The senators acted shortly after a report was released saying that ozone-destroying chemicals were accumulating faster than expected over North America.

If any step in the synthesis of heme is blocked, an intermediate chemical accumulates in the cell, resulting in oxygen depletion.

Although no longer in use, the chemicals accumulate in the environment and are sometimes found in fish and plants that have been exposed to contaminated water or soil.

When the chemical, glutamate, accumulates in the fluid between brain cells, nerve cells that control motor activity become overexcited and die, the researchers found.

The chemicals, which have similar structures, accumulate in body fat and take decades to break down in the environment.

Pesticides, herbicides and other toxic chemicals accumulated in the environment, including the bodies of humans and other animals.

TWO Federal studies have confirmed fears that many paper mills are discharging dioxin into rivers and that the toxic chemical is accumulating in fish downstream.

These chemicals accumulate and persist in the environment.

The toxic chemicals also accumulated in sediments that settled to the river bottom.

Agency scientists are concerned because the chemical, ammonium perfluorooctanoate, accumulates in human blood and demonstrates toxic properties.