No abstract

Human activities produce polluting compounds such as persistent organic pollutants (POPs), which may interact with agriculture. These molecules have raised concern about the risk of transfer through the food chain via the animal product. POPs are characterised by a strong persistence in the environment, a high volatility and a lipophilicity, which lead to their accumulation in fat tissues. These compounds are listed in international conventions to organise the information about their potential toxicity for humans and the environment. The aim of this paper is to synthesise current information on dairy ruminant exposure to POPs and the risk of their transfer to milk. Three major groups of POPs have been considered: the polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), the polychlorobiphenyls (PCBs) and the polycyclic aromatic hydrocarbons (PAHs). The results show that contamination of fodder and soil by these compounds is observed when they are exposed to emission sources (steelworks, cementworks, waste incinerators or motorways) compared with remote areas. In general, soil contamination is considered higher than plant contamination. Highest concentrations of POPs in soil may be close to 1000 ng/kg dry matter (DM) for PCDD/Fs, to 10 000 mg/kg DM for PAHs and 100 μg/kg DM for PCBs. The contamination of milk by POPs depends on environmental factors, factors related to the rearing system (fodder and potentially contaminated soil, stage of lactation, medical state of the herd) and of the characteristics of the contaminants. Transfer rates to milk have been established: for PCBs the rate of transfer varies from 5% to 90%, for PCDD/Fs from 1% to 40% and for PAHs from 0.5% to 8%. The differential transfer of the compounds towards milk is related to the hydrophobicity of the pollutants as well as to the metabolic susceptibility of the compounds.

This study investigated milk excretion kinetics of PCBs, tetra-BDE (BDE 47), and penta-BDE (BDE 99) in goats exposed to contaminated soil under controlled conditions. The animals were fed (80 days) with feed containing 5% of contaminated soil. During this exposure period, milk was analyzed weekly. At the end of the experiment the PCBs and PBDEs retained in hepatic and adipose tissues were also determined. The soil-milk carry over rates (CORs) of PCBs ranged from 6 to 62%. This result suggests that a large part of ingested soil-bound PCBs was recovered in milk. Significantly different levels between the congeners were reported in the tissues (fat, liver). BDE 47 and 99 excretions in milk achieved a plateau after 2 weeks of exposure, and their corresponding CORs were about 30%. These two congeners showed a significantly (P < 0.05) lower accumulation in the adipose tissue than the major PCB congeners. The concentrations of BDE 47 and 99 in the liver were the same as PCB concentrations. This result suggests that the low brominated congeners are submitted to the metabolism more extensively than the major PCBs.

Human activities are emitting persistent organic pollutants (POPs) to the environment. These compounds have raised concerns about the risk of transfer through the food chain via animal products. They are characterized by a strong persistence in environmental matrices and a lipophilicity which may lead to their accumulation in fat tissues. In EU Regulations (no. 1881/2006, 1259/2011), maximum acceptable levels for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans (PCDD/Fs), and dioxin-like or nondioxin-like polychlorinated biphenyls (PCBs) in food of animal origin have been set. Transfer rates from contaminated fodder to milk have been established: for PCBs, the rate of transfer varies from 5 to 90% and for PCDD/Fs from 1 to 40%. The differential transfer of the compounds towards milk is related to the hydrophobicity of the pollutants and to their metabolic susceptibility. According to numerous authors, soil is the major reservoir for POPs, and its involuntary ingestion by farm animals reared outdoors may be the main cause of animal product contamination (meat, milk, or eggs). Recent studies seem to indicate that soil is a real risk matrix in terms of transfer of pollutants to the food chain. A POP crisis management is extremely difficult, since it impacts many farmers located in the contaminated area. The question arising is to know if livestock contaminated by POPs may be decontaminated and further used for their initial purpose. Recent data demonstrate that the decontamination process appear feasible and depends on initial level of contamination or the physiological status of the animals.