Transcript Recreational Use of Water

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.
Economic Costs
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).
.
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?
Risk of contracting Gastroenteritis and Respiratory illness (Acute
Febrile Respiratory Illness) at different Intestinal Enterococci levels
10%
GI
9
8
7
6
5
AFRI
4
3
2
1
0%
0
50 100 150 200 250 300 350
95th percentile of IE/100 mL
European Union Directive 2002/0254
400 450
500
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 enterococci
In cfu/100 mL
100
200
Escherichia coli in
cfu/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 from
microbiological, 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 using
available information on the factors listed above.
Environmental Health Assessments
An annual environmental health assessment should be carried out prior to
the 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 for
a 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 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.
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 health
authority 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 be
determined 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 sitespecific 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 subpopulations 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
Overview
Until 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.