Microbial Contamination of Recreational Waters

Colin I. Mayfield

Professor of Biology, University of Waterloo and Assistant Director, United Nations University -

International Network for Water, Environment and Health

Recreational waters refer to those natural waters used not only for primary contact activities, such as swimming, windsurfing, and waterskiing, but also for secondary contact activities, such as boating and fishing.

Recreational use is defined as any activity involving the intentional immersion (e.g., swimming) or incidental immersion (e.g., waterskiing) of the body, including the head, in natural waters.

Natural water is defined as any marine, estuarine or fresh body of water, as well as any artificially constructed flow-through impoundment using untreated natural waters.

The total global health impact of human infectious diseases associated with pathogenic micro-organisms from land-based wastewater pollution of coastal areas has been estimated at about three million disability-adjusted life years (DALYs) per year, with an estimated economic loss of around 12 billion dollars per year (Shuval 2003).

Researchers in the United States have estimated that the health burden of swimming-related illnesses at two popular beaches in California, USA exceeds US $3.3 million per year.

The annual costs for each type of swimming-related illness at the two beaches were estimated to be: gastrointestinal illnesses, US $1,345,339; acute respiratory disease, US $951,378; ear complaints, US $767,221; eye complaints, US $304,335 (Dwight et al. 2005).

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Economic Costs

Topics

• Microbial contamination

• Sources of contamination

• Beach contamination

• Populations at higher risk

• Developments in analytical technologies and control measures

• Overview

• Extra - Emerging Pathogens

Microbial Contamination

The Great Lakes Water Quality Agreement states that:

“recreational waters should be substantially free from bacteria, fungus and viruses that may produce enteric disorders or ear eye, nose, throat and skin infections or other human diseases and disorders”

The primary tool used at present to evaluate water quality is the measurement of indicator organisms that estimate the level of faecal contamination of the water

The primary organisms used are faecal coliforms, Escherichia coli and enterococci.

They are considered indicative of faecal contamination and possible presence of intestinal-disease-causing organisms

Microbial Contamination

Standards vary, but many jurisdictions close beaches when E. coli levels reach 100 organisms per 100 mL

Other jurisdictions use 200 per 100 mL of faecal coliforms as the criterion.

The European Union is moving to a system that rates beaches as “good” (the minimum acceptable level) and “excellent” based on E. coli ( 250 And 500 cfu/100mL) and enterococci counts (100 and 200 cfu/100mL). Other categories are “sufficient” and “poor”

Is there evidence that increased levels of these indicators leads to increases in infection?

95th percentile of IE/100 mL

10%

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Risk of contracting Gastroenteritis and Respiratory illness (Acute Febrile Respiratory Illness) at different Intestinal Enterococci levels

0 50 100 150 200 250 300 350 400 450 500

AFRI

GI

European Union Directive 2002/0254

The ratio of Escherichia coli to Enterococci found in those studies to reflect equal risk was between 2 and 3

The European Union therefore developed the following standards for“bathing waters”:

Parameter Excellent Quality Good Quality

Intestinal enterococciIn cfu/100 mL 100 200

Escherichia coli incfu/100 mL 250 500

Monitoring frequency was made flexible to allow for waters with few contamination occurrences

Sources of Contamination

WHO

Many sources contribute to microbiological contamination, including:

combined or sanitary sewer overflows (CSOs and SSOs), unsewered residential and commercial areas, and failing private, household and commercial septic systems.

Other sources may be:

agricultural runoff (such as manure fecal coliforms from animal/pet fecal waste washed from soil

by heavy rains, either from the beach or washed into residential storm sewers

wildlife waste, as from large populations of gulls or geese fouling the beach

direct human contact, such as swimmers with illnesses, cuts or sores; or high numbers of swimmers/bathers in the water, which are related to increased bacterial levels

direct discharges, for example from holding tanks of recreational vessels.

Other factors affecting contamination levels are:

low (shallow) water levels hot weather and higher temperatures high winds that can cause increased wave action that can

transport bacteria from contaminated, non-recreational areas to recreational-use areas

high winds that can stir up bacteria that are in the sediments

calmer waters that can slow dispersal and create excess concentrations of bacteria.

Other Sources

Beach sand and mats of algae floating along shorelines both harbour E. coli for long periods.

E. coli can even survive over winter in beach sand.

Bacteria sheltered in sand or algae can repopulate shoreline water with such high concentrations that beaches are closed even when there are no obvious new sources. Such sources would include sewer overflows or heavy rains that either flush contaminants out of storm sewers or wash bird droppings off nearby parking lots.

Whitman (USGS).

