly after occurrence and no more than
200 homes were affected before the system was shut off
•
Health Consequences
– Hydrogen cyanide is absorbed well by inhalation (showering) and can
produce death within minutes; therefore, immediate action should be taken
to treat victims for cyanide exposure
– Cyanide exposure is not contagious but persons whose clothing or skin is
contaminated with cyanide-containing solutions can secondarily contaminate
response personnel by direct contact or through off-gassing vapor;
secondary exposure should be avoided by following emergency response
guidance
Return to Course Overview Slide
144
Consequence Analysis (cont.)
• Emergency Action
– Shut off distribution system
– Evacuation of the premises
– Immediately treat exposed victims
• Recommended treatment options:
– Flush the system to a holding tank for subsequent treatment
– Chlorination at elevated pH levels will mineralize cyanide
Return to Course Overview Slide
145
Part 9:
Action Items and Learning Tools
Return to Course Overview Slide
146
Take Home Assignments
• Identify potential contaminant information resources and
subject matter experts in your home office. Make
arrangements for accessing these resources.
• Research information on one contaminant of each of the
major categories (pathogens, chemical agents,
radiochemical agents), using the data collection worksheet
• Research one contaminant to understand those properties
that would impact fate and transport in a distribution system
Return to Course Overview Slide
147
Take Home Assignments (cont.)
• Evaluate the health effects if one of the contaminants
reached the consumer’s tap at a concentration of 10
percent of the LD50
• Integrate the above into a consequence analysis for the
contaminant under a hypothetical scenario
Return to Course Overview Slide
148
Acknowledgments
• USEPA would like to thank the individuals who
contributed to their time and expertise to the
development, review and presentation of this training
–
–
–
–
–
–
–
–
–
Steve Allgeier
Michael Boykin
Alan Lindquist
Matthew Magnuson
Neal Nelson
Grace Robiou
Irwin Silverstein, AAAS Fellow
Ashley M. Smith
Stanley States, Pittsburgh Water and Sewer Authority
149
Part 10:
Appendix:
Example Scenarios for Other
Contaminants
Return to Course Overview Slide
150
Example: Bacillus anthracis
• Caller threatened to dump 55 gallons of anthrax into the
reservoir used as the source water for the surface water
treatment plant
• The utility uses a multiple barrier treatment process
including coagulation/flocculation, sedimentation and high
rate granular media filtration
• The measured distribution
system travel time through
the treatment process is 12
hours and between nearby
node and population center
is 4 hours
Return to Course Overview Slide
151
Critical Questions
• Based on the information provided, the following critical
questions regarding Bacillus anthracis properties need to
be answered:
– Are there immediate health and safety risks to first responders
and water utility staff if anthrax is present in the source water and
were to enter the treatment plant?
– What is the anticipated fate and transport of Bacillus anthracis
through treatment and the distribution system?
– Are utility treatment practices sufficient to remove or inactivate
Bacillus anthracis to mitigate or minimize the risk to drinking water
customers?
– What concentration levels of Bacillus anthracis in finished drinking
water pose significant public health risks?
Return to Course Overview Slide
152
Information Gathering: Bacillus anthracis
• The following outside sources were consulted to
characterize the contaminant and answer these questions:
– Centers for Disease Control and Prevention
http://www.bt.cdc.gov/agent/anthrax/index.asp
• HOTLINE: 888.246.2675
– The Journal of the American Medical Association
• http://jama.ama-assn.org/
– Subject matter experts from USEPA (WSD and NHSRC)
Return to Course Overview Slide
153
Information From First Source
• From the CDC Web site, the following information was
gathered:
• Health effects
– Symptoms and incubation period vary by route of exposure
– Lethality varies by route of exposure (inhalation most severe)
– If exposure or potential exposure is identified early, antibiotics or
vaccination can be used to prevent disease or lessen severity of
symptoms
• Size
– Spore size is approximately 1 µm x 2 µm
Return to Course Overview Slide
154
Information From First Source (cont.)
