<unk>  warning label on a power transformer known to contain<unk> s<unk> s <unk> s) are a highly toxic product whose production was banned by United States federal law in 1978, and by the Stockholm Convention on Persistent Organic Pollutants in 2001. It is an organic chlorine compound with the formula C12H10−xClx.<unk> s were once widely deployed as dielectric and coolant fluids in electrical apparatus, carbonless copy paper and in heat transfer fluids. Because of their longevity,<unk> s are still widely in use, even though their manufacture has declined drastically since the 1960s, when a host of problems were identified. With the discovery of<unk> s' environmental toxicity, and classification as persistent organic pollutants, their production was banned by United States federal law in 1978, and by the Stockholm Convention on Persistent Organic Pollutants in 2001. The International Agency for Research on Cancer (IARC), rendered<unk> s as definite carcinogens in humans. According to the U.S. Environmental Protection Agency (EPA),<unk> s cause cancer in animals and are probable human carcinogens. Many rivers and buildings, including schools, parks, and other sites, are contaminated with<unk> s and there has been contamination of food supplies with the substances. Moreover, because of their use as a coolant in electric transformers,<unk> S still persist in built environments. Some<unk> s share a structural similarity and toxic mode of action with dioxins. Other toxic effects such as endocrine disruption (notably blocking of thyroid system functioning) and neurotoxicity are known. The bromine analogues of<unk> s are polybrominated<unk> s (PBBs), which have analogous applications and environmental concerns. An estimated 1.2 million tons have been produced globally. Though the federal ban was enforced by the EPA as of 1979,<unk> s continued to create health problems in later years through their continued presence in soil and sediment, and from products which were made before 1979. In 1988, Tanabe estimated 370,000 tons were in the environment globally and 780,000 tons were present in products, landfills and dumps or kept in storage.
Polychlorinated biphenyl
Polychlorinated naphthalene
Asbestos
Naphthalene
Nitrobenzene
Vinyl chloride
Polybrominated diphenyl ethers
Alkylphenol