HF183 and health risks: Overview of the study design

The SMC launched a four-year study in 2020 to evaluate if and how HF183 can be used to quantify health risks from swimming in contaminated runoff.

Researchers are examining how to reliably and accurately measure human pathogens in runoff, so that illness rates from water contact can be modeled using an approach known as quantitative microbial risk assessment (QMRA).

There are four main tasks that make up the study design:

  • Task 1: Researchers are examining how to refine existing methods for measuring pathogens in stormwater – measurements that are challenging because of stormwater’s complex matrix. This method development work is important not just so that researchers can better quantify pathogen levels in stormwater, but also so that managers can reliably determine when pathogens are not present and thus when stormwater does not pose a health risk.
  • Task 2: Researchers will use the improved data collection methods to measure a suite of viral and bacterial pathogens and indicators at sites across multiple Southern California watersheds. Researchers are targeting up to two dozen sites across five counties over multiple storm events to assess the prevalence of HF183 and pathogens in stormwater.
  • Task 3: Researchers will use a health risk modeling approach known as quantitative microbial risk assessment (QMRA) to model the probability of gastrointestinal illness in swimmers who ingest contaminated water as part of recreational activities in the watersheds. QMRA is approved for such applications by the U.S. Environmental Protection Agency.
  • Task 4: Researchers will use the QMRA modeling work to translate HF183 levels measured in runoff to a degree of human health risk, enabling managers to set HF183 risk benchmarks intended to protect the health of humans who engage in recreational activities in Southern California watersheds. The SMC’s goal in developing the HF183 benchmarks is to produce insights that help managers set priorities for cleanup and remediation activities, not to establish regulatory compliance requirements.