Other Sources

As Lake Michigan's water level has receded to near-record low levels in the last year, beaches have become wider and attracted more waterfowl, particularly gulls. Gull faeces is loaded with E. coli. "You would need 1,000 geese to match the E. coli burden from a single gull," (Sandra McLellan, an assistant scientist at the Great Lakes WATER Institute in Milwaukee)

As beach areas increase, there are higher average concentrations of E. coli. At one site, North Point Marina, the beach increased in size by 255% between 1997 and 2000 while average E. coli concentrations rose 391%.

Mark Pfister, an aquatic biologist with the Lake County Health Department in Waukegan, consistently found the highest concentrations of E. coli at Waukegan South Beach where there were no storm or sanitary sewers discharging close to it, but it did have the greatest number of gulls among beaches in the county.

Canadian Guidelines for Recreational Water

Waters used for recreational purposes should be sufficiently free frommicrobiological, physical, and chemical hazards to ensure that there is negligible risk to the health and safety of the user. The determination of the risk of disease or harm from microbiological, physical, or chemical hazards is based on a number of factors, including the following:

Environmental health assessments

Epidemiological evidence

Indicator organism limits

Presence of pathogens.

The decision to post a warning to users of recreational areas or to close an area for public use should be made by the Medical Health Officer or other appropriate authority in accordance with the statutes existing in each province.

This decision will be based on an assessment of existing hazards usingavailable information on the factors listed above.

Environmental Health Assessments

An annual environmental health assessment should be carried out prior tothe bathing season on the watershed or the area from which water flows to a recreational area, as well as on the recreational area itself. This survey should identify all potential sources of contamination and physical hazards that could affect the recreational area.

Attention should be paid to the following:

the risk of inadequately treated sewage, fecal matter, or chemical substances entering the water, from either a discharge or a spill

knowledge of all outfalls or drainage in the area that may contain sewage, including urban storm water and agricultural waste or runoff

an inspection of the area for physical hazards

an assessment of the seasonal variability of hazards, the density of bathers, the water temperature, the frequency of change or circulation of the water, changes in water depth, and the occurrence of algal blooms

the fluctuation of water quality with rainfall (wet and dry conditions)

a reporting mechanism to ensure that health authorities are informed of any malfunction or change to a municipal, private, or industrial waste treatment facility that might cause a deterioration of the water quality of

Epidemiological Evidence

The local health authorities responsible for making recommendations fora recreational area should, wherever possible, establish surveillance for bather illness or injuries.

This can be established by comprehensive epidemiological studies or by formal and informal reporting from physicians and hospital emergency departments. This surveillance will be increased if there have been reports of suspected illness or injuries. The water quality may be considered impaired and appropriate recommendations made as a result of this surveillance.

Presence of Pathogens

Tests for pathogenic organisms may be carried out when there have beenreports of illnesses of specific etiology, when there is suspected illness of undetermined cause, or when levels of an indicator organism demonstrate a continuous suspected hazard. The tests will help to determine the source of contamination (e.g., sewage pollution, agricultural or urban runoff, bather origin).

The local health authorities should take action when pathogenic organisms are identified in sufficient quantity or frequency to be considered a hazard.

An appropriate response should be based on the knowledge of the source of the organism and the probability of the hazard being temporary or continuous.

Indicator Organisms

The best indicators of the presence of enteric pathogens in fecal pollution sources should have the following properties

present in fecal-contaminated waters when enteric pathogens are present but in greater numbers

incapable of growth in the aquatic environment but capable of surviving longer than pathogens

equally or more resistant to disinfection than pathogens

easily and accurately enumerated

applicable to all types of natural recreational waters (e.g., fresh, estuarine, and marine)

absent from non-polluted waters and exclusively associated with animal and human fecal wastes

density of indicator should be directly correlated with the degree of fecal contamination

density of indicator should be quantitatively related to swimming associated illnesses.

(National Academy of Sciences 1977; Cabelli et al. 1983; Elliot and Colwell 1985):

Indicator Organism

An indicator organism or organisms should be chosen by the local healthauthority in consultation with the laboratory microbiologists for each area.

It is recommended that one of the following indicator organisms be used for routine monitoring of recreational water quality – enterococci, Escherichia coli, or fecal coliforms.

May change based on Ontario’s new regulations for drinking water ?

The choice of indicator organism and of enumeration procedures will bedetermined according to:

whether the water is marine (salt), fresh, or estuarine (variable salinity)

the presence of turbidity, which may interfere with microbiological methods

any known correlation of illness with levels of indicator organisms

the proportion of fecal coliforms in the area that are E. coli, if fecal coliforms are used as indicator organisms

local experience of monitoring with a particular organism.

The decision to carry out routine microbiological monitoring of a recreational area will be made by the local health authorities or other responsible agency, based on the usage of the area, the environmental health assessment, and epidemiological evidence.

