EPA believes that better data on sediment quality and direct measurements of chemical concentrations in edible fish tissue are needed. Efforts to gather this information are underway. They are collecting data on the physical and chemical characteristics of sediments, the bioavailability of contaminants, levels of contaminant residues in the tissues of aquatic organisms, and the health of benthic communities. Even if toxic chemicals and metals are present in sediments, they may not be harmful. Bioavailablity is a measure of how likely it is that the contaminants will actually affect living organisms.
Many factors affect the bioavailability of contaminants.
To assess the ecological and human health risks posed by contaminated sediments at a site, it is not enough to measure the types and amounts of pollutants present. Scientists may conduct field surveys to assess the health of benthic communities and the levels of contaminants found in the resident fish species. They may run chemical tests to assess the factors that affect bioavailability, and often times conduct biological tests by actually exposing benthic organisms to the contaminated sediment and observing the results.