Carry-over of environmental contaminants into milk and food hygiene assessment/management

Together with the large amount of major and trace nutrients in the feed ration of the dairy cow, a small and widely varying amount of undesired chemical Substances from the environment is ingested by the animal and in traces excreted with the milk. This mechanism, called carry-over, depends on the chemical nature of the compounds in question and their principal ability to pass the blood-milk-barrier. The practical importance of carry-over is found in the field of food safety, linking the environment, represented by fodder, with milk. with regard to undesirable substances. The substances dealt with here are polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins and furans (PCDD/Fs), lead and cadmium as examples of toxic trace elements, and mycotoxins as a group of non-anthropogenic organic chemicals from the environment. From the abundance of civilization and/or household chemicals, the ubiquitous phthalic acid ester DEHP and also nitro musk fragrances are occasionally mentioned. For all these substances the environment, including the direct farm environment of the cow, is either the original source, a secondary catchment or the habitat for toxin-producing moulds. The carry-over rates observed are relatively high to nearly quantitative in the case of the PCBs (up to 80%) and some PCDD/F-congeners (up to 60%) or low (2-3%) in the case of aflatoxin B1, practically the only mycotoxin known until now, which shows a significant carry-over into milk. More-or-less negligible carry-over rates in the order of markedly less than 0.1%, show lead and cadmium as their ions. The risk-assessment procedure involves the combination of hazard identification, assessment of the dose-response relationship in biological test systems, the exposure assessment, meaning the role of food for intake by human consumers, and a preliminary risk characterization. The second step is the mainly administrative risk management by public organs with the intention of minimizing food-borne toxicological risk. It is obvious that the carry-over rate plays the major role in this context, being the link between thresholds in animal feed and in milk. In the food industry the HACCP concept is a very effective tool to control and eliminate hazards during production. In feed production this concept would be restricted to industrial feed manufacturing. It is not feasible for the bulk of animal feed cultivated and handled on the farm. Here, carefully elaborated, food/feed-hygiene focused codes of practice for good animal feeding, dairy farming, farming practice and manufacturing are the safety tools for appropriate non-governmental risk management.