Transcript Recreational Water Quality and Health ENVR 890 Mark D. Sobsey Spring, 2007 Health Risks from Recreational Water • What are the health risks from recreational.

Recreational Water Quality
and Health
ENVR 890
Mark D. Sobsey
Spring, 2007
Health Risks from Recreational Water
• What are the health risks from recreational water
and how important are microbial risks?
• Health risks:
– Microbial or infectious disease risks
• enteric, respiratory, skin, eyes, ears, etc.
• AFRs: accidental fecal releases and purposeful
introduction of feces (wash the diaper in the pool!)
• Sewage, combined sewer overflows, etc.
• Animal fecal wastes: waterfowl, etc.
• Bather load and microbial shedding
Health Risks from Recreational Water
• Drownings
• Spinal and other related “sports” injuries
– Diving
– Falling (slipping)
• Boating accidents
• Chemical exposures
WHO Health Risk Based Approach to
Recreational Water Quality
• Combined use of sanitary
assessment or inspection and
measurement of water quality
• Provides data on possible pollution
sources in a recreational water area
and numerical information on actual
level of fecal pollution
• Combine these elements to provide
a basis for a robust, graded,
classification
• Grade beaches to support informed personal choice
• Provide on-site guidance to users on relative safety;
• Assist in identifying and promoting effective management interventions
• Provide an assessment of regulatory compliance.
Simplified Framework and Decision Tree for
Recreational Water Management
WHO Risk Based Framework: Application to
Recreational Water
• Two components to management:
– (a) qualitative ranking of fecal
loading in recreational water
environment (sanitary inspection),
and
– (b) direct measurement of fecal
indicator
• Provide a system to account for the
impact of actions to discourage water
use during periods, or in areas, of
higher risk (e.g., rainfall or
uncontrolled sewage contamination)
WHO
Guideline
Values For
Microbial
Quality of
Recreational
Waters
Epidemiological Studies of Recreational Water
Quality: Evidence Base
• Many studies show causal relationships between
gastrointestinal symptoms and water quality as
measured by indicator bacteria numbers (Prüss,1998)
• Strong and consistent associations reported, with
temporal and dose–response relationships
• Studies have biological plausibility and analogy to
clinical cases from drinking contaminated water
Epidemiological Studies of Recreational Water
Quality: Evidence Base
• Rate of certain symptoms or symptom groups were
significantly related to the count of fecal indicator
bacteria
• Consistency across various studies
• Gastrointestinal symptoms were the most frequent
health outcome for which significant dose-related
associations were reported
Health Effects Associated with Swimming
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•
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Gastrointestinal illness
Respiratory illness
Skin diseases
Ear, nose and throat
Probability of illness p/(1-p)
Swimming associated
Risk of illness in swimmers against bacterial counts in
marine water – A Prüss, (1998)
Bacterial count /100ml (geometric mean or median)
O
d
d
s
o
f
i
l
l
Case rate/1000
Swimming associated case rate /1000
Risks of illness in swimmers against bacterial count in
fresh water - A Prüss, (1998)
Bacterial count/100ml
Overall findings
• Swimmers have higher symptom rates than non-swimmers
• Fecal indicators (fecal streptococci and fecal coliforms/ E. coli)
associated with symptom rates
• Illness rate is associated with counts of fecal indicator ie, doserelated increase
• Overall, best indicators: fecal streptococci/enterococci for
marine waters; E. coli for freshwater
• Risk of gastrointestinal symptoms low at 30+ indicators/100 ml
Additional Observations
• Indicator:pathogen ratios vary according to health of
population
– Depends on types and magnitude of illnesses present
in study population at time of investigation
• Present indicators do not always provide good prediction
of epidemiological health risk
• Risk varies with:
– Immunity of population varies
• USA, UK, Egypt , Hong Kong and South Africa
• Local versus tourists
– Age groups – different severity and other responses
WHO Guidelines: Based on UK Studies - Judged Most Rigorous
WHO Guidelines: Based on UK Studies Judged Most Rigorous
The Upper 95% Percentile Approach
• Criteria for recreational water compliance is typically based on %
compliance levels. Either:
– 95% compliance levels (i.e., 95% of sample measurements lie
below a specific value in order to meet the standard) OR
– Geometric mean values
• Data are collected in the bathing zone
• Both criteria have significant drawbacks T
• Geometric mean is statistically more stable
– Because the inherent variability in the distribution of the water
quality data is not characterized in the geometric mean
– This is variability that produces the high values at the top end of the
statistical distribution that are of greatest public health concern
• 95% compliance reflects much of the top-end variability in the
distribution of water quality data and is more easily understood.
