Bioaccumulation of hydrophobic chemicals in agricultural feed chains

The bioaccumulation of polychlorinated biphenyls, dibenzo-p-dioxins, dibenzofurans, and hexachlorobenzene in an air-plant/soil-cow-human food chain was examined using field data collected in southern Germany. The fugacity of many compounds was similar in air, soil, and plants, suggesting near-equilibrium partitioning with somewhat higher fugacities in cows' milk indicative of moderate biomagnification. However, the fugacities of the more involatile, hydrophobic compounds decreased by up to several orders of magnitude from air to plants to cows' milk. This phenomenon, termed biodilution, can be explained by the kinetically limited uptake of less volatile compounds in plants and the reduced absorption of very hydrophobic compounds in cows. Biodilution due to metabolism of certain compounds in covers was also observed. Strong biomagnification was observed in humans as indicated by 20-50 times higher fugacities in human milk compared to cows' milk.