Milk and urine excretion of polycyclic aromatic hydrocarbons and their hydroxylated metabolites after a single oral administration in ruminants

The aim of this study was to establish the transfer of phenanthrene, pyrene, and benzo[a]