– affected by greater statistical uncertainty and so a less reliable
measure of water quality,
• thus requires careful application to regulation
Example of a Classification Matrix for Fecal
Pollution of Recreational Water Environments
Candidate
Fecal
Indicators:
Bacteria
Indicator
Advantages
Disadvantages
Fecal
Streptococci
/Enterococci
· Marine and fresh water human
health indicator.
· More persistent in water &
sediment than coliforms.
May not be valid for some waters,
due to potential growth in soils
and on vegetation.
Multiple species, not all of fecal
origin
· Confounded by non-sewage/nonfecal sources (e.g. Klebsiella spp.
in pulp and paper wastes)
Thermotolerant · Indicator of recent fecal
("fecal")
contamination.
coliforms
· Not suitable for some waters;
growth in soils and water
E. coli
· A fresh water human health
indicator.
· Indicator of recent fecal
contamination.
· Typing E. coli to track source
of fecal contamination.
· Rapid identification if based
on Beta-glucuronidase activity
Sulphite· Always in sewage impacted
reducing
waters.
clostridia /
· Possibly correlated with
Clostridium
enteric viruses and parasitic
perfringens
protozoa.
· Inexpensive assay with H2S
production for detection
· Sometimes not suitable for
tropical and some other waters
due to growth in soils and water.
- Poor survival in sea water; low
concentrations may give poor
predictability of health risks
· May be from animal feces, too
· Very conservative indicator; old
fecal contamination
· Enumeration requires anaerobic
culture or reduced medium
Somatic
coliphages
Candidate
Fecal
Indicators:
Viruses
and
Physical
Parameters
· Standard methods
· Similar behavior to human
enteric viruses
- Commonly present in feces and
sewage
F-specific
coliphages
· Standard methods
· More persistent than some other
coliphages
· Host does not grow in
environmental waters below 30°C
- Potential use for microbial
source tracking
Bacteroides · May be sewage-specific in some
fragilis
regions
phages
· Methods available; molecular
better than cuilture methods
· More resistant than most other
phages in the environment; similar
to human enteric viruses
Sanitary
· Immediate assessment possible
plastics
each bathing day.
· Can be categorized
· Need Little staff training
Preceeding
rainfall
(12, 24, 48
or 72 hours)
· Simple regressions may account
for 30-60% of variability in
microbial indicators for particular
beaches
· Sewage specificity uncertain
· Heterogeneous; different groups
Persistence of some may differ from
human enteric viruses
· May grow in some environments
(uncertain)
· Present in sewage but not always
in feces of individuals
- Specific to sewage
· Some are not as persistent in
marine or warm waters as some
enteric viruses
· Need anaerobic culture.
· Numbers in sewage are lower than
other phages; most humans do not
excrete (hence no value for small
populations
- Must use molecular detection
· May reflect old sewage
contamination and be of little health
significance
· Subjective and prone to variable
description.
· Each beach area may need to
assess its rainfall response/risk
· Response may depend on
conditions before an event
Candidate Fecal Indicators – Chemical and Physical
Fecal
sterols
· Coprostanol is sewage-specific
· Coprostanol degradation similar to die-off of
thermotolerant coliforms
· Ratio of 5b/5a stanols > 0.5 is indicative of faecal
contamination. i.e. coprostanol/5a-cholestanol >
0.5 indicates human fecal
contamination; while C29 5b (24 ethylcoprostanol)
/ 5a stanol ratio >0.5 indicates herbivore feces.
· Ratio of coprostanol:24-ethylcoprostanol can be
used to indicate the proportion of human fecal
contamination
Caffeine
· May be sewage-specific, but unproven
· Could be developed into a dip-stick assay.
Detergents · Relatively routine methods available.
Turbidity
· Requires gas
chromatographic
analysis and is expensive
(about
$100/sample).
