Organochlorines (OCs)
Organochlorines (OCs) are a group of chemical compounds formed through the chlorination of hydrocarbons, characterized by their stability, toxicity, and tendency to accumulate in fatty tissues. These substances are prevalent environmental contaminants found in food, air, water, soil, and even breast milk, and they pose significant health risks, particularly to vulnerable populations such as embryos and nursing infants. OCs have been associated with a range of adverse health effects, including various cancers, reproductive and developmental issues, and neurotoxicity. Historically, OCs were widely used in insecticides, herbicides, and various consumer products, but their use has decreased since the mid-20th century due to growing awareness of their dangers, particularly following the publication of Rachel Carson's "Silent Spring." Despite bans on many OCs in developed countries, residues remain in the environment and continue to expose humans and wildlife. Current research suggests a persistent link between OCs and several types of cancer, highlighting the need for ongoing study into their long-term effects on health and ecosystems. Understanding the legacy and ongoing presence of OCs is crucial for public health and environmental safety.
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Organochlorines (OCs)
ALSO KNOWN AS: Environmental, occupational, developmental, neuro-, and reproductive toxicants
DEFINITION: The chlorination of hydrocarbons produces organochlorines (OCs), which are chemically stable, fatty, and toxic. OCs accumulate in fat and thus are transported via the food chain to top carnivores, including fish, birds, predaceous mammals, and omnivores such as humans. OCs are common contaminants in food, air, water, soil, and breast milk. They comprise diverse subgroups, members of which cause various types of health effects ranging from acutely fatal to chronically toxic over generations. Many OCs cause liver hypertrophy and cancer; neurotoxic, embryotoxic, reproductive, developmental, and immunotoxic effects; and various types of cancers in the pubescent children of exposed mothers.
OCs are produced by the chlorination of some of the petroleum hydrocarbons and can remain in the environment for decades after being introduced. Although they are used less in the twenty-first century, they were once common in insecticides, fungicides, herbicides, miticides, polychlorinated biphenyls (PCBs), flame retardants, metal cleaners, dry-cleaning solvents, polyvinyl chloride (PVC) and other plastics, paints, dyes, synthetic intermediates, refrigerants, rayon and cellulose manufacturing, detergents, degreasers, disinfectants, halothanes, soft PVC surgical equipment, medicines—at one time thousands of everyday products contained them or used them in the manufacturing process.
The manufacture, use, and disposal of OCs create environmental and health problems. For example, for only one polymer, PVC, the downstream export of products from its synthesis in 2009 amounted to about 12.1 billion pounds. In another example, at one time, the pulp and paper industries in North America produced more than 100 million tons of OCs. The waste by-products that pose the most serious health and ecosystem risks of the manufacturing process include PCBs, polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated diphenyl ethers (PCDEs). Other notorious OCs include the pesticides dichlorodiphenyltrichloroethane (DDT) and dichlorodiphenyldichloroethylene (DDE), cyclodiene insecticides, Mirex, hexachlorobenzene, hexachlorocyclohexanes, and various solvents.
PCBs are mixtures of various congeners and isomers, which are chemically stable, viscous, and low-volatile. They have caused widespread contamination in everything from agriculture to office buildings, automobiles, and homes. Major environmental sources of PCBs include manufacturing wastes, careless waste disposal, and dumping.
Related cancers:Liver cancer, testicular cancer, breast cancer, soft-tissue sarcoma, non-Hodgkin lymphoma, leukemia, and pancreatic cancer
Exposure routes: Food, air, water, mother’s milk
Where found: Air, water, food, breast milk
At risk: Those at highest risk for cancers associated with organochlorines (OCs) include embryos, fetuses, suckling newborns, and adults who are occupationally exposed to or living in the vicinity of the sources of release.
Etiology and symptoms of associated cancers: Organochlorines constitute one of the most diverse groups of cancer-causing chemicals, considering their volume, categories of use, and persistence. OCs exert both specific and broad-spectrum effects. Out of all known effects, dioxin-like effects are the most serious cause of public concern: estrogenic effect leading to breast cancer; testosterone degradation leading to male infertility; nervous system damage leading to neurobehavioral deficits in offspring of mothers exposed to OCs; immunosuppression issues; development problems (lower birth weights, shorter gestation, congenital disabilities); and occurrence of other types of cancers.
Both US and European farmworkers exposed to OC pesticides have a six times higher risk of getting testicular cancer. Many workers involved in the manufacture of 2,6-di-tert-butyl-p-cresol (DBPC; commonly used as a food preservative) have high OC concentrations in their bodies, low sperm count, and no children. Similarly, in a 2011 literature review, W. Mnif et al. noted that several studies had found that men who are occupationally exposed to OC pesticides have up to a 40 percent higher risk of developing prostate cancer than the general population. Twenty-two OCs are disruptors, mimic estrogens (xenoestrogens), and induce an enzyme that degrades testosterone. The US Environmental Protection Agency reports that an estimated one billion pounds of farm pesticides are applied in the United States annually. Such chemicals may act as xenoestrogens, which can also lead to breast cancer and other hormonal effects.
In the United States, DDE residues in women’s fat can be transferred to the fetus or a baby through breast milk and cause testicular cancer in their sons. OC effects are elevated in the womb and just after birth due to fat mobilization. Nursing infants get as much as 10 percent of their lifetime’s dioxin exposure via the intake of breast milk; however, the half-life appears to be shorter in infants and young children than in adults.
The stunning rise in breast cancer since the 1950s has been suspected to be related to only a few OCs. DDE, PCBs, and DDT are suspected of being involved in human breast cancer and have been found in the fat and serum of women with breast cancer. Although some studies dispute the carcinogenicity of PCBs and claim PCB exposure is not associated with breast cancer, In the Report on Carcinogens, Fifteenth Edition (2021), DDT and PCBs are labeled as reasonably anticipated human carcinogens. PCBs and DDE also appear to be linked to non-Hodgkin lymphoma.
History: Organochlorines do occur, although very rarely, in nature and are usually associated with high-temperature events such as forest fires and volcanoes. People started using and manufacturing OCs in the late 1800s. They were heavily introduced into the environment with the beginning of widespread use of pesticides, particularly DDT, in 1939.
Several billion tons of OCs have been used since World War II, and their residues are present in humans and the environment. Rachel Carson’s 1962 bestseller, Silent Spring, sounded the alarm for the public about the dangers of pesticides in the environment. Production and usage of OC pesticides started declining in the 1970s and 1980s, and many suspected carcinogens were banned in the United States and later throughout much of the world. However, some developing countries continue to use them. Millions of tons of OCs per year were still being produced in the twenty-first century.
Organochlorine residues remain in the environment (air, water, land) and thus in human food and breast milk for decades. Residues of pesticides banned in the 1970s were still present in the food supply in the early twenty-first century. Although many OCs have been banned, others are still registered for use. Increased study of the relationship between OCs and cancer is necessary.
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