Dogs get all the press for being wonderful scent detectors. They can sniff out drugs and bombs, identify cancer and even locate bedbugs.

But who could imagine that the lowly clam would take on a similar role as water based pollution detector?

Really. Clams.

Clams are filter feeders. They draw water into their shells and sieve particles through specialized gills that have evolved to collect food as well as exchange gas.

Over the course of a day, a two inch clam can process up to two gallons of water, collecting food and other materials attached to the food. These other materials, which can include toxins and pollutants, build up in the clam's tissues by a process known as bioaccumulation.

Clams Get Day Jobs

Biologists are putting Asiatic clams to work as tiny pollution detectors in the Anacostia River Estuary east of Washington D.C. to pinpoint where chemicals are getting into the waterway.

Clams are placed in several areas, including locations downstream from industries and farms. After they are given eleven weeks to filter the water, they are taken back to the lab where their tissues can be analyzed for metals, pesticides and other man made industrial pollutants.

Dangerous Pesticides Found

Thanks to the clams, scientists have found chlordane in the water at some locations. This dangerous pesticide used for killing termites was banned twenty years ago, and it's believed that buried supplies may be leaking into the water supply.

Metals, including copper, zinc, iron, chromium, and cadmium have also been detected, as well as man made organic chemicals known to cause cancer such as PCBspolychlorinated biphenylsand PAHspolycyclic aromatic hydrocarbons.

Clams have earned their reputation as pollution detectors, but they'll probably never take over as man's best friend. They might be able to filter, but they just can't fetch.