Transcript Slide 1

CHAPTER 2
RISK CONCEPTS
Chapter 2
This chapter will focus on the basic concept of
environmental risk and risk assessment as applied to
a chemical’s manufacturing, processing, and the
impact of exposure to these chemicals on human
health or the environment.
INTRODUCTION TO :
Risk Concepts
Risk Assessment
Environmental Law and Regulations
Ethics
Risk Concepts
Risk = f (Hazard, Exposure)
Risk : Probability for an individual to suffer an
adverse effect from an event.
Hazard : Potential for a substance or situation to
cause harm or adverse effects to environment
and/or humans.
Exposure : Magnitude and length of time an
individual organism is put under a certain
constraint (hazard).
The Risk-Hazard-Exposure-Vulnerability Relationship
EXPOSURE
RISK
VULNERABILITY
HAZARD
Source:http://www.ga.gov.au/pdf/GA1421.pdf
Example
I. Hazardous substances and risk
Potassium Dichromate is a highly toxic carcinogenic
chemical. It is used in some techniques to analyse
exhaled breath for alcohol content. However for this
purpose it is sealed in a tube, and does not become
airborne when air is drawn over it.
Therefore, although it is a highly hazardous
substance, if it is use as described, it does not present
any risk to the subject.
Source:http://www.agius.com/hew/resource/hazard.htm
Example
II. Non hazardous substances and risk
Flour would not be considered as a hazardous
substance. However, people exposed over a period of
time to airborne flour dust and/or dust by skin contact
could develop dermatitis, conjunctivitis, rhinitis and
even asthma.
Thus, long exposure to a low hazard agent may
result in a substantial risk and low exposure to a
highly hazardous agent may result in a low risk.
Source:http://www.agius.com/hew/resource/hazard.htm
Exposure Pathways Include :
• Occupational Exposure (occurs in the workplace)
• Consumer Exposure (to products)
• Environmental Exposure
Direct (exposure to air, soil and water)
Indirect (i.e. contamination through the food
chain)
Indirect Exposure Pathways
Source:http://www.chem.unep.ch/irptc/Publications/riskasse/A2A4Txtab.PDF
Types of Risk
Voluntary Risks
Involuntary Risks
A consequence of
actions taken out
of necessity or by
choice. (e.g.,
driving a car, riding
a motorcycle,
smoking cigarettes)
A consequence of
uncontrollable
actions performed
by others. (ex.
exposure to
environmental
contaminants)
Natural
Disasters
These include
floods, hurricanes,
earthquakes and
other disasters that
are beyond human
control.
Source:http://risk.lsd.ornl.gov/minicourse/rap_q1.shtml
Risk Assessment
“Risk assessment should estimate adverse impacts
to health or the environment and determine whether
these impacts pose a serious threat.” National
Research Council (USA).
Goal: To understand, quantify and communicate risk
issues as comprehe nsively as possible.
Tools: Laws
substances
and
regulations
concerning
the
Risk Assessment Steps
Hazard Assessment
(Identification)
Dose-Response
Assessment
Exposure
Assessment
Risk Characterization
*Risk
Management
*Normaly not included in
risk assessment.
Source : Environmental Engineering and Science, Allen and Shonnard, pp.123
Hazard Assessment
“Determining the potential and/or known adverse
effects of a given material”
Adverse health effects
related to chemical
exposure:
• Cancer
• Endocrine disruptions
• Reproductive toxicity
Hazard estimation :
• Structure Activity
Relationships (SAR)
• Based on chemicalspecific laboratories
• From reference
databases
Toxicological Hazards
Substances that pose toxicological hazards
can be divided into four categories:
Hazard
Classification of Substances
SPECIAL
Carcinogenic; Mutagenic; Toxic to Reproduction.
Respiratory Sensitisers.
HIGH
Very toxic; Toxic; Skin Sensitisers; Corrosive.
MEDIUM
Harmful
LOW
Substances examined but not meeting the criteria
of the other hazard categories.
Carcinogenic Assessments
Genotoxic vs. Non-Genotoxic Carcinogens
• A Genotoxic Carcinogen “always” causes cancer
regardless of its quantity or concentration – one
molecule could alter DNA and cause a mutation.
• A Non-Genotoxic Carcinogen has a “safe”
threshold quantity.
• If the nature (genotoxicity) of the substance is
unknown, the carcinogen is assumed to be
genotoxic.
Carcinogenic Substances Classification
• Group A : Carcinogenic to Humans
• Group B1 : Probably Carcinogenic to Humans based on
limited human evidence of carcinogenocity
• Group B2 : Probably Carcinogenic to Humans based on
sufficient animal evidence, but inadequate human
evidence
• Group C : Possibly Carcinogenic to Humans
• Group D : Not classifiable for Human Carcinogenicity
• Group E : Evidence of Non-Carcinogenicity for Humans
Example of a Carcinogenic Chemical
Mercury (Hg) is an example of an air toxic
Acute (short-term) exposure to high levels of mercury in
humans results in central nervous system (CNS) damages
which can result in, among others, tremors and mood
changes.
Chronic (long-term) exposure to high levels of mercury in
humans also affects the CNS, with effects such as erethism
(increase excitability), irritability, excessive shyness, and
tremors.
