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State-of-the-Science: Fecal Source Identification and Associated Risk Assessment Tools


Background

Development of fecal source identification tools has provided new opportunities for improved beach management, including the ability to prioritize beaches having the greatest health risk based on known differences in pathogenicity among fecal sources. Fecal source identification abilities have also spurred development of new risk evaluation tools, such as quantitative microbial risk assessment (QMRA) and natural source exclusion (NSE), that are becoming part of the regulatory framework. However, the field of source identification is still evolving rapidly and the associated evaluation tools are in their infancy.

Objectives

This workshop aimed to summarize and encourage audience discussion about the state of knowledge regarding the following questions:

  1. How accurate are present techniques for determining whether the fecal signature at a beach is human or non-human in origin?
  2. What are the relative health risks between human and non-human fecal sources?
  3. What is the level of scientific uncertainty when using this information in a management context?

The workshop also sought to identify the research most needed to enhance the scientific foundation for each of these questions.

Dates

This workshop was held at SCCWRP in Costa Mesa, California November 28-29, 2012.

Summary

Managers and experts from around the country were invited to attend four sessions over the course of two days. The first two sessions addressed the scientific foundation for determining and interpreting sources of fecal contamination. The second set of sessions addressed scientific uncertainties associated with potential evaluation at beaches with non-human sources. Half the time in each session was allocated to hearing presentations by national experts, who provided the latest scientific information on the topic. This was followed by a panel discussion in which the experts addressed a set of predefined questions, as well as those provided by the audience. The workshop agenda lists the specific panel questions and expert panel members. The meeting summary describes a few main observations:

• There was widespread recognition that the field of source identification is still evolving rapidly and that associated evaluation tools are in their infancy. There will be many new and novel advances in the field of source tracking over the next several years.

• Experts from the US Environmental Protection Agency explained how fecal source identification abilities have spurred development of new risk evaluation tools such as quantitative microbial risk assessment (QMRA) and natural source exclusion (NSE), which are becoming part of the regulatory framework.

• Questions about using QMRA and NSE indicated that much research is still needed before these risk assessment tools can be fully utilized. Major knowledge gaps include pathogenicity of microorganisms, especially from non-human hosts, and survival and detection of appropriate pathogens under different environmental conditions over time.

• Lastly, much discussion indicated that there is great need for a research study to address the persistence and degradation of source-associated markers from various hosts and fecal indicator bacteria over time in different matrices under a wide range of environmental conditions.

Presentations


Date Presentations
November 28
Session 1:
Current prospects for detecting human sources of fecal pollution
Differentiating between human and non-human sources using source-associated markers
Human indicator persistence in the environment
Uncertainty issues relating to detection of human indicators

Session 2:
Characterization of pathogens in non-human fecal matter
Waterborne pathogens from non-human sources and their public health implications
Current status on quantifying sources of microbial contamination
Uncertainty issues relating to detection of non-human indicators

November 29
Session 3:
Overview of QMRA
QMRA case study
QMRA case study: Kiddie Beach
Uncertainty issues relating to application of QMRA

Session 4:
The conceptual basis for natural source exclusion
Natural source exclusion case study: Reedy Creek, Florida
Hawaii's use of Clostridium: A form of natural source exclusion?
Is Santa Monica Pier a form of natural source exclusion?


Sponsors

This workshop was organized by SCCWRP on behalf of the California Beach Water Quality Work Group and California Clean Beach Task Force, and supported by Geosyntec Consultants and the City of Dana Point.