Introduction

Although PCBs are no longer manufactured in the United States, people can still be exposed to them. The two main sources of exposure to PCBs are the environment and the workplace.

Because they are resistant to degradation, highly chlorinated PCB compounds can persist in the environment for decades. However, over the past two decades, concentrations of PCBs in most environmental media generally have decreased.

Non-Occupational Exposure: General Population

Food is the main source of exposure to PCBs for the general population (CDC 2009b). Exposure occurs primarily by ingesting high-fat foods—such as dairy products, eggs, and animal fats—and some fish and wildlife [ATSDR 2000; CDC 2009b; Fisher 1999; Gunderson and Gunderson 1988; Hopf et al. 2009; Patterson et al. 2008].

CDC publishes the National Report on Human Exposure to Environmental Chemicals. This report is an ongoing assessment of the exposure to environmental chemicals in the general U.S. population. The Fourth Report (CDC 2009b) contains data for years 1999-2000, 2001-2002, and 2003-2004 from participants in National Health and Nutrition Examination Survey (NHANES). Detailed information on NHANES is available at http://www.cdc.gov/nchs/nhanes/about_nhanes.htm.

Serum concentrations of PCBs were found to reflect cumulative past exposure in the general U.S. population [ATSDR 2011].

Non-Occupational Exposure: Bioaccumulation and Dietary Exposure

In aquatic environments, the high lipophilicity of PCBs causes these compounds to partition out of the water and become adsorbed preferentially to sediments. Although sediment adsorption helps prevent the contamination of drinking-water supplies, the partitioning of PCBs to sediments plays a role in the tendency of these compounds to become concentrated in aquatic organisms. Bottom-feeding fish ingest and accumulate PCBs from sediment. The resistance of these compounds to biodegradation causes PCBs to become more concentrated as they move upward through the food chain from the bottom-feeding organisms. As a result of this bioconcentration and biomagnification, PCB levels in aquatic organisms can be as much as one million times higher than the levels in the aquatic environment [ATSDR 2000].

In the National Study of Chemical Residues in Fish conducted between 1986 and 1989 [EPA 1992a, 1992b], the mean concentration of PCBs in bottom-feeding and game fish was 1.9 parts per million (ppm). However, PCB levels as high as 20 ppm have been detected in game fish taken from waters near hazardous waste sites [ATSDR 2000].

Non-Occupational Exposure: FDA Studies

The U.S. Food and Drug Administration (FDA)'s Total Diet Studies have revealed that total PCB levels have shown a downward trend in concentration from the middle 1970s to the middle 1980s and a relatively steady intake from 1982 to 1997. For example, total diet studies conducted from 1982 to 1984 for adults between the ages of 25 and 30 indicated that the mean daily intake of PCBs was <0.001 micrograms/kilograms (μg/kg) body weight/day while in the 1997 study, the mean was 0.002 μg/kg body weight/day [ATSDR 2000].

Non-Occupational Exposure: Special populations

People living near incinerators, other PCB-disposal facilities, or NPL hazardous waste sites where PCBs have been detected may receive higher PCB exposures than the general population. These exposures may be through ingestion, inhalation, or skin contact [ATSDR 2000].

Do-it-yourselfers repairing or removing older construction materials, including plaster, paint, and caulk, that contain PCBs.

Occupational Exposures: Inhalation and Dermal

Occupational exposure to PCBs occurs mainly via the inhalation and dermal routes.

Commercial PCB mixtures vary from colorless to dark brown oils, and from viscous liquids to sticky resinous semisolids. Although PCBs evaporate slowly at room temperature, the volatility of PCBs increases dramatically with even a small rise in temperature. Equipment that contains PCBs can overheat and vaporize significant quantities of these compounds, creating an inhalation hazard that can be magnified by poor ventilation.

Because of their highly lipophilic nature, PCBs also can be absorbed through the skin following contact with contaminated equipment, water, or soil.

Products that contain PCBs are no longer manufactured, thus occupational exposure no longer occurs in those settings. However, it might occur

• During the maintenance or repair of old equipment that contains PCBs,
• As a result of accidents involving such equipment [Schecter AJ and Charles 1991; Wolff 1985], or
• During waste-site cleanup or disposal activities [ATSDR 2000; Luotamo et al. 1993; Schecter A et al. 1994].
• During repair or removal of older construction materials, including plaster, paint, and caulk that contain PCBs.

Today, PCBs are found mainly in transformers and capacitors manufactured before 1977. Such transformers and capacitors might be found in

• Old industrial equipment (e.g., welding equipment),
• Medical equipment (e.g., x-ray machines), and
• Household appliances (e.g., refrigerators, microwaves and televisions).

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