• This information was entered on the Contaminant
Characterization and Transport Worksheet
• However, no information on fate and transport, stability, or
toxicity was found from this source, but the Web site
pointed to JAMA Web site for additional public health
information
Return to Course Overview Slide
155
Information From Second Source
• From the JAMA Web site, the following information was
gathered:
• Health Effects
– Inhalational anthrax is expected to account for most morbidity and
essentially all mortality following the use of anthrax as an
aerosolized biological weapon
• Virulence
– Estimate for humans: LD50 2500 to 55,000 inhaled anthrax spores
(based on primate data)
• This information was entered on the Contaminant
Characterization and Transport Worksheet
• However, no information on fate and transport or stability
was found from this source, so additional sources were
consulted
Return to Course Overview Slide
156
Information From Third Source
• From the EPA subject matter experts, the following
information was gathered:
• Stability
– Likely to be stable in water long enough to pose a threat
– Spores will survive longer and are more resistant to chlorine than are
vegetative cells
• Toxicity
– Vegetative cells are more infective than spores via ingestion
Return to Course Overview Slide
157
Information From Third Source (cont.)
• This information was entered on the Contaminant
Characterization and Transport Worksheet
• Although additional information was still needed, it was
clear that actions needed to be taken and a consequence
analysis was performed using the data that had been
gathered
Return to Course Overview Slide
158
Use of Information Collected
• Information collected from three sources was then
evaluated based on the two components of consequence
analysis, fate and transport and health effects
• Properties related to fate and transport
– Stability: Spores will survive longer and are more resistant than
vegetative cells to chlorine
– Size: Spores are smaller than many filters: 1 µm x 2 µm
Return to Course Overview Slide
159
Use of Information Collected (cont.)
• Properties related to health effects
– Exposure and severity
• Symptoms and incubation period vary by route of exposure
• Lethality varies by route of exposure (inhalation most severe)
• If exposure or potential exposure is identified early, antibiotics
or vaccination can be used to prevent disease or lessen
severity of symptoms
– Virulence
• Infective dose: 6,000 inhaled anthrax spores
• LD50 2500 to 55,000 inhaled anthrax spores (based on primate
data)
• Vegetative cells are more infective than spores via ingestion
Return to Course Overview Slide
160
Other Relevant Information
• Information from the incident
• Additional operational information
• Affected population information
Return to Course Overview Slide
161
Consequence Analysis
• Sampling, analysis and additional
information about the threat
confirmed that anthrax was
introduced into the source water
and it is estimated that up to 500
million spores entered the
treatment plant
• The utility could expect a 3-log
removal based on existing
treatment processes using
conventional filtration
• The estimated quantity of anthrax
spores released into the
distribution system would be
500,000 spores
Return to Course Overview Slide
162
Consequence Analysis (cont.)
• Laboratory results for
samples taken at various
points along the suspected
travel route of the slug of
anthrax will help to confirm
the concentration of the
contaminant
• The drinking water utility
should continue to work
closely with public health
officials
Return to Course Overview Slide
163
Example: Sulfur Mustard
• Based on information in the incident report, an estimated 10
kg of sulfur mustard was thought to be introduced into a
primary storage tank of a water treatment plant based on
information provided about the incident
• The tank contains 4 million liters of water
• The water temperature in the tank is approximately 70° F
• The water in the tank will take 12 hours to reach the nearest
consumer tap
• The sampling results indicated:
– No measurable amounts of sulfur mustard were found in the storage
tank
– Sulfur mustard was not detected downstream in the distribution
system; thioglycol concentrations were detected
– MDL of method used was reported as 50 µ/L
Return to Course Overview Slide
164
Critical Questions
• Based on the information provided, the following critical
questions regarding sulfur mustard properties need to be
answered:
– Are sulfur mustard levels at the tap likely to be toxic enough to
issue a “stop-use” order?
– Where would the sulfur mustard be within the distribution system?
– Will water treatment technologies currently in use be effective at
detoxifying or degrading mustard gas?
Return to Course Overview Slide
165
Sources of Information Identified
• The following potential sources are identified to collect
information on sulfur mustard properties to support
consequence analysis if the contaminant is introduced into
the system:
– U.S. Army Chemical Materials Agency
• http://www.cma.army.mil/home.aspx
– Agency for Toxic Substances and Disease Registry (ATSDR)
• http://www.atsdr.cdc.gov/tfactsd3.html
– Centers for Disease Control and Prevention (CDC)
• http://www.bt.cdc.gov/agent/sulfurmustard/index.asp
Return to Course Overview Slide
166
Information from First Source
• Information on the U.S. Army Chemical Materials Agency
site was evaluated, but the information provided on the
Web site was very general
• However, a point of contact was provided for additional
information
• The point of contact was able to provide information on
who to contact at the nearby Army facility for further action
• This information was entered on a Contaminant
Characterization and Transport Worksheet
• Additional sources were consulted to find information on
health effects and fate and transport
Return to Course Overview Slide
167
Information from Second Source
• On the ATSDR Web site, a lengthy toxicological profile of
sulfur mustard was identified and reviewed, providing
information on many of the properties of interest
• Color and Odor
– Pure liquid is colorless and odorless
– Appears brown and has a garlic-like smell when mixed with other
chemicals
• Solubility
– Limited in water
• 920 mg/L at 22°C
• 684 mg/L at 25°C
– Dissolves easily in oils, fats, and other solvents
Return to Course Overview Slide
168
Information from Second Source (cont.)
