Phaseout of Toxic Chemicals

In the 21st century, global efforts have emerged toward phasing out the use of toxic and environmentally persistent chemicals. The United Nations has led this effort, focusing on chemicals known to linger in the environment and those that have adverse effects on human and ecosystem health. Most of these chemicals were developed as insecticides but have been found to affect more than their target species.

The largest global action to phase out the use of toxic chemicals is the Stockholm Convention on Persistent Organic Pollutants. This action began in 1995 when the United Nations Environment Programme (UNEP) called for global action to address chemicals that linger in the environment, bioaccumulate, and may adversely affect animals and humans. As a response, a list of 12 chemicals, called the “dirty dozen,” was developed. The original convention was negotiated in 2001 but was not ratified until 2004. There were 151 signatory nations that agreed to the elimination of the following chemicals:

• Aldrin: An organochloride insecticide used to treat seed and soil, aldrin has a similar structure to dieldrin. Aldrin quickly breaks down to Dieldrin in the environment and in bodies. It has been banned from use in the United States since 1978.
• Chlordane: An organochloride pesticide used on lawns, gardens, and for crops that was limited to termite control within the United States by the Environmental Protection Agency in 1983. It has been associated with breast, prostate, brain, and blood cell cancers. It is suspected that more people may suffer the noncancerous health effects of chlordane, which include migraines, respiratory infections, diabetes, anxiety, depression, and activated immune system.
• Dieldrin: A chlorinated hydrocarbon developed as a pesticide alternative to DDT, dieldrin has been associated with Parkinson's, breast cancer, and damage to the immune, reproductive, and nervous systems. It has been banned from use in the United States since 1978.
• Endrin: An organochlroide used to control insects and rodents, endrin has been associated with respiratory disease. Acute poisoning affects the human nervous system, and it has caused mass poisonings worldwide, with children especially susceptible. Endrin has not been produced in the United States since 1986.
• Heptachlor: Heptachlor is an organochloride insecticide used in homes, buildings, and crops. Since 1988, its use has been limited in the United States to the control of fire ants in [Page 378]underground transformers. It is a possible human carcinogen and has been associated with liver tumors. When exposed in vitro or early infancy, heptachlor may affect the immune and nervous systems, result in lower weight, or even death.
• Hexachlorobenzene: A cholorocarbon fungicide used until 1965 to protect seeds or control wheat bunt (a fungal infection), hexachlorobenzene has other uses, including the manufacture of ammunition, synthetic rubber, and fireworks. In Turkey, in the 1950s, high death rates occurred among young children and nursing infants of mothers who ate grain exposed to hexacholorbenzene. It has been associated with damage to the liver, bones, kidneys, blood, and the immune, endocrine, and nervous systems when ingested over time.
• Mirex: Mirex is a chlorinated hydrocarbon used in the past to control fire ants and also as flame retardant (under the name Dechlorane) for electrical goods, paint, paper, rubber, and plastic. In 1978, the use and production of mirex was banned in the United States. Mirex has been associated with harmful effects to the liver, kidneys, stomach, intestines, eyes, miscarriage, and thyroid, nervous, and reproductive systems. Acute exposure may cause irritability, trembling, blurry vision, and headaches.
• Toxaphene: All uses of Toxaphene, an insecticide that contains more than 670 chemicals, formerly used to control insects on cotton, livestock pests, and undesired lake fish, were banned in the United States in 1990. It can damage the lungs, nervous system, adrenal glands, immune system, liver, and kidneys and can cause death. It is a probable human carcinogen and may affect fetal development.
• PCBs (polychlorinated biphenyls): PCBs are a class of organic compounds including up to 209 possible congeners. PCBs were widely used as dielectric fluids in transformers, capacitors, and coolants. Their manufacture has been banned in the United States since 1977. PCBs are probably carcinogenic to humans and can cause cancer in animals. They have also been associated with adverse developmental, reproductive, dermatologic, hepatic, immunologic, and endocrine effects.

The nations also agreed to only utilize DDT (dichlorodiphenyltrichloroethane) for malaria control, and eliminate its use as a pesticide. DDT was used to control malaria and typhus during World War II. After the war, it was used widely as a pesticide. Rachel Carson's 1962 book Silent Spring proposed that DDT not only killed pests but also killed beneficial insects and birds and could cause cancer in humans. The resultant public outcry led to a 1972 ban of DDT for use in the United States. Due to its effectiveness at controlling mosquitoes, the Stockholm Convention agreed to limit its use to malaria control. Several developing countries had almost eliminated malaria in the 1960s through the use of DDT, but when use of DDT ceased, the disease returned. In 2006, the World Health Organization endorsed the use of DDT to control malaria. Limited application of DDT for malaria reduces environmental exposure and includes only spraying the inside walls of houses, and is supported by several environmental groups, such as the Sierra Club. Since 2006, the use of DDT in Africa is thought to be on the rise, and some scientists have expressed concerns of the possible health effects to humans exposed to DDT in their homes.

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