Evaluation of the risk of PAHs and dioxins transfer to humans via the dairy ruminant

To evaluate the risk of PAHs and dioxins transfer to humans several studies on dairy ruminant exposure and on intestinal absorption have been conducted. In order to assess PAHs feed-milk transfer, the transfer of three ¹⁴C-labelled PAHs (¹⁴C-phenanthrene, ¹⁴C- pyrene, ¹⁴C-benzo[a]pyrene) and ¹⁴C-2,3,7,8-TCDD has been studied after a single oral ingestion (2.6 × 10⁶ Bq) to lactating goats. Radioactivity associated to the labelled PAHs and 2,3,7,8-TCDD has been detected in milk seven hours after the molecules administration. Cumulated part of ingested radioactivity recovered in milk after five days have reached a similar level after 103 h for ¹⁴C-phenanthrene and ¹⁴C-pyrene (1.5% and 1.9% respectively). ¹⁴C-benzo[a] pyrene did not appear significatively in milk (0.2% of ingested radioactivity). Transfer of ¹⁴C-2,3,7,8-TCDD to milk was higher than for PAHs, reaching 7.8% of ingested radioactivity. The bioavailability of PAHs and dioxins was assessed using two animal models. In one hand, we have characterized the in-vitro transfer of PAHs and dioxin through intestinal barrier using Caco-2 cells cultivated on permeable filters. In the other hand, we have described the specific arterial apparition profile of the studied micropollutants in growing pig. The in-vitro experiment showed that ¹⁴C-pyrene, ¹⁴C-phenanthrene, ¹⁴C-benzo[a]pyrene and ¹⁴C-2,3,7,8-TCDD were able to cross the intestinal barrier. ¹⁴C-phenanthrene was transported 1.1-, 1.8-, and 6.7-folds more than respectively ¹⁴C-pyrene, ¹⁴C-benzo[a]pyrene and ¹⁴C-2,3,7,8-TCDD after 6 h exposure. Regarding arterial apparition profiles, ¹⁴C arterial level from ¹⁴C phenanthrene was about 3 and 10 times more elevated than ¹⁴C level from ^14-C-benzo[a]pyrene and ¹⁴C-TCDD respectively. These results can be related to the intestinal barrier transfer profile of the same molecules. The results presented in this paper contribute to give new insights on evaluation of the risk of PAHs and dioxins transfer to humans via the dairy ruminant. They particularly clarify the way by which organic micropollutants are transferred to milk and to living organisms during digestion and absorption.