Glossary

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Industrial Chemicals

Industrial Chemicals Organic solvents, industrial chemicals, and byproducts of industrial processes have been shown to cause loads of health problems. Exposure to some of these chemicals has also been associated with increased breast cancer risk. Like so many other environmental chemicals, these substances probably exert some of their carcinogenic effects by interfering with cellular processes in breast tissue that are normally regulated by the hormone estradiol.

What are the chemicals that are causing concern and where are they found?

Organochlorines are chemicals produced for various consumer purposes. Both organochlorine pesticides and polychlorinated biphenyls (PCBs) are examples of these chemicals. PCBs are good insulating material and have been widely used as coolants and lubricants in transformers, capacitors, and other electrical equipment. Because of previous widespread use, PCBs are also found in food, surface soils, drinking and groundwater, indoor air and in some industrial settings.

Industrial byproducts are chemicals produced unintentionally through industrial processes. Dioxins, a group of hundreds of chemicals, are the unintentional byproduct of burning coal and oil and are also formed when chlorine-containing chemicals, like plastic or industrial waste, are burned. Dioxin is also formed during chemical and pesticide manufacturing and pulp and paper bleaching. These chemicals are now found everywhere in the world in water, air, soil, and sediment. They are also a contaminant in food.

Organic solvents such as benzene, toluene, trichloroethylene, and tetrachloroethylene are used in a variety of industrial processes. Solvents are used in the manufacturing of computer components, cosmetics manufacturing, the semiconductor industry, the fabrication of metal, and in the lumber, furniture, printing, chemical, textile, and clothing industries. Tetrachloroethylene, also known as perchloroethylene (PCE or PERC), is an organic solvent used in the dry cleaning process. It is a contaminant of both air and water and is also present on recently dry-cleaned clothes.

How do these chemicals enter the body?

In general, industrial chemicals, byproducts, and solvents enter the environment when they are produced and disposed of during industrial processes. These chemicals are present in the air, water, soil, in products found and used in the home, and in the food supply. Exposure occurs when contaminated air is inhaled, when water is used for drinking, cooking, or bathing, and when contaminated food is ingested. People who work in industries where these chemicals are used may also be exposed on the job.

The single most significant source of exposure to PCBs for people is their food. Some exposures also occur through the ingestion of contaminated surface soils, drinking and groundwater. Inhaling indoor air may also result in exposure to PCBs if older fluorescent lights are used.

The major source of exposure to dioxins is through the food supply [Charnley & Doull, 2005]. Like many environmental chemicals, dioxins are fat-soluble and are present in the fat of animals. When we eat meat and dairy products, especially from animals that have eaten contaminated meat or plants themselves, then we are more likely to ingest higher amounts of these chemicals.

Organic solvents can enter the human body by ingestion, inhalation, and absorption through the skin, with inhalation being the primary route of exposure. Absorption through the skin can also be a significant route of exposure when the skin is immersed in solvents, possibly resulting from occupational exposures [Labreche & Goldberg, 1997].

What are the mechanisms by which these substances might increase the risk for breast cancer?

PCBs are a diverse class of compounds and can have multiple effects on cells. One class of PCBs acts like an estrogen. A second class acts like an anti-estrogen and a third type appears not to be hormonally active, but can stimulate enzyme systems of animals and humans. As a result, PCBs as a whole have the ability to alter normal metabolism, either by hormonal disruption or enzyme changes [Spink et al., 2002]. In some cases, PCBs may bind to the estrogen receptor and activate DNA binding and alter gene expression [Brouwer et al., 1999]. Some PCBs also have the ability to induce DNA damage that can be detected in the cells of human breast cancer tissue [Oakley et al., 1996].

Dioxin has been shown to disrupt multiple chemical pathways in the regulation of DNA transcription. In this sense, dioxin appears to function as do many hormones, initiating a cascade of events that is dependent upon the environment of each cell and tissue [Birnbaum, 1994]. Dioxin may also enhance the production of hormonal metabolites that may subsequently cause DNA damage [Lucier et al., 1993].

Organic solvents are readily absorbed and distributed through the body via the bloodstream. These chemicals can then accumulate in the breast due to the high proportion of fat tissue present there. Once in the breast, organic solvents can damage DNA directly or indirectly through their metabolites. Highly reactive metabolites of these chemicals may persist long enough to exert detrimental effects on the DNA [Labreche & Goldberg, 1997].

There are indications that this DNA damage may occur in the milk-producing glands that constitute the lobules and are connected to the duct system, the areas of the breast where cancer usually begins.