• Henry’s law constant
– 1.87 x 10-5 or 2.4 x 10-5 atm-m3/mol
• Hydrolysis of sulfur mustard is relatively rapid in water once
dissolved
– Hydrolysis half-life ranges from 1.5 minutes at 40°C to 158 minutes
at 6°C
– Primary hydrolysis products include mustard chlorohydrin,
thiodiglycol, and hydrochloric acid
– Mustard chlorohydrin hydrolyses faster than sulfur mustard
– Thiodiglycol is not susceptible to hydrolysis
– Although not well documented, it has been reported that sulfur
mustard immersed in water has been found to be active and toxic;
this may be the result of a protective oxidative coating forming on the
outside of microscopic particles of sulfur mustard
Return to Course Overview Slide
169
Information from Second Source (cont.)
• Oxidation
– Mustard gas is oxidized in aqueous solution to mustard sulfoxide
and mustard sulfone by agents such as hydrogen peroxide and
ozone as well as chlorine and hypochlorites
– Mustard sulfoxide is extremely stable, and not prone to
hydrolysis; it is slightly toxic
• Reactivity
– Bleaching-powder and chloramines react violently and form nonpoisonous oxidation products
– On contact with acid or acid vapors, it emits highly toxic fumes of
vapors of sulfur and chlorine
Return to Course Overview Slide
170
Information from Second Source (cont.)
• Toxicity Values
– MRL of 0.0005 mg/kg/day for acute-duration exposure (14 days or
less)
– Inhalation LCt50 for humans is 900 mg-minute/m3 for 10-minute
exposure
• Estimated for humans by Army’s Chemical Defense Equipment
Process Action Team by averaging toxicity data from several
animal species
– LD50 for skin exposure is 100 mg/kg
• Value provided by Army without details on how it was derived
– Oral LD50 of 0.7 mg/kg
• Estimated for humans by the Army but no information was
provided on how it was derived
Return to Course Overview Slide
171
Information from Second Source (cont.)
•
Health Effects
– Skin absorption will result in skin burns and blisters
– Eye contact may make the eyes burn and eyelids swell
– Inhalation may result in coughing, bronchitis, and long-term respiratory
disease
• Hoarseness and irritation of the nasal mucus may develop 12 hours to 2
days after exposure to 12-70 mg-minute/m3; recovery may occur after
approximately 2 weeks
• Exposure to 1,000 mg-minute/m3 may result in injuries progressing to
edema in the pharynx and tracheobronchial tree, followed by death due
to severe edema, secondary infection or necrotic bronchopneumonia
– Symptoms may not occur for 2 to 24 hours
– Symptoms that occur get progressively worse
– Effects of long term or repeated exposure: second/third degree burns,
scarring, chronic respiratory disease, permanent blindness, death
•
This information was entered or updated on the Contaminant
Characterization and Transport Worksheet
•
Additional information was desired for oxidation and reactivity
Return to Course Overview Slide
172
Information from Third Source
• The CDC Bioterrorism Web site was accessed, and the
information reviewed
• It was found that much of the same information found in
ATSDR was also posted on this site, with no new
information on oxidation or reactivity
• Although additional information was still needed, a
consequence analysis was performed using the data that
had been gathered
Return to Course Overview Slide
173
Use of Information Gathered
• MRLs and other toxicity values were considered important
– Needed for comparison to the measured values in the storage tank
and distribution system
– Assessment of the effect of the contaminant at the concentration the
population potentially would be exposed to it
• Health effect information was considered important
– Determine if any health effects seen in the public are a result of the
contamination event
– Determine likely adverse effects if concentrations were high
– Prepare for medical response if necessary
Return to Course Overview Slide
174
Use of Information Gathered (cont.)
• Information on hydrolysis was considered important to
determine how quickly sulfur mustard would break down,
if it was introduced
– The hydrolysis half-life of 1.5 to 158 minutes indicates the
hydrolysis of sulfur mustard takes place quickly once it is
dissolved
– Because the breakdown product, thiodiglycol, is not susceptible
to hydrolysis, this was identified as a potential analyte for
monitoring of the system
• The solubility in water was considered important
because hydrolysis will not take place until sulfur
mustard dissolved
Return to Course Overview Slide
175
Use of Information Gathered (cont.)
