9.1 Effects
Most of the data on livestock were on the effects of PCBs in their feed. Hansen et al. (1975) found adverse effects in third-litter sows which were fed 20 µg Aroclor 1254/g of feed (wet weight) throughout the gestation and nursing periods. Treated sows also had more mummified foetuses. These investigators found that the total PCB levels in blood, brain, kidney, and ovarian tissues were less than 0.5 mg/kg (wet weight), but ranged from 4 to 20 mg/kg (wet weight) in the fat tissue.
Chickens exposed to 2 µg Aroclor 1254/g in their diet for 14 weeks showed a reduction in number of eggs laid (Platonow and Reinhart, 1973). PCBs (e.g., Aroclor 1254) at a concentration as low as 0.1 µg/g in the feed have also been shown to alter enzyme levels in the liver of chicken and quail (Srebocan et al., 1977). Strachan (1988) suggests that these effects are probably reversible and are not necessarily adverse in themselves to the well-being of the individual birds. They are, however, symptomatic of birds under stress and consequently, PCB dosages causing stress should be considered adverse.
No data were found in the literature regarding toxicity of PCBs to livestock from drinking water. The concentration of PCBs in ambient waters generally ranges from low to undetectable (section 4.1.1).
9.2 Criteria from the Literature
No criterion for livestock watering was recommended in the literature.
9.3 Recommended Criteria
Criteria for PCBs in waters consumed by livestock are not recommended at this time.
9.4 Rationale
Criteria for PCBs in waters consumed by the livestock are not recommended at this time for two reasons: (i) the lack of pertinent information (e.g., the toxicity of PCBs in water to livestock), (ii) the concentration of PCBs in ambient waters generally ranges from low to undetectable (section 4.1.1). As a result, it is believed that an exposure to the ambient waters (with PCB concentrations similar to those recommended for the protection of aquatic life) will not contribute significantly to PCB residues in livestock. This argument is further supported by a worst-case scenario presented in Table 20, which suggests that a fairly long-term exposure to contaminated waters is necessary to accumulate PCBs in livestock tissue to the level recommended by Health and Welfare Canada.
TABLE 20
Accumulation of PCBs in livestock tissue from drinking water.
__________________________________________________________________
Assumptions:
Daily accumulation of PCBs in the fat tissue = (10 ng/L) x (60 L/d) / (450 kg live weight x 0.10 fat/live weight x 1000 g/kg) = 0.0133 ng PCBs/g/d
Time required to accumulate levels equal to the guideline of 0.2 µg PCBs/g-fat = (0.2 µg/g) x (1000 ng/µg) / (0.0133 ng/g/d) x (365 d/a) = 41 years
__________________________________________________________________