Modelling the fate and behaviour of lipophilic organic contaminants in lactating dairy cows

Meat and dairy products are a key source of human exposure to persistent li pophilic organic contaminants (e.g. PCBs, PCDD/Fs). The primary source of t hese contaminants to beef and dairy cows is the ingestion of contaminated h erbage and supplementary feeds. In turn, herbage is primarily supplied with such contaminants via atmospheric deposition. An in-depth understanding of the transfer of semi-volatile contaminants (SOCs) from air-grass-cow-human is therefore required to quantify and manage this exposure pathway. This p aper is concerned with modelling/predicting milk and tissue contaminant bur dens, given information on measured herbage concentrations. As a result of numerous studies on the transfer of organic contaminants within agricultura l foodchains (e.g. Fries, 1977; Fries, 1995; McLachlan, 1993; Oiling et al. , 1991) generic models are available in the literature. This paper critical ly reviews the commonly used modelling approaches and examines their predic tive capabilities. The influence of natural variability, due to environment al factors and fanning practice, on the contaminant composition of milk is investigated. The paper has implications for regulatory authorities, and ot hers, who may have to take a 'grab' sample of milk, whether from a bulk col lection tank or an individual animal, and then make an assessment on the co ntaminant status of the herd, and the implications of the consumption of th e milk by the general population. (C) 1999 Elsevier Science Inc.. All right s reserved.