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Rethinking Recreational Water Monitoring: Can Predictive Modelling Increase Public Health Outcomes?. Dr. Andrew Papadopoulos Associate Professor and Coordinator, Master of Public Health Department of Population Medicine University of Guelph, Ontario, Canada

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rethinking recreational water monitoring can predictive modelling increase public health outcomes

Rethinking Recreational Water Monitoring: Can Predictive Modelling Increase Public Health Outcomes?

Dr. Andrew Papadopoulos

Associate Professor and Coordinator, Master of Public HealthDepartment of Population MedicineUniversity of Guelph, Ontario, Canada

NEHA Annual Educational Conference and IFEH World Congress

July 8, 2014

  • The public health issue
  • The current regulatory state In Ontario, Canada
  • The use of E. coli as a measurement tool
  • Geometric means
  • Predictive modeling
  • Risk communication
  • A multi-barrier approach
  • Increasing public health outcomes
  • Moving forward
  • Pathogenic microorganisms such as Shigella, enterohaemorrhagicEscherichia coli (EHEC), Giardia, Cryptosporidium, Norovirus, and Leptospira have been linked to disease outbreaks from exposure to recreational waters in North America
  • Gastrointestinal illness is the most well-studied outcome associated with recreational water quality, but febrile respiratory illness and ear and skin infections are also of concern
potential burden of illness
Potential Burden of Illness
  • According to Ontario Parks, approximately 9 to10 million persons use their parks per year
  • Wasaga Beach – estimated 2 million visitors annually
the issue
The Issue
  • Timeliness of E. coli test
  • Varying standard of number of E. coli per 100mL of recreational water
  • There is a lack of supporting epidemiological evidence that supports the current standard or any other standard
  • Is current method most effective, both in terms of scarce resource consumption and public health?
current ontario ministry of health program
Current Ontario Ministry of Health Program

The goal of the Safe Water Program Standard

  • Prevent or reduce the burden of water-borne illness and injury related to recreational water use
  • Boards of health are required to manage service delivery to their recreational facilities and water front activities program in accordance with the protocols under this standard
  • Must undertake assessment and surveillance, develop policies and health promotion strategies, prevent disease, and protect human health
ophs beach management and recreational water protocols
OPHS: Beach Management and Recreational Water Protocols

Under the protocols, boards of health have the following reporting requirements

  • Provide Safe Water Program common data elements
  • Conduct surveillance of public beaches and recreational water facilities
  • Conduct surveillance of water-related illnesses
ophs beach management and recreational water protocols1
OPHS: Beach Management and Recreational Water Protocols
  • Provide education for owners and operators
  • Implement a recreational water management program to reduce risks of illness or injury from recreational activities
  • Provide 24/7 on-call response for issues relating to recreational water activities
ophs beach management and recreational water protocols2
OPHS: Beach Management and Recreational Water Protocols

Surveillance and Inspection

  • Pre-season assessment
    • Inventory of public beaches
    • Historical and epidemiological data
    • Environmental survey
  • Routine public beach surveillance
    • Sampling program (as per water sampling methodology)
      • Special consideration for frequency and timing of sampling and items as noted above
ophs population health assessment and surveillance protocol
OPHS: Population Health Assessment and Surveillance Protocol

