EPA publishes criteria for reduction of eutrophication

The US Environmental Protection Agency is taking a major step to protect waters from excessive nutrients by introducing water quality criteria for nutrients, including nitrogen and phosphorus.

The criteria will serve as recommendations to states and tribes for water-based nutrient standards. States are expected to adopt or revise nutrient standards by 2004, based on the new criteria.

The EPA expects the new standards will significantly reduce nutrients in US waterways. Nutrients were recognised as a leading cause of water pollution in a l998 water quality report to Congress, which showed that 40% of US rivers – some 84,000 miles – were suffering because of nutrient enrichment. Fifty-one percent of the lakes and reservoirs – covering 3.5 million acres – and 57% of the estuaries in the survey were similarly adversely affected. Nutrients were also implicated in the development of two large hypoxic zones in the Gulf of Mexico, as well as in several East Coast state waters. Nutrients were also linked to Pfiesteria-induced fish kills and human health problems associated with the coastal waters of several East coast and Gulf states.

A national strategy was developed as part of a federal initiative in 1997, when vice president Al Gore requested that the EPA develop a comprehensive action plan to build on the administration’s clean water successes. The plan was to address three major goals: enhanced protection for public health from water pollution; better control of polluted runoff; and promotion of water quality protection on a watershed basis.

The new standards were developed as a result of the national strategy, which developed nutrient information and worked with states and tribes to adopt the criteria as part of state water quality standards. The strategy provided eutrophication assessment tools and took into account the ability of the various organisations involved to conduct assessments at the level of regional watersheds and water bodies.

The strategy’s approach was to use a regional and water body-type approach to develop the nutrient criteria. Technical guidance documents for streams and rivers, lakes and reservoirs, estuaries and coastal waters and finally, for wetlands, were developed as ‘user manuals’ to help states and tribes assess levels of enrichment.

An EPA National Nutrient Team, with regional nutrient co-ordinators, was also established to develop the regional databases and promote state and tribal involvement. The criteria were developed in the form of numerical regional target ranges which will be used in the development of water quality criteria, standards, permitted discharge limits and total maximum daily loads. The nutrient management programs will be monitored and evaluated for effectiveness as they are implemented.

EPA has also issued an updated water quality criterion for methylmercury, the form of mercury found in contaminated fish, which is toxic to the nervous system. Methylmercury is absorbed by plant and aquatic life and accumulates in fish, which can then enter the food chain.

EPA is issuing the criterion, which has not been updated since 1980, under the Clean Water Act. It will be used by states in determining methylmercury levels in fish tissue. The new methylmercury criteria are based on risk assessment via a reference dose developed by the EPA in response to a recommendation last summer by the National Academy of Sciences. Both the new criteria and the new reference dose are based on updated scientific data on the environmental fate and human health effects of methylmercury.

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