PCBs Polychlorinated biphenyls

3. To what extent are humans exposed to PCBs?

• 3.1 To what extent are humans exposed to PCBs through food?
• 3.2 To what extent are infants exposed to PCBs through breast milk?
• 3.3 To what extent are humans exposed to PCBs through air?
• 3.4 To what extent are humans exposed to PCBs through drinking water?

Humans are mainly exposed to PCBs via food, air and drinking water.

Overview: Levels of human exposure to PCBs and Tolerable Daily Intake (TDI)

3.1 To what extent are humans exposed to PCBs through food?

Consumption of contaminated foods, particularly meat, fish, and poultry, appears to remain the main source of exposure to PCBs although levels in food have decreased since the late 70s.

In the USA, the dietary intake of PCBs by adults continually decreased after the late 70s and reached a low in the late eighties (see table 7). Between 1991 and 1997 a somewhat higher dietary exposure of about 3–5 ng/kg body weight per day for adults and 2–12 ng/kg body weight per day for children was observed. The consumption of PCB-contaminated fish has been shown to increase PCB levels in the body. Levels of PCBs in human blood serum have been linked to the amount of contaminated fish eaten, with average levels in the USA generally between 4000 and 8000 ng/litre of blood serum.

Table 7: Estimated daily dietary intake of PCBs in the USA from 1976 to 1991

In Japan, a study carried out in the late 90s estimated the intake of three dioxin-like (coplanar) PCBs from 120 food items. Highest concentrations were found in fish and shellfish (8.39–25.7 ng/kg wet weight basis). The overall PCB intake from all foods was estimated to be 0.00145 ng/kg body weight per day for an adult weighing 50 kg, which represented a relatively high level of PCB contamination in Japan.

Overview: Levels of human exposure to PCBs and Tolerable Daily Intake (TDI)

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 6.2, Human exposure   and
Section 6.3, Tissue concentrations 

3.2 To what extent are infants exposed to PCBs through breast milk?

The amount of PCBs found in human breast milk has followed a downward trend consistent with the decline in the PCB levels both in the environment and in human tissues. Measurements either consider PCB concentrations in breast milk as a whole or in breast milk fat only. In Canada, the average concentration of PCBs in whole breast milk steadily increased between 1970 and 1982, and then returned to its 1970-value by 1986 (6 000 ng/kg whole breast milk).

In Japan, PCB concentrations found in human milk fat were highest in 1974 and had decreased to about 13% of that level by 1998 (0.2 mg/kg milk fat). Total PCB levels in the breast milk fat of Swedish women also showed a steady decrease (from 0.910 to 0.324 mg/kg milk fat) for the period 1967–1997.

Since the late 80s the average PCB concentrations seen in human milk fat were within a range of 0.2 to 4 mg/kg milk fat.

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 6.2, Human exposure 

3.3 To what extent are humans exposed to PCBs through air?

In cities, the average PCB concentration in outdoor air is typically 5 ng/m³, but concentrations in indoor air tend to be at least 10 times higher. An average adult male would thus take in about 100 ng of PCBs per day if he breathed in urban outdoor air alone and much more if he spent time indoors. Some workers can be exposed to much higher concentrations, for instance in PCB disposal facilities where levels of PCBs in the air can range between 850 and 40 000 ng/m³.

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 6.2, Human exposure 

3.4 To what extent are humans exposed to PCBs through drinking water?

In the USA, PCB levels in drinking water were observed to be lower than 100 ng/litre and sometimes undetectable. The expected exposure of the general US population through drinking water is thus less than 200 ng PCB per day.

In Canada, PCBs have been detected in only 1 out of the 280 municipal drinking-water samples tested, at a concentration of 6 ng/litre (See question 7.3 for effects).

This text is a summary of: IPCS - WHO Polychlorinated biphenyls : Human health aspects. Concise international chemical assessment document 55
Section 6.2, Human exposure