• Because the sulfur mustard may be colorless and odorless,
color and odor were not considered useful for determining
whether a contamination event had occurred
• Henry’s law constant, used to determine volatilization, was
not considered useful due to the closed storage tank, which
had little headspace, and distribution system in this situation
Return to Course Overview Slide
176
Other Relevant Information
• Information from the incident
• Additional operational information
• Affected populations
Return to Course Overview Slide
177
Consequence Analysis
• If 10 kg of sulfur mustard were introduced into 4 million
liters of water:
– 10 kg/(4x106 L) = 2.5 x 10-6 kg/L = 2.5 x 10-3 g/L = 2.5 mg/L
• This is well below the solubility of sulfur mustard in the
system of approximately 1000 mg/L
• All of the sulfur mustard will have dissolved in the tank
and entered the distribution system
Return to Course Overview Slide
178
Consequence Analysis (cont.)
• The oral LD50 for sulfur mustard of 0.7 mg/kg translates to
49 mg total dose for an average, 70 kg person
• 20 L of contaminated water would need to be ingested to
get the LD50
• Although this is not likely, toxicity is not linear with
concentration, so drinking 1 L containing 2.5 mg/L might
still kill some portion of the population, but not 50 percent
Return to Course Overview Slide
179
Consequence Analysis (cont.)
• Due to the hydrolysis, even this dose is unlikely to reach the public
• If the half-life due to hydrolysis is approximately 60 minutes at the
temperature in the system, the contaminant would undergo 12 halflives in 12 hours
• This equates to 2.5/122 = 0.0006 mg/L = 0.6 Fg/L sulfur mustard at
the nearest consumer’s tap
• Health effects due to sulfur mustard, if any, should be mild
• Sulfur mustard in chlorine water will cause oxidation which results in
mustard sulfoxide; mustard sulfoxide is extremely stable to hydrolysis
and slightly toxic. Additional toxicity and health effects data should be
collected.
• Thiodiglycol is a precursor for sulfur mustards and is completely
soluble in water; inhalation and skin contact are the primary routes of
exposure. Based on single exposure animal tests, thiodiglycol is
considered non-toxic if swallowed, slightly irritating to eyes, and
practically non-irritating to skin.
Return to Course Overview Slide
180
Example: Ricin
• An approximate concentration of 100 mg/L of Ricin is
detected in public drinking water
• Summary of victim symptoms include nausea, diarrhea,
and weight loss, and reports of coughing and difficulty
breathing in the shower
• Drinking water distribution map noted locations of
incidents
• The rate of water moving through the distribution system
was used to determine the spread of contamination
• Sensitive population is served by municipal water utility
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181
Critical Questions
• Based on the preliminary results, the following questions
regarding ricin properties need to be answered:
– How serious are the consequences of ricin exposure?
– What is the anticipated fate and transport of ricin in the
distribution system?
– Because ricin has already reached the public via finished water,
what additional water treatment can the utility use to mitigate
further exposure?
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182
Sources of Information Identified
• The following potential sources are identified to collect
information on ricin properties to support consequence
analysis if the contaminant is introduced into the system:
– Centers for Disease Control and Prevention
http://www.bt.cdc.gov/agent/ricin/index.asp
– National Institutes of Health TOXNET database
http://toxnet.nlm.nih.gov/
– Subject mater experts from USEPA (WSD and NHSRC)
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183
Information from First Source
• On the CDC Web site, several resources were available
on ricin’s health impacts and toxicity
• Health Effects
– Symptoms occur within 4 to 12 hours if inhaled or swallowed
– Symptoms following ingestion include abdominal pain, vomiting,
and diarrhea (sometimes bloody)
– Symptoms following inhalation would be respiratory distress
(difficulty breathing), fever, cough, nausea, convulsions, paralysis
– Potential exposure to lethal doses through cuts in the skin,
bleeding gums, etc.
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184
Information from First Source (cont.)
• Toxicity
– Inhalation and intravenous
injection are the most lethal
(5–10 µg/kg); not well
absorbed through the
digestive tract or through
the skin
– LD50: 5 mg/kg
– Possibility for 1 mg to kill an
adult via direct injection
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185
Information from First Source (cont.)
