Kinetics of polychlorinated biphenyls in Bactrian camels

Abstract

The study aimed to determine the accumulation and depuration of polychlorinated biphenyls (PCBs) in Bactrian camels. Four lactating, two-humped camels (Camelus bactrianus) received 0.8 mg PCBs (1.3 μg/kg body weight) daily for 56 days. Then, the depuration of the animals was monitored for the next 4 months. Milk, blood and hump fat of the camels were sampled every 2 weeks and analyzed. Body weight increased significantly, from approximately 550 to 613 kg, by the end of the study. The fat mass in the humps initially decreased (-2.3 kg, P<0.05) then increased at the end of the depuration period (+2.0 kg, P<0.05). At the end of the exposure period, the concentrations of the indicator PCBs were 1.6 mg/g hump fat, 0.85 mg/g milk fat and 0.56 mg/L blood serum, i.e., ten times over the background level. The concentrations in the hump fat decreased significantly during the depuration period, for congeners 28, 52, 101 and 118, but did not vary appreciably for the heavily chlorinated congeners 138, 153 and 180. The apparently stable concentrations of the heavier congeners may be an artifact of the reduced fat mass in the humps during the first part of the depuration period, combined with fat mobilization, which may mask the reduction of stored PCBs. PCB concentrations in the milk and blood were not significantly reduced during the depuration periods, as they represent the outflow of PCBs from the pool stored in the humps and have a weak affinity for lipophilic compounds, respectively. Therefore, it should be recommended to avoid the consumption of raw fat from camel hump in polluted areas because this organ would easily bioaccumulate organic pollutants during an exposure and store it over an extended period. PCB contaminants in milk would reflect the intensity of the outflow from the stored pool, and it would take a longer time in camels than in other ruminants to obtain safe food after the exposure of the animals to persistent organic pollutants.