Mercury levels down but still dangerous.

• Position: Contamination

Mercury releases from products in the U.S. have declined dramatically over the last 20 years, but continue to be a significant source of environmental contamination, maintains a study by the Environmental Protection Agency, Washington, D.C. Mercury releases from products contribute nearly one-third of total mercury emissions to the air in the U.S.

These findings offer a new view into the relative magnitudes of the various potential sources of mercury release, which can harm the development of a fetus if the mother is exposed to high levels. Mercury also frequently accumulates in fish populations. A number of highly-used products release mercury throughout their life cycles, often in ways that are difficult to measure directly. Therefore, there are considerable uncertainties about the magnitude of mercury released into the environment that is associated with these goods.

"Mercury-containing products such as thermometers, switches, and dental products release mercury during the product life cycle, including during production, use, and disposal," says environmental scientist Alexis Cain, lead author of the study. "Substance flow analysis can be used to estimate the mercury releases to air, land, and water at different...