The contamination of milkfat with persistent, often aromatic chlorinated hydrocarbons from the group of the pesticide residues (hexachlorobenzene, hexachlorocyclohexane, dieldrin, total DDT), of the polychlorinated biphenyls (according to the Ordinance on maximum limit for toxic elements), and of the polychlorinated dibenzodioxins and dibenzofurans was studied in 2001 all over in Schleswig-Holstein in 271 tanker bulk milk samples and 26 fat containing milk products (cream, yoghurt, whole milk powder (as well as in 31 butter samples on dioxin/furans)). The contamination of the milkfat occurred on an exclusively secretory basis as a result of a corresponding feed contamination. In a pure air region like Schleswig-Holstein, it is expected that these values will be very low in feeds (produced on the farm), and also in the milkfat. Thus, as regards milkfat, the findings for pesticide residues in tanker bulk milk were 2.7; 4.7; 0.8; 1.4; 0.6 and 2.4 mg/kg for HCB, alpha-HCH, beta-HCH, gamma-HCH, dieldrin, and total DDT (arithmetic mean values). In the group of the polychlorinated biphenyls the highly chlorinated congeners 138, 153 and 180 showed the following mean values: 1.9; 2.5 and 1.2 mg/kg fat. The investigation of the 17 laterally substituted dibenzodioxins and dibenzofurans was summed up for tanker bulk milk and butterfat (n = 62) and yielded a mean value of 0.2 pg WHO-TEQ (PCDD/F)/g fat in a range between 0.12 and 0.33 pg/g. Compared with the valid maximum values for pesticide residues (list B of the Ordinance on maximum limit for residues) and polychlorinated biphenyls (Ordinance on maximum limit for toxic elements) the corresponding upper bound values are only replenished to a marginal percentage, even under consideration of the respective maximum values. In Germany and in the other European countries there still doesn't exist a corresponding threshold value for PCDD/F as regards consumer protection. If the contamination degrees for the three investigated groups of harmful substances in 40 g milkfat are considered as the average, daily consumed quantity of milkfat, and are put in relation with the threshold doses of admissible or tolerable daily intake quantities, this results, even under the assumption of the maximum value, into extremely low contamination percentages for the pesticide residues. This is also true for the polychlorinated biphenyls. The situation is a little bit more complicated for the polychlorinated dibenzodioxins and dibenzofurans, for which the actually applicable threshold value of the tolerable intake quantity also includes other toxic equivalents with dioxin-like reactions, e.g. the coplanar (dioxin-like) PCB congeners. Furthermore, there exists a margin for the above mentioned tolerable, limited intake by factor 4, so that for pragmatic and also for health prevention reasons a threshold value of 1 pg dioxin-like toxic equivalent per kg body weight and day is referred to. Because of a supposed equal level between toxic equivalents from "pure" dioxins and furans, and the coplanar PCB congeners, the aforementioned value is reduced to 0.5 pg/kg body weight and day. Under this assumption and on the background of the average contamination observed in Schleswig-Holstein, 40 g milkfat per day contribute with 23% to this threshold dose. If the maximum value is referred to, it will make up 37.7%, so that a considerable margin still remains for other foods from animal origin. On the whole, the presented figures for the contamination of milkfat with persistent organochoride compounds prove that milk production in a pure air area largely harmonizes with the threshold values fixed by the consumer protection organizations.
