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ENVR Seminar: Wet Weather and Bacteria: Does Swimming in Stormwater Actually Make You Sick?” Ken Schiff, Deputy Director

Date: Thursday, October 26

Time: 3:40 pm - 4:55 pm

Location: 410 John D. Tickle Building

Current recreational water quality standards for fecal indicator bacteria (FIB) are based almost exclusively on swimmer epidemiology studies focused on human sources of fecal pollution during dry weather. Nationally, however, the majority of water quality criteria exceedances – and subsequent enforcement actions and total maximum daily loads – are a result of wet weather discharges where many of the FIB sources are not from human sources. The Environmental Protection Agency’s (EPA’s) 2012 water quality criteria allows for site-specific criteria when non-human sources predominate, through the use of epidemiology studies (empirical health data) or quantitative microbial risk assessments (QMRA, a risk-based model). Despite the extreme costs of controlling wet weather FIB, no epidemiology studies have been conducted following wet weather to ascertain if there is an increase in risk, and QMRAs have not been conducted synoptically with an epidemiology study for body contact recreation exposures to determine if risk models are adequate predictors of gastrointestinal symptoms.

The goal of this project was to: 1) assess the risk of beachgoers who enter the ocean following wet weather, and 2) compare the empirical epidemiology results to QMRA model output specifically for site-specific objective development. The project was conducted in San Diego, California, where sanitary and storm drain collection systems are separate and 104-105 people enter the ocean following winter storms.

Epidemiology results indicated that there was a risk of entering the ocean following wet weather, averaging 12 excess illnesses per 1,000 exposures. This estimate of risk is lower than the 2012 recreational criteria guidelines from EPA, which stipulates 32 – 36 gastrointestinal illnesses per 1,000 exposures. The QMRA, based on pathogen measurements from the wet weather discharge upstream of the selected beaches, estimated an average 15 gastrointestinal illnesses per 1,000 illnesses, comparable to the empirical epidemiological results.

Kenneth Schiff is SCCWRP’s Deputy Director and is responsible for helping manage day-to-day operations, supervising and mentoring senior level staff, and developing the long-term vision of the research agency. He received his B.S. in biology from San Diego State University in 1984 and his M.S. in biology from California State University, Long Beach in 1988. Schiff joined SCCWRP in August 1995. His research focus cuts across several scientific disciplines and agency departments to assess both environmental and human health risk. The outcome of his research has been widely used in environmental management actions including remediation prioritization and implementation, assessment tool development, testing new technology, and regulatory responses such as NPDES permit conditions, developing TMDLs, and setting water quality standards.

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