Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

The Indicator

The most commonly used indicators of fecal contamination are total coliform bacteria, fecal coliform bacteria, Escherichia coli, and Enterococcus (the latter two are bacteria as well). Although indicator bacteria do not necessarily cause illness, they are abundant in human waste where pathogenic organisms, such as viruses and parasites, are also likely to exist. Bacterial indicators are currently measured instead of pathogenic organisms because the indicators occur in much larger numbers and can be measured with faster, less expensive methods than the pathogens of concern. However, with advances in biotechnology, it may soon be feasible to monitor pathogens using genetic tests.

This indicator focuses on Enterococcus, which was selected over other measures of bacteria because it has been shown to be the most closely correlated with human health effects. The U.S. Environmental Protection Agency (EPA) recommended the use of Enterococcus as the fecal-indicator bacteria for recreational water quality standards in 1986, but it is still not as widely used as the coliform measures. The reporting categories for this indicator correspond to the daily (104 cells per milliliter of water) and monthly (35 cells per milliliter) geometric mean thresholds suggested by EPA as national beach water quality standards. It should be noted that the selection of Enterococcus is logical today based on EPA guidelines; however, it is possible that new recommendations from EPA and other sources may alter the organism(s) reported in this indicator (for a discussion of a multi-organism indicator, see http://www.healthebay.org/beachreportmethod.asp).

Because some events are short-term but extend over large areas and others are chronic closures in small areas (near a small local source, for example), the indicator is based on the number of beach-mile-days exceeding thresholds of concern, rather than on the number of exceedances or closures. These different scenarios would be weighted inappropriately if the measure were limited to the number of events or to the mileage of beaches that exceeded thresholds at any time during the year.

The indicator is also based on the underlying microbiological data rather than on the number of beach closures or advisories, as is done in EPA’s national report (http://www.epa.gov/OST/beaches/); differences in procedures used by local governments in making closure decisions make such reporting less informative. Moreover, the amount of beach monitoring varies dramatically among states, and an indicator based on the number of closures may focus undue concern on states or beach areas that are the most vigilant.

The Data Gap

In 2000, the U.S. Congress passed the Beaches Environmental Assessment and Coastal Health (BEACH) Act. The Act authorizes EPA to award grants to local entities (states, tribes, and territories) to develop and implement monitoring programs at beaches along the coast, including along the Great Lakes. In response to recent legislation, the state of California is moving toward routine reporting of closures in beach-mile-days. Most other states do not summarize their data in this format.

Only one study has ever estimated the number of beach-mile- days exceeding bacteriological thresholds of concern, and that was a one-time research project (Noble et al. 2000).

There are several challenges to reporting this indicator at a national level. These involve, first, the adoption by states and municipalities of the use of Enterococcus as an indicator bacteria and adoption of the use of beach-mile-days as the unit of reporting. Second, national reporting will require obtaining the microbiological data from the numerous local governments that collect it. The indicator also requires an assessment of the extent of beach monitoring, which will require three additional types of information: an estimate of the number of miles of publicly accessible beach that is available for water-contact recreation, the spatial extent of beach associated with each water quality measurement (e.g., distance to the next measurement location or to the farthest location that would be closed based on results from that sample site), and the time between samples. This can be complex in practice because some programs measure bacteria sporadically based on events such as spills or citizen complaints, and defining how much beach is represented by a sample can be difficult. Most monitoring uses sampling sites a mile or more apart, while closure decisions typically apply to much smaller areas around any given sampling point.

In addition, many of the agencies and organizations that monitor water quality do not store their data electronically, and even those that do so do not use an agreed-upon storage format. There are also considerable differences in the number, frequency, and degree of coverage of sampling among states and even among beaches within individual states. More consistency among sampling efforts across the nation would enhance the value of the measure. EPA is working to solve the data management problem by collaborating with coastal states to produce an annual report on the national extent of beach closures. While this is a start, EPA’s reporting effort focuses only on closures, rather than on the underlying water quality. Since the standards used to determine when a beach is too dirty for swimming vary from place to place, this information cannot provide a consistent picture of water quality nationwide.

References

Noble, R.T., J.H. Dorsey, M. Leecaster, V. Orozco-Borbon, D. Reid, K.C. Schiff, and S.B. Weisberg. 2000. A regional survey of the microbiological water quality along the shoreline of the Southern California Bight. Environmental Monitoring and Assessment 64:435–447.