Presence of Pathogens

Tests for pathogenic organisms may be carried out when there have been reports of illnesses of specific etiology, when there is suspected illness of undetermined cause, or when levels of an indicator organism demonstrate a continuous suspected hazard.

The tests will help to determine the source of contamination (e.g., sewage pollution, agricultural or urban runoff, bather origin).

The local health authorities should take action when pathogenic organisms are identified in sufficient quantity or frequency to be considered a hazard.

Modelling methods can be used to assist in management of recreational waters

The overall objective of all beach advisory predictive tools is to reduce the risk of illness due to exposure to elevated levels of pathogens. The tools currently in use by responsible agencies vary in their complexity and approach to minimizing exposure.

Rainfall Analysis In the City of Milwaukee, City of Stamford, and the Delaware

Department of Natural Resources and Environmental Control (DNREC), regression analysis relates rainfall to pathogen concentration. Models developed based on this approach are site-specific since they are derived from locally observed relationships between water quality and rainfall data.

Simulation of water quality conditions Models can be used under a variety of scenarios of untreated or

partially treated wastewater. Comparison of the resulting water quality conditions to the established action level, such as the water quality standard, can serve as the basis for the beach advisory or closure.

Beach Contamination

Major findings on spatial variation are:

In every case, the zone from which the sample was collected was found to have the greatest predictable impact on microbial indicator densities of all factors investigated in this study, spatial or temporal. Bacterial densities become progressively lower as one moves from ankledeep to knee-deep to chest-deep water.

Two of the study beaches, Belle Isle and Miami Beach Park, exhibited some form of systematic spatial variation that was not adequately accounted for by zones alone. It may or may not be a coincidence that both of these beaches are associated with river systems.

Summary of Factors (correlates) of microbial indicators in recreational waters (from the EMPACT study)

Spatial Factors – lower levels in deeper waters (away from shore)

Temporal Factors – lower levels in the afternoon than the morning (often lower on sunny days than on overcast days)

Temporal factors – Faecal indicator levels varied significantly from day to day – only limited statistical relationship between sampling on one day and the next day’s samples

Environmental factors –

Substantial rainfall increased levels

Onshore winds increased levels

Bather density did not give consistent effects

In a study of a beach on Lake Michigan, beach sand:

Played a major role in bacterial lake water quality

Was an important source of indicator bacteria to the water rather than a net sink

May be environmentally, and perhaps hygienically, problematic

Was possibly capable of supporting an autochthonous, high density of indicator bacteria for sustained periods, independent of lake, human, or animal input

Richard L. Whitman and Meredith B. Nevers “Foreshore Sand as a Source of Escherichia coli in Nearshore Water of a Lake Michigan Beach” Applied and Environmental Microbiology, September 2003, p. 5555-5562

In other studies, groundwater movement through the sand on beaches was shown to cause release of microorganisms into the water.

The groundwater itself did not have elevated levels of the indicator bacteria and was thought to “free” bacteria that otherwise would remain in the beach sediments

(Boehm and Paytan, Stanford University)

This may account for some increases in indicator bacteria that occur near beaches where there is no known point or non-point source.

Populations at higher risk

Diseases that are normally mild and self-limiting in the general population can have severe manifestations in susceptible sub-populations with certain attributes. A variety of host factors impact susceptibility to severe disease outcomes.

Human immune status can be affected by diseases (HIV, cancer), age, medications taken (e.g., chemotherapy treatment of cancer weakens the immune system), pregnancy, nutritional status, genetics and other factors (Carr and Bartram 2004).

The population of immunocompromised individuals is growing (Soldatou and Davies 2003). This population is more susceptible to waterborne infections and tend to experience more severe outcomes (e.g., debilitating illness, death) following infection (Reynolds 2003).

The table shows the case-fatality observed for enteric pathogens in nursing home patients in the USA who are more susceptible to infection compared with the general population.

Higher risks for children from recreational use of water

Children are at higher risk because of:

Lower immune functions

Greater ingestion of water and beach sand

Longer exposure times to water and beach sand

Greater use of “water park” equipment such as swimming pools, fountains, sprays, wading pools, etc that may be deficient in chlorination

OverviewUntil new technologies for detection and analysis are developed and proven, the use of E. coli, faecal coliforms and enterococci as “indicator organisms” for faecal contamination of recreational waters will continue

A significant improvement would be the use of genetic analysis to determine the animal source of the indicator organisms

Beach sand could be a significant reservoir of indicator organisms (and pathogens) that are released into the water

There is a significant (and increasing) proportion of the population that has decreased immune function and they could be at higher risk for contacting disease from recreational waters.