Source: www.osha.gov
Non-Carcinogenic (Toxic) Effects
Assumed to have a dose or exposure threshold
Measurements :
• Rf D (Reference Dose) [=] mg pollutant/kg
body weight/day
• Rf C (Reference Concentration) [=] mg/m3
Derived from NOAEL (Non Observed Adverse Effect
Level) and LOAEL (Lowest Observed Adverse Effect
Level) using some uncertainty factors
Non-Carcinogenic Effects
How to Calculate...
Rf D =
Where:
NOAEL
FA FH FS FL FD
FA is an adjustment factor to extrapolate from animal to human
populations.
FH is an adjustment factor for differences in human
susceptability.
FS is an adjustment factor used when data are obtained from
subchronic studies.
FL is an adjustment factor applied when the LOAEL is used
instead of the NOAEL.
FD is an adjustment factor applied when the data set is dubious
or incomplete.
Example : Reference Dose Calculation
For 4-Clorophenol, 2.58 mg/kg-day is considered a
LOAEL, and 1.28 mg/kg-day is considered a NOAEL.
In rats, liver effects were assessed by the determination
of liver weights.
1. Using the NOAEL
Rf D =
NOAEL
FA FH FS
=
1.28 mg/kg-day
= 0.00128 mg/kg-day
10 x 10 x 10
2. Using the LOAEL
Rf D =
LOAEL
=
FA FH FS FL
2.58 mg/kg-day
10 x 10 x 10 x 10
= 0.000258 mg/kg-day
Source: http://www.atsdr.cdc.gov/toxprofiles/tp107-a.pdf
Hazard Assessment: Canadian References
• WHMIS (Workplace Hazardous Materials Information System)
http://www.hc-sc.gc.ca/hecs-sesc/whmis/index.htm
• CanOSH (Canada’s National Occupational Health and Safety)
http://www.canoshweb.org/en
• CCOHS (Canadian Centre for Occupational Health and Safety )
http://www.ccohs.ca
• MSDS (Material Safety Data Sheets)
http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss
Hazard Assessment: American References
• NIOSH (National Institute for Occupational Safety and Health)
http://www.cdc.gov/niosh/homepage.html
• ATSDR (American for Toxic Substances and Diesease Registery)
http://www.atsdr.cdc.gov
• IRIS (Integrated Risk Information System)
http://www.epa.gov/ngispgm3/iris/index.html
• National Library of Medicine
Hazardous Substances Data Bank
http://chem.sis.nlm.nih.gov/hsdb/
Toxnet
http://sis.nlm.nih.gov/sis1/
Hazard Assessment: Mexican References
• Information about Health and Safety Laws
http://www.salud.gob.mx/unidades/dgaj/
http://www.salud.gob.mx
• Information about environmental laws and regulations
http://www.semarnat.gob.mx/wps/portal
Dose-Response Assessments
Characterizing the relationship between
the quantities (dose) and resulting adverse
effects (response) of a given material.
Requires dose-response curves that
demonstrate the effects of chronic toxicity
Dose - Response Curves
 X-axis plots the
concentration
 Y-axis plots the
response
 dose-response
curves typically
follow this shape
Exposure Assessments
“Determining not only the size and nature of the
population affected by a potential exposure but also the
length of time during which they may be exposed.”
Normally the exposure assessed will be an
external exposure.
Where the conclusion is that this level is "of
concern", it may be necessary to determine
the internal exposure.
Risk Characterization
“Estimating the magnitude of the adverse effects on
given populations by compiling all the data from the
three previous steps.”
This stage involves the quantitation of the
risk following consideration of the
exposure and the dose-response (effect)
relationships.
The
function of the system is to regulate a wide range of biological
.
processes, including:
•
•
•
•
Control of Blood Sugar.
Growth and Function of Reproductive Systems.
Regulation of Metabolism.
Brain and Nervous System Development.
Disruptions in hormonal balance at critical life stages may have
long-lasting effects.
Source:http://www.epa.gov/ORD/NRMRL/EDC/
Risk Management
“Identifying, evaluating, selecting and implementing
actions to reduce risk to populations and environments.”
This step is a scientific attempt to identify and estimate the
true risks, by considering the :
• Hazard(s)
• Dose-Response Relationship
• Risk Characterization.
Potential solutions are then proposed, selected and
implemented in order to minimize the risks.
Environmental Law and Regulations
Why are these laws made?
- To protect human health as well as the
environment by placing limits on the concentration
and quantity of different chemicals in manufacturing
waste streams.
- Recently, laws and regulations encouraging
pollution prevention have been put in place to
encourage waste minimization instead of controlling
the regulated substances.
Environmental Law and Regulations
Where can we find them?
North American Commission for Environmental Cooperation
http://www.cec.org/home/index.cfm?varlan=english
México  Semarnat
http://www.semarnat.gob.mx/wps/portal
Canada  Canadian Environmental Protection Act
http://laws.justice.gc.ca/en/C-15.31/
 General Index to Laws
http://laws.justice.gc.ca/en/index.html
USA  General Index to Laws
http://www.epa.gov/epahome/rules.html
Engineering Ethics
“In addition to the laws and regulations by which chemical
engineers should abide, there exist codes of ethics.”
These codes of ethics can be found :
American Institute of Chemical Engineers (AIChE)
http://www.aiche.org/about/ethicscode.htm
Canadian Society for Chemical Engineers (CSChE)
http://www.chemeng.ca/ethics
Instituto Mexicano de Ingenieros Quimico (IMIQ)
http://www.imiq.org/
The Online Ethics Center for Engineereing and Science
http://www.onlineethics.org/