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published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution.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.

Discussion The data shown here do not represent assessments of the risks posed to people or ecosystems in any specific location, since they do not incorporate factors such as whether the water tested is actually used as a drinking water source or whether aquatic animals are biologically active at the time of year when the contaminants are found.

The standards and guidelines used in this indicator are useful reference points, but they must be interpreted carefully, since different standards reflect different levels of protection from harm. Furthermore, different standards and guidelines may apply to water, sediments, and fish tissue.

Guidelines for the protection of aquatic life are often numerically lower than standards and guidelines to protect human health. Aquatic animals spend much or all of their life in water, and may be more sensitive to specific contaminants.

People consume drinking water from both streams and groundwater, and they eat fish, so human health standards and guidelines apply to all three. Guidelines to protect aquatic life are not applied to groundwater, and standards and guidelines to protect human health are not applied to either stream or estuary sediments.

Different agencies and programs are responsible for the collection and analysis of data from freshwater systems (streams and groundwater) and estuaries. The objectives of these programs differ, leading to different site selection procedures, suites of contaminants measured, and collection and analysis procedures. Guidelines for freshwater fish are set to protect fish-eating wildlife, and aquatic life guidelines for coastal sediments differ from those for stream sediments. Thus, the results are not directly comparable.

The contaminants that were analyzed in different media (streams, groundwater, etc.) varied, depending on the chemical properties of the contaminants, known environmental occurrence, and potential for adverse effects on people or ecosystems. For example, volatile organic compounds were analyzed in groundwater but not in stream sediments because their chemical properties make it extremely unlikely that they would be found there. Data are not available to compare either fresh or saltwater fish contaminant concentrations with human health/consumption guidelines.

See also the coastal, farmland, and urban contaminants indicators.