Reported January 2009

BIOACCUMULATION AND CLAMS: Clams are filter-feeders, meaning they draw water into their shells, remove the food they find, and then draw in more food-rich water to continue feeding. This means lots of water works its way through their shells. The muscle of the clam gathers not only food, but other material suspended in water during this process, which can lead to the accumulation of toxins and pollutants. Bioaccumulation is the term for toxins and pollutants that collect in the tissue of an organism. Biomagnification is a related term, referring to the transfer of such substances from prey to predator. If a prey animal bioaccumulates toxins in its body, then its predator, after consuming many of the smaller animals, will accumulate many, many times the amount of the toxin in any one of their prey.

SECONDARY STANDARDS: Even if your tap water meets the EPA's basic requirement for safe drinking water, some people still object to the taste, smell or appearance of their water. These are aesthetic concerns, however, and therefore fall under the EPA's voluntary secondary standards. Some tap water is drinkable but may be temporarily clouded because of air bubbles, or have a chlorine taste. A bleach-like taste can be improved by letting the water stand exposed to the air for a while.

The American Geophysical Union contributed to the information contained in the TV portion of this report.

If you would like more information, please contact:

Harriette L. Phelps
Biology Professor Emeritus
Greenbelt, MD 20770
University of the District of ColumbiaT
(301) 441-2207
hphelps@hers.com

Peter Weiss
American Geophysical Union
Washington, DC 20009-1277
1-800-966-2481
http://www.agu.org
pweiss@agu.org

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