Download
recreational water quality and health n.
Skip this Video
Loading SlideShow in 5 Seconds..
Recreational Water Quality and Health PowerPoint Presentation
Download Presentation
Recreational Water Quality and Health

Recreational Water Quality and Health

277 Vues Download Presentation
Télécharger la présentation

Recreational Water Quality and Health

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Recreational Water Quality and Health ENVR 890 Mark D. Sobsey Spring, 2007

  2. 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

  3. Health Risks from Recreational Water • Drownings • Spinal and other related “sports” injuries • Diving • Falling (slipping) • Boating accidents • Chemical exposures

  4. 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.

  5. Simplified Framework and Decision Tree for Recreational Water Management

  6. 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)

  7. WHO Guideline Values For Microbial Quality of Recreational Waters

  8. 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

  9. 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

  10. Health Effects Associated with Swimming • Gastrointestinal illness • Respiratory illness • Skin diseases • Ear, nose and throat

  11. Risk of illness in swimmers against bacterial counts in marine water – A Prüss, (1998) Probability of illness p/(1-p) Swimming associated Case rate /1000 Swimming associated Bacterial count /100ml (geometric mean or median)

  12. Risks of illness in swimmers against bacterial count in fresh water - A Prüss, (1998) Case rate/1000 Swimming associated case rate /1000 Probability of illness, p/(1-p) Swimming associated case rate/1000 Odds of ill Bacterial count/100ml

  13. 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, dose-related increase • Overall, best indicators: fecal streptococci/enterococci for marine waters; E. coli for freshwater • Risk of gastrointestinal symptoms low at 30+ indicators/100 ml

  14. 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

  15. WHO Guidelines: Based on UK Studies - Judged Most Rigorous

  16. WHO Guidelines: Based on UK Studies - Judged Most Rigorous

  17. 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

  18. Example of a Classification Matrix for Fecal Pollution of Recreational Water Environments

  19. Candidate Fecal Indicators: Bacteria

  20. Candidate Fecal Indicators: Viruses and Physical Parameters

  21. Candidate Fecal Indicators – Chemical and Physical

  22. 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)

  23. 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

  24. 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.

  25. 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.

  26. US EPA CRITERIA FOR INDICATOR BACTERIOLOGICAL DENSITIES

  27. 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

  28. Progress in Implementing the BEACHES Act

  29. Progress in Implementing the BEACHES Act, Cont’d.

  30. Progress in Implementing the BEACHES Act, Cont’d.

  31. New Zealand Recreational Water Quality Guidelines

  32. New Zealand Recreational Water Quality Guidelines

  33. 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

  34. 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