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Agency for Toxic Substances and Disease Registry
Polychlorinated Biphenyls (PCB) Toxicity
Who is at Risk
- Recreational and subsistence fishers who eat large amounts of locally caught fish might be at increased risk for exposure to PCBs.
Consumption of contaminated sport fish, particularly bottom-feeding species from waters contaminated with PCBs, increases the level of exposure to PCBs. There is a direct relationship between serum PCB levels and the quantity of contaminated fish consumed. For example, serum PCB levels ranged from 7 parts per billion (ppb) in Michigan residents who ate no fish to a maximum of 366 ppb in persons who ate an average of 40 kg (88 pounds) of fish per year. There is also evidence to suggest that elevations in the serum PCB level are related to historic rather than recent levels of fish consumption (ATSDR 2000a).
- Three other populations are also at risk for increased PCB exposure.
In addition to sport anglers and subsistence fishers (many of whom are American Indians, ethnic minorities, and immigrant populations), three other groups within the general population identified as having either a risk for elevated exposure or increased physiologic sensitivity to PCBs (ATSDR 2000a).
- The offspring of low income subsistence fishers mothers who ate large amounts of contaminated fish or wild game while pregnant.
Fetuses and neonates are potentially more sensitive to PCBs than are adults because the hepatic microsomal enzyme systems that facilitate the metabolism and excretion of PCBs are not fully functional. In addition, infants and young children consume a greater amount of food per kilogram of body weight and therefore have a proportionately greater exposure to PCBs than do adults eating food with the same level of contamination (ATSDR 2000a). PCBs are lipophillic and there is placental transfer increasing the body burden.
- Farmers and their families who consume PCB-contaminated food via their own farm-raised beef and dairy cattle.
During the 1940s and 1950s, the inside of concrete silos on many farms in the Midwest were coated with sealants containing PCBs. Over time, these sealants peeled off and became mixed with silage used to feed beef and dairy cattle. Farmers and their families who lived on these farms and who regularly ate farm-raised beef and dairy products were exposed to PCBs. Although most of these silos have been dismantled and removed, the remaining silos represent a potential source of exposure to PCBs (ATSDR 2000a).
- People living near incinerators, other PCB-disposal facilities, or NPL hazardous waste sites where PCBs have been detected.
Persons living near incinerators, other PCB-disposal facilities, or any of the 432 current or former hazardous waste sites on the EPA NPL at which PCBs have been found are also at increased risk for exposure to PCBs (ATSDR 2000a).
- Persons with compromised hepatic function might metabolize PCBs less efficiently than healthy persons.
Because PCBs are metabolized mainly in the liver, persons with impaired hepatic function might be at increased risk because of their diminished ability to detoxify and excrete these compounds. Persons with incompletely developed glucuronide conjugation mechanisms (such as those with Gilbert syndrome or Crigler-Najjar syndrome) fall into this category, as do those with chronic liver diseases such as cirrhosis or hepatitis B. Because they temporarily decrease glucuronide synthesis, hepatic infections can increase a persons sensitivity to PCBs, as can the use of medications that are potentially toxic to the liver (ATSDR 2000a). Similarly, because hepatic function normally declines with age, elderly persons are also more susceptible to the effects of PCB exposure.
- Although PCBs are no longer manufactured in the United States, some workers can be exposed during repair of older equipment and accidents or spills.
Although PCBs are no longer manufactured in the United States, a potential for workplace exposure exists. Workers can inhale or have dermal contact with PCBs during the repair or routine maintenance of older equipment or electrical transformers and during accidents or spills involving PCBs. Exposure can also occur during the disposal of PCB-containing materials at hazardous waste sites. Occupations with risk for PCB exposure include, but are not limited to
- electric cable repair,
- electroplating,
- emergency response,
- firefighting,
- hazardous waste hauling/site operation,
- heat exchange equipment repair,
- maintenance cleaning,
- medical laboratory technician/technologist,
- metal finishing,
- noncellulose fiber industry,
- paving and roofing,
- pipefitting/plumbing,
- semiconductor and related industries,
- timber products manufacturing,
- transformer/capacitor repair, and
- waste oil processing.
| 2. |
Are other sources of PCB exposure likely for the patient described in the case study? |
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