· Requires up to 10 L of
sample to be filtered
through a glass fibre filter
(Whatman) to concentrate
particulate stanols
· Yet to be proven as a
reliable method
· May not be related to
sewage (e.g. industrial
pollution)
· Simple, direct and inexpensive assay available in · May not be related to
the field.
sewage; correlation
needed for each site type
Many Chemical Indicators are
Available to Detect in Water
•
•
•
•
•
Optical brighteners
Fecal sterols
Caffeine
Antibiotic residues
Other pharmaceuticals and personal care products
– analgesics and anti-inflammatories
– lipid regulators
– antiepileptics
– beta blockers (antihypertensives)
Some Problems with Current Bacteria Indicators: Misclassification
of Fecal Contamination and Human Health Risks
• E. coli and enterococci not always from fecal contamination
• E. coli proliferates in the environment at some conditions
Enterococci not specific to fecal contamination or to only
human fecal contamination
– Approved medium detects many enterococci, not just E.
faecium and E. faecalis;
– Animal and environmental enterococci are detected
– Some states use alternative media having unknown or poorly
characterized performance to detect enterococci
• E. coli and enterococci are inadequate predictors of viral and
possibly parasite risks from waterborne exposures
• No proven microbial indicators for viruses and parasites
US EPA Recreational Water Quality Criteria Freshwater
• From a statistically sufficient number of samples (generally
5+ samples equally spaced over a 30-day period)
• Geometric mean bacterial densities not to exceed either:
– E. coli 126/100 ml; or
– enterococci 33/100 ml;
• no sample should exceed a one-sided confidence limit (C.L.)
calculated using the following as guidance:
–
–
–
–
–
designated bathing beach 75% C.L.
moderate use for bathing 82% C.L
light use for bathing 90% C.L.
infrequent use for bathing 95% C.L.
based on a site-specific log standard deviation, or if site data are
insufficient to establish a log standard deviation, then using 0.4 as
the log standard deviation for both indicators.
US EPA Recreational Water Quality Criteria Marine Water
• From a statistically sufficient number of samples (generally 5+
samples equally spaced over a 30-day period)
• geom. mean enterococci densities not to exceed 35/100 ml;
• no sample exceed a one-sided CL using the following guidance:
– designated bathing beach 75% C.L.
– moderate use for bathing 82% C.L.
– light use for bathing 90% C. L.
– infrequent use for bathing 95% C. L.
– based on a site-specific log standard deviation, or if site
data are insufficient to establish a log standard deviation,
then using 0.7 as the log standard deviation.
US EPA CRITERIA FOR INDICATOR
BACTERIOLOGICAL DENSITIES
EPA BEACHES Program
http://www.epa.gov/OST/beaches
• Congress passed legislation in 2000 to address the need for
improved protection of public health at beaches
• Beaches Environmental Assessment and Coastal Health (BEACH)
Act.
• Stronger beach monitoring programs
• EPA to work partnership with state and local governments
• Must make significant progress in improving public health at our
nation’s beaches
• Issues about the situation in some states and territories
– Still relying on the 1968 200 FC/100 mL water standard as their primary
indicator for recreational waters
– Fecal and/or total coliform standards more stringent than the US PHS 200 FC/
100 mL and/or 1000 TC/100 mL
– Provisions in which the numeric criteria for bacteria standards do not apply
where CSOs and storm water discharges are likely to result in violations
Progress in Implementing the
BEACHES Act
Progress in Implementing the BEACHES Act, Cont’d.
Progress in Implementing the BEACHES Act, Cont’d.
New Zealand Recreational Water Quality Guidelines
New Zealand Recreational Water Quality Guidelines
Issues for Current Management: Classification of Fecal
Contamination and Human Health Risks by USA vs. WHO
• USA beaches are classified as safe or unsafe:
– OK to swim or no swimming
• Actually, there is a gradient of increasing risk
– Increased severity, variety and frequency of health
effects with increasing sewage/fecal pollution
• Desirable to promote incremental improvements by
identifying and prioritizing ‘worst failures’ to move towards
an improved category of water quality
• WHO approach of risk gradations based on sanitary
conditions and water quality, with communication of risks, is
more rational
– Recognizes differences in local and regional conditions and
encourages incremental improvement
Current Recreational Water Quality Management - Problems
• Management actions (e.g., beach closures/postings) are
retrospective
– Occur only AFTER human exposure to the hazard
– It takes too long to get test results
• Risks to health are primarily from human and secondarily
from animal excreta
– But, traditional bacterial indicators may also derive from other
non-fecal sources (vegetation, soil, etc.)
• Poor inter-laboratory and international comparability of
microbiological analytical data
• Climate and geographic differences are a challenge in setting
universal criteria and standards
– Temperature and water quality differs, as does disease burdens