Glossary

Below are definitions of some of the terms used within this website, as well as information about some of the more common and harmful PBTs. To learn more about many of the PBTs defined below, please visit http://www.atsdr.cdc.gov/ where you will find indepth information.

PBTs: Persistent Bioaccumulative Toxic Substances are highly toxic, long-lasting substances which can build up in the food chain to levels that are harmful to human health and cause environmental harm. These contaminants can be transported long distances and move readily from land to air and water.

Benzo(a)pyrene: (B(a)P) is a member of a class of compounds known as polycyclic aromatic hydrocarbons (PAHs) which generally occur as complex mixtures and not as single compounds. PAHs are primarily by-products of incomplete combustion. These combustion sources are numerous, including natural sources such as wildfires, industrial processes, transportation, energy production and use, food preparation, smoking tobacco, burning wood in fireplaces and woodstoves, and disposal activities such a as open trash burning.

Environmental Protection Agency (EPA): The mission of the U.S. Environmental Protection Agency is to protect human health and to safeguard the natural environment--air, water, and land--upon which life depends.

Mercury: One of the most common and most dangerous PBTs. Mercury is the only metal which is a liquid at room temperature and is quite volatile which means that it evaporates into the air.

Quicksilver: Another name for Mercury, from the fact that it is a bright silver color in its elemental form and is the only metal to remain a liquid at room temperature.

Hexachlorobenzene: Hexachlorobenzene was widely used as a pesticide until 1965 to protect the seeds of onions and sorghum, wheat, and other grains against fungus. It was also used to make fireworks, ammunition, and synthetic rubber. Currently, there are no commercial uses of hexachlorobenzene in the United States.

Toxaphene: Toxaphene is an insecticide made up of hundreds of chlorinated compounds. It is usually found as a solid or gas, and in its original form it is a yellow to amber waxy solid that smells like turpentine. It does not burn and evaporates when in solid form or when mixed with liquids. Toxaphene is also known as camphechlor, chlorocamphene, polychlorocamphene, and chlorinated camphene.

Toxaphene was one of the most heavily used insecticides in the United States until 1982, when it was banned for most uses; all uses were banned in 1990. It was used primarily in the southern United States to control insect pests on cotton and other crops. It was also used to control insect pests on livestock and to kill unwanted fish in lakes.

Mirex: Mirex is an extremely stable and persistent organochlorine insecticide. It has been used primarily to control insect pests. Best known for its use against the fire ant in the Southeastern United States, it has also been used in other countries against termites, ants, and other agricultural pests. Mirex has also been used industrially as a fire retardant.

Octachlorostyrene: A chlorinated PBT that results unintentionally from magnesium production, commercial production of chlorinated solvents, aluminum plasma etching (used in producing microelectronic components), aluminum degassing with hexachloroethane, chlorination of titanium and niobium/tantalum ores, waste incineration, and chlor-alkali production with graphite anodes. It is found in sources concurrently with other toxic chlorinated chemicals, including dioxins and furans.

Aldrin/Dieldrin: Aldrin and dieldrin are insecticides with similar chemical structures. Pure aldrin and dieldrin are white powders with a mild chemical odor. The less pure commercial powders have a tan color. Neither substance occurs naturally in the environment. From the 1950s until 1970, aldrin and dieldrin were widely used pesticides for crops like corn and cotton. Because of concerns about damage to the environment and potentially to human health, EPA banned all uses of aldrin and dieldrin in 1974, except to control termites. In 1987, EPA banned all uses.

Chlordane: Chlordane is a manufactured chemical that was used as a pesticide in the United States from 1948 to 1988. Technical chlordane is not a single chemical, but is actually a mixture of pure chlordane mixed with many related chemicals. It does not occur naturally in the environment. It is a thick liquid whose color ranges from colorless to amber. Chlordane has a mild, irritating smell.

DDT (DDE and DDD): DDT (dichlorodiphenyltrichloroethane) is a pesticide once widely used to control insects in agriculture and insects that carry diseases such as malaria. DDT is a white, crystalline solid with no odor or taste. Its use in the U.S. was banned in 1972 because of damage to wildlife, but is still used in some countries.

DDE (dichlorodiphenyldichloroethylene) and DDD (dichlorodiphenyldichloroethane) are chemicals similar to DDT that contaminate commercial DDT preparations. DDE has no commercial use. DDD was also used to kill pests, but its use has also been banned. One form of DDD has been used medically to treat cancer of the adrenal gland.

Dioxins (and Furans): "Dioxins" refers to a group of chemical compounds that share certain chemical structures and biological characteristics. Several hundred of these compounds exist and are members of three closely related families: the chlorinated dibenzo-p-dioxins (CDDs), chlorinated dibenzofurans (CDFs) and certain polychlorinated biphenyls (PCBs).
Dioxins are formed as a result of combustion processes such as commercial, medical or municipal waste incineration---particularly of certain plastics---and from burning fuels (like wood, coal or oil). Dioxins can also be formed when household trash is burned and as a result of natural processes such as forest fires. Chlorine bleaching of pulp and paper, certain types of chemical manufacturing and processing, and other industrial processes all can create small quantities of dioxins. Cigarette smoke also contains small amounts of dioxins.

Thimerosal: a mercury compound used in solutions as an antiseptic and preservative. Also known as merthiolate or mercurochrome.