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December 05, 2012
Revised criteria for recreational waters

Under a court order, the EPA has revised its 26-year-old recommendations for recreational water quality criteria (RWQC). The RWQC are developed by the Agency to help states establish water quality standards to protect beachgoers from exposure to water that contains organisms that indicate the presence of fecal contamination.  States are not required to comply with the RWQC.

The EPA says that the illness rates used in the RWQC are derived from the National Epidemiological and Environmental Assessment of Recreational Water (NEEAR) definition of gastrointestinal illness, which is not limited to illnesses that exhibit a fever.

Two indicators

The revised RWQC are based on the use of two bacterial indicators of fecal contamination, E. coli and enterococci.  The magnitudes of the bacterial indicators are described by both a geometric mean (GM) and a statistical threshold value (STV) for the bacteria samples.  The STV approximates the 90th percentile of the water quality distribution and is intended to be a value that should not be exceeded by more than 10 percent of the samples taken.  In addition to magnitude, the guidance indicates that both the GM and STV can be exceeded in terms of duration and frequency. 

The revisions narrow the time period over which the results of monitoring samples may be averaged from 90 days to 30 days.  This produces a more accurate picture of water quality for that time, allowing for speedier public notifications about water quality.  The shortened time period helps account for the effects of polluted runoff caused by heavy rainfall.

Beach-specific criteria

Other elements of the revised RWQC include short-term and long-term measures of bacteria levels to be used together to ensure that water quality is properly evaluated; stronger recommendations for coastal water quality so public health is protected similarly in both coastal and fresh waters; a new rapid testing method that states can use to determine if water quality is safe within hours of water samples being taken; and tools that allow states to predict water quality problems and identify sources of pollution as well as to develop criteria for specific beaches (e.g., epidemiological studies in both marine and fresh waters and quantitative microbial risk assessment). 

Click here for the revised RWQC.

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