• CDC’s Web site provided only general information on
physical properties of ricin
• Fate and Transport
– Powder form disperses readily into all media
• Stability
– Stable in ambient conditions and temperature extremes in water
– Resistant to chlorine
• Solubility
– Freely soluble in water (20°C) and dilute acetic acid
– Soluble: 10 percent NaCl solution
• This information was entered on the Contaminant
Characterization and Transport Worksheet
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186
Information from Second Source
• The TOXNET database provided more information on
toxicity and adverse health effects
• Adverse Health effects:
– Symptoms of Ricin exposure: weight loss, diarrhea,
convulsions, alternating periods of paralysis, then death
– Exposure routes: Toxic by ingestion, small particle in cut or
abrasion may prove fatal
• Toxicity
– Probable oral human lethal dose: a taste (less than 7 drops) for
a 70 kg person (150 lbs)
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187
Information from Second Source (cont.)
• TOXNET provided much the same information on physical
properties, such as stability, and solubility found on CDC’s
Web site
• Additional sources were consulted to find information on
fate and transport and other physical properties
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188
Information from Third Source
• EPA subject matter expert knowledge was sought out to
provide confirmation of data found and fill gaps
• Toxicity
– Oral LD50 values can be as low as 1 mg/kg
• Other Physical Properties: very little is known
–
–
–
–
Boiling Point: Decomposes
Vapor Pressure (20°C): Negligible
Volatility: Negligible
Solubility: In an acid and a base
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189
Information from Third Source (cont.)
• Treatability
– Ricin is detoxified in 10 minutes at 176°F (80°C), and in 1 hour at
122°F (50°C)
• This information was entered on the Contaminant
Characterization and Transport Worksheet
• Although additional information was still needed, and a
consequence analysis was performed using the data that
had been gathered
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190
Use of Information Gathered
• Health effect information was considered important
– Needed to determine worst consequence exposure route
– Needed to prepare for medical response
• The toxicity information was considered important
– Needed to confirm consequences of exposure
• The solubility in water was considered important
– Needed to confirm whether ricin remains stable in water
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191
Use of Information Gathered (cont.)
• Information on treatability was considered important
– Needed to determine whether standard water treatment would
significantly degrade ricin
– Needed to understand potential drawbacks of emergency water
treatment such as boiling and its increase in potential exposure
(aerosols)
• Half-life in water and other information would have been
useful but not available
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192
Other Relevant Information
• 166 mg/L concentration (calculated using 5 mg/kg lethal
dose) is what would have to be found to be a lethal
concentration for an average 70 kg person in the
drinking water
• Operational Information
• Affected Population Information
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193
Consequence Analysis: Ricin
• Health consequences
– The concentration found doesn’t exceed the fatal concentration
– People are suffering adverse affects
– Because the tested concentration is in the same order of magnitude as
LD50, it could be potentially fatal
– Issuing a “boil water” advisory could expose the public to toxic vapors
before the ricin is decomposed
• Fate and transport
– The extent of contamination reached a sensitive population area
• Treatability
– Chlorine levels in the finished water do not reduce ricin toxicity
– Effects of other treatment technologies on ricin are not known
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194
Example: Cesium-137
• A white crystalline powder was introduced into an opened
entry port at a remote pump station
• Initial radioactivity screening of the area with Geiger
counters indicated the white powder was radioactive, with
high levels of beta/gamma activity
• Screens for microbial or chemical contaminants were
negative
• The previously measured distribution system travel time
between the inlet used to add the contaminant and the
nearest population center is 180 minutes
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195
Example: Cesium-137 (cont.)
• Follow-up field screening of the white powder and bags
with a portable gamma detector initially detected gamma
activity. Laboratory analysis results positively identified
the substance as Cs-137.
– Four water samples taken from sampling points with increasing
distance from the site of the contamination were further
characterized on an expedited basis at a radiochemistry
laboratory certified for gross beta, Cs-137, and gamma screen
analyses
– These measurements indicate the majority of beta radiation from
the sample is from Cs-137 at a concentration level of 130 + 13
pCi/L
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196
Critical Questions
• Based on the information provided, the following critical
questions regarding Cs-137 properties need to be answered:
– What concentration levels of Cs-137 in finished drinking water can
be tolerated before public health is endangered and a stop-use order
must be issued?
– What are the short- and long-term health effects of the consumption
of Cs-137 contaminated drinking water?
– Will it decay away in sufficient time so not to require treatment?
– What is the anticipated fate and transport of the radionuclide in the
distribution system?
