Sheep milk as a potential indicator of environmental exposure to dioxin-like polychlorinated biphenyls (dl-PCBs)

Dioxin-like polychlorinated biphenyls are lipophilic persistent organic pollutants which accumulate in the fat tissue of animals. Moreover, in mammals, these contaminants are secreted into milk during lactation periods. The contamination level of milk is closely related to the animal dl-PCBs exposure through diet, inhalation and dermal contact. The study of the relationship between the environment in which the animals live and the milk contamination level is a key component in assessing the presence of pollutants in dairy products. In this paper, soil was selected as a reliable matrix of environmental pollution with dl-PCBs as it reflects as well the possible contamination of vegetation and air in the areas where sheep graze and live. However, dl-PCBs analysis could be problematic due to the high cost. To overcome this problem, the approach of this study was focused on using GIS and geostatistics to integrate data from different research institutions, aiming to assess the relationship between milk and soil contaminated with dl-PCBs. Therefore, samples of soil and sheep milk collected in Campania (Italy) during 2008 monitoring plans were introduced in a GIS. The relationship between the two variables showed heteroscedasticity, and the global regression technique OLS indicated a R2 of 0.24. To improve the OLS results, the altitude was integrated in the GIS considering that this variable can influence PCBs contamination. The results showed that altitude is strongly related with soil contamination but was not strongly related with milk contamination. Thus, analyzing the relationship between milk and soil contamination dividing data in three different groups of altitude ranges, the R2 values were higher. Furthermore, this correlation changes with the altitude, becoming weaker with higher altitude. These results show the possibility to use sheep milk as indicator of PCBs contamination at least from sheep bred under 300 m of altitude.