Under the protocol, boards of health have the following reporting requirements

  • BOH must conduct surveillance of water-related illnesses associated with recreational activities
  • Conduct epidemiological analysis of surveillance data, monitor trends (spatial and temporal), and vulnerable populations
use of fecal indicator bacteria
Use of Fecal Indicator Bacteria
  • Health Canada distinguishes between three types of fecal indicators
    • Primary fecal indicators inform on the level or the extent of fecal contamination
    • Secondary fecal indicators provide clues to the sources of contamination, for example distinguishing between human and cattle fecal material
    • Pathogen indicators are intended to help estimate the risk from a specific pathogen
  • There is no single perfect fecal indicator
use of fecal indicator bacteria1
Use of Fecal Indicator Bacteria
  • An indicator should survive longer than pathogens; however, guidelines point out that, “The density of the indicator should be quantitatively related to swimmer-associated illnesses”
    • Unlikely in cases of intermittent contamination when the indicator persists in the environment for longer than the pathogen
    • Turbidity can interfere with the quantification of indicator organisms by allowing multiple bacteria to adhere to a single particle and therefore, create a single colony in assay, and also by interfering with membranes used in filtration
use of fecal indicator bacteria2
Use of Fecal Indicator Bacteria
  • Current practice emphasizes using information about primary fecal indicators to estimate the level of risk to recreational water users
  • Two types of bacteria are used as primary fecal indicators: Escherichia coli (fresh water) and enterococci species (marine water)
  • Meta-analysis of epidemiological data on swimming-associate gastroenteritis supported the use these organisms
testing standards canada
Testing Standards: Canada


  • 35 BOHs use 100 E. coli limit
  • Canada’s guideline value of 200

Other Provinces

  • Use the 200/400 E. coli/100 ml value; with variations
  • Some allow for use of thermo-tolerant coliforms
  • Quebec uses water quality grades (A-D) below 200
trigger for action
Trigger for Action

Currently Ontario’s boards of health use 100 E.coli per 100 mL (based on a geometric mean of at least 5 samples) as a trigger value for action

geometric mean
Geometric Mean
  • The geometric mean is calculated by converting the counts from a minimum of five or six samples to a logarithmic scale, calculating the mean, and converting that mean value back to a base 10 number
  • The relationship between fecal indicators and illness is on a log scale, so the use of a geometric mean is appropriate
daily geometric mean and the persistence model
Daily Geometric Mean and the Persistence Model
  • Results from cultures can take 18-24 hours
  • Therefore, beach management decisions based on a previous day’s cultures have been termed a “persistence” model
  • The temporal variability in indicators coupled with the delay in obtaining culture results often means that beaches are still open at times of peak risk, and closed later, once risk has already begun to fall
monthly and seasonal geometric means
Monthly and Seasonal Geometric Means
  • Weekly sampling can be appropriate to identify new, but persistent contamination problems
  • Can be used to estimate risk with samples taken at different times within a defined period
  • Many regions in Canada and the US use a geometric mean of samples taken over the preceding month as the basis for beach management decisions
various guideline values
Various Guideline Values
  • A guidelines of ≤200 E. coli per 100 mL for freshwater has a risk of 10 per 1000 bathers, while 100 E. coli per 100 mL has a risk of 4.5 per 1000 bathers
  • Some guidelines have a ceiling value of ≤400 E. coli per 100 mL which has shown to discourage more extensive or targeted sampling because such practices are more likely to generate a sample above the ceiling
  • An alternative approach specifies that the geometric mean (of at least six samples) may not exceed 200 E. coli per 100 mL and a statistical threshold value of 400 E. coli per 100 mL that cannot be exceeded by more than 10% of samples
spatial consideration in sampling
Spatial Consideration in Sampling
  • A US EPA (2005) study at five beaches found that sample depth was the strongest predictor of indicator levels
    • Levels decreased significantly and progressively from ankle depth, to knee depth, to chest depth
  • Sampling where water reaches a depth of 1.2-1.5 m (equivalent to adult chest level) best predicts swimming-associated illness
  • Health Canada suggests sampling from non-representative sites where contamination has the potential to be higher, such as areas under direct influence of storm water, sewage, or river outlets
    • Can be valuable for understanding the sources of contamination in an area
temporal considerations in sampling
Temporal Considerations in Sampling
  • A study by the US EPA (2005) found that at three of the five beaches studied, levels tended to decline from the early morning to the afternoon
  • Also found that at least half of the time, the daily geometric mean changed by at least a factor of two from one day to the next
  • “When sampling, consideration should also be given to the collection of samples for the purposes of characterizing event-driven episodes of pollution that may affect recreational waters – for example, immediately following periods of heavy rainfall or at times of greatest swimmer activity.”
predictive modeling
Predictive Modeling
  • A means of getting timely estimates of fecal contamination through the use of readily available environmental explanatory variables to “predict” the levels of fecal indicator organisms that would be cultured from water samples taken in the present
  • Predictive models have focused on modeling fecal indicator bacteria as the best available surrogate for human health risk
  • The ideal model would estimate infection risks not only from fecal bacteria, but a full range of pathogens
risk communication
Risk Communication
  • A method of reducing exposure when water quality hazards are present
    • Posting warning signs is an accepted means of communicating that a beach is temporarily unsuitable for swimming
  • Three elements must be present
    • Identification of health or safety risk
    • A recommended action to take
    • The name and contact info for the authority responsible the warning
  • Some jurisdictions are incorporating international icons for safe or unsafe swimming into any warning signs
evidence gaps
Evidence Gaps
  • Understanding of the risk factors for swimming-related infections
  • In Canada, there is the added challenge of limited domestic surveillance
  • Lack of surveillance for illnesses related to recreational water use in order to improve risk assessments
risk management framework applying a multi barrier program
Risk Management Framework: Applying A Multi-barrier Program
  • The WHO (2003) also endorses a multi-barrier approach where ideally, water quality hazards are identified and addressed before recreational water users are ever exposed
risk management framework applying a multi barrier program1
Risk Management Framework: Applying A Multi-barrier Program