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197
Sources of Information Identified
• The following potential sources were consulted to
characterize the contaminant and answer these questions:
– EPA Radionuclides Fact Sheets and Contaminants MCLs
• http://www.epa.gov/radiation/radionuclides/cesium.htm
• http://www.epa.gov/safewater/mcl.html#mcls
– Agency for Toxic Substances and Disease Registry (ATSDR)
• http://www.atsdr.cdc.gov/toxprofiles/tp157.html
– CDC Radiation Emergency Page
• http://www.bt.cdc.gov/radiation/index.asp
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198
Information from First Source
• At the EPA Web site, the following information was
found:
• General properties
– A soft malleable silver-white metal
– A liquid near room temperatures (83oF)
• Health effects of Cs-137 exposure
– At low exposure levels, increases in cancer rates are observed
– At high exposure levels, burns and deaths can result
• Half-life of Cs-137
– 30 years
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199
Information from First Source (cont.)
• Fate and transport information
– Moves easily through the environment
– No specific information was found
• MCL of 4 mRem/yr
• This information was entered on a Contaminant
Characterization and Transport Worksheet
• Because no specific fate and transport data or information
on chemical or physical properties was found from this
source, additional sources were consulted
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200
Information from Second Source
• On the ATSDR Web site, a toxicological profile of cesium
was identified and reviewed, providing information on many
of the properties of interest
• Common chemical forms of Cesium-137 and their chemical
properties
– Chlorides are the most common forms found
– Can also exist as carbonates, hydroxides, or oxides
– Chemical and physical data for these chemical forms
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201
Information from Second Source (cont.)
• Environmental Fate and Partitioning
– In solution with water, Cs-137 will be present as a Cs1+ ion
– Most Cs-137 will be adsorbed onto surfaces of suspended solids,
eventually settling
– Will bioaccumulate in both terrestrial and aquatic food chains
– Waters with a high humic content and potassium levels increase
partitioning Cs-137 into the food chains or sediments
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202
Information from the Second Source (cont.)
• Health effects of Cs-137 exposure
– Systemic Toxicity
• All systems depressed
• Higher doses can cause sterility
– Cancers often occur in exposed populations due to chromosomal
damage
– Children are the most susceptible population
– Exposure limits reported
• EPA MCL for Cs-137 is 4 mRem/yr total body dose, equivalent to
an activity concentration of 200 pCi/L of Cs-137
• NOAEL = 200 rads Total Body Dose
• LOAEL = 350 rads Total Body Dose
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203
Information from the Second Source (cont.)
• Types of radioactivity emitted by Cs-137
– Can emit beta particles with two different energies
• 0.1734 and 0.4346 MeV
– Gamma particle with an energy of 661.67 keV emitted when one
immediate daughter, Ba-137m, decays to a stable form; Ba-137
• This information was entered or updated on the
Contaminant Characterization and Transport Worksheet
• Essential information was found in the two references, so
the third source was not consulted
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204
Fate and Transport and Health Effects
• Information collected from the two sources was evaluated
based on the two components of consequence analysis
• Properties related to fate and transport
– Solubility
• In a chloride form, Cs-137 forms a white, crystalline powder that
is highly soluble in water (1.8 kg/L)
• Cesium halides dissociate much like sodium and potassium, and
exist as Cs+1 ions in solution
– Reactivity
• As with the other alkali metals, cesium in a water solution is
relatively unreactive
– Absorptivity
• Cs-137 is highly absorbed by mineral surfaces of suspended
solids that eventually become sediments
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205
Fate and Transport and Health Effects (cont.)
• Properties related to health effects
– Half-life
• 30.17 years
– Exposure and severity
• Short term chronic external exposure can cause burns, acute
radiation sickness, and even death
• NOAEL is 200 rads, and LOAEL is 350 rads
• Risks at lower levels still exist, including increased cancer risks
– Emergency Action Trigger
• Water activity concentration limit above which a stop-use order is
required is 4 mRem/yr (equivalent to 200 pCi/L)
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206
Other Relevant Information
• Information reported from the incident
• Operational information
• Affected population information
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207
Consequence Analysis
• Based on flow rate, mixing models for the Cs-137 in water,
and the characteristics of the water system, the contaminant
will spread to the nearest population center in 180 minutes
• Based on the laboratory results, the concentration at the
consumer’s tap is likely to be within 10 percent of 130 pCi/L.
This level is at least 53 pCi/L below the beta particle activity
MCL for Cs-137
• Although no general stop-use order needs to be issued,
children should not use the water until the contamination
can be remediated
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208