A wall of coal fly ash contaminated with<unk> s, resulting from the release of 5.4 million cubic yards of coal fly ash slurry into the Emory River, Tennessee, and nearby land and water features, in December 2008. Testing showed significantly elevated levels of arsenic, copper, barium, cadmium, chromium, lead, mercury, nickel, and thallium in samples of slurry and river water. Cleanup costs may exceed $1.2 billion. A<unk>  is any relatively dense<unk>  or<unk> loid that is noted for its potential toxicity, especially in environmental contexts. The term has particular application to cadmium, mercury and lead, all of which appear in the World Health Organization's list of 10 chemicals of major public concern. Other examples include manganese, chromium, cobalt, nickel, copper, zinc, silver, antimony and thallium.<unk><unk> s are found naturally in the earth. They become concentrated as a result of human caused activities and can enter plant and animal (including human) tissues via inhalation, diet, and manual handling. Then, they can bind to and interfere with the functioning of vital cellular components. The toxic effects of arsenic, mercury, and lead were known to the ancients, but methodical studies of the toxicity of some<unk><unk> s appear to date from only 1868. In humans,<unk><unk>  poisoning is generally treated by the administration of chelating agents. Some elements otherwise regarded as<unk> s are essential, in small quantities, for human health.
Toxic heavy metal
Hazardous drugs
Toxicant
Chronic toxicity
Persistent organic pollutant
Toxic alcohol
Acute toxicity
Drug 