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Development and validation of same-day monitoring methods for recreational water

Every year, thousands of Americans take trips to recreational beaches to splash or swim in the water. When water is polluted, swimmers can become ill from exposure to waterborne pathogens. Culture-based laboratory methods to monitor microbial water quality require overnight incubation to determine whether water is safe for swimming. To reduce the number of swimming-related illnesses, beach managers need quicker ways to determine when beaches are unsafe for swimming and should be closed.

In response, EPA scientists have developed new rapid quantitative molecular-based methods for Enterococcus, which is a type of fecal indicator bacteria. EPA Method 1611 and updated Method 1609.1 use quantitative polymerase chain reaction (qPCR) technology to extract and quantify DNA from Enterococcus in water samples. These new methods produce results in less than four hours rather than the 24 hours required by culture-based methods, which gives beach managers the ability to alert beach-goers to unsafe levels of microbial contamination on the same day that the sample is taken.

The qPCR method has been tested in numerous EPA epidemiological studies at freshwater and marine beaches to determine whether a consistent relationship exists between rates of swimming-related illness and the water quality data produced. These studies, along with performance research, have found that the qPCR method is a reliable means for detecting fecal indicator bacteria in recreational waters.

As a result of these studies, EPA's 2012 Recreational Water Quality Criteria includes information for states that want to adopt water quality standards based on the Enterococcus spp. qPCR methods and provided Beach Action Values (BAVs) for this method for use in beach notification programs. Use of these new EPA methods will result in earlier public notification of health hazards at beaches and a potential reduction in the number of swimming-related illnesses due to exposure to waterborne pathogens.