Components of a risk management framework

  • Environmental (sanitary) survey
    • Wave conditions
    • Land use activities
    • Number of bathers
    • Animal/bird activities
  • Inspection and assessment
    • Risk-based assessment approach
    • Predictive models
risk management framework applying a multi barrier program2
Risk Management Framework: Applying A Multi-barrier Program

Surveillance and monitoring initiatives

  • Sampling program
  • Epidemiological data

Laboratory testing and diagnostic services

  • Laboratory turnaround time = 24 hours to report indicator results
risk management framework applying a multi barrier program3
Risk Management Framework: Applying A Multi-barrier Program

Public Communication and Notification

  • Develop risk communication plan


  • Conduct an evaluation of program
increasing public health outcomes
Increasing Public Health Outcomes

Using predictive modeling to establish a risk management framework

  • It is recognized that relying solely on E. coli results may not reflect the current state of the recreational water
  • Each public health agency must complete the pre-season assessment
  • Framed in an epidemiological study, the outcome of interest is water quality where the independent variables would be items such as surrounding land use, meteorological events, natural landscape, algae growth, and turbidity
  • The establishment of such a framework could potentially reduce the amount of sampling required thereby reducing costs and provide timelier advice to the public
increasing public health outcomes1
Increasing Public Health Outcomes

Validate the current threshold for action

  • Different jurisdictions use different standards and different sampling techniques 
  • Sufficient research into the appropriate action levels should be available before changing procedures and a two to five year epidemiological study to establish the most appropriate bacterial threshold level would be helpful in both quantifying the amount of illness and the potential level of illness to the public
increasing public health outcomes2
Increasing Public Health Outcomes

Develop a robust communication plan that is well understood by partners and stakeholders, including the public and the media

  • The exploration of a standard sign that is well understood by the residents and visitors would be helpful in conveying the potential level of risk
  • The employment of risk communication experts would be valuable to ensure the message is clear and understandable
moving forward
Moving Forward
  • Research is required to create an evidence-based recreational water use program that can be communicated and shared with partners and stakeholders
  • The establishment of a risk management framework that could aid BOHs in a predictive model capacity is required
moving forward1
Moving Forward
  • It is of paramount importance to analyze the current threshold for action of 100 E. coli per 100 ml
  • A robust communication plan that is well understood by partners and stakeholders, including the public and the media must be developed
  • The National Collaborating Centre for Environmental Health
  • The Ontario Ministry of Health and Long-term Care
  • Dr. Justine Hutchinson
thank you
Thank you...

Questions or Comments?

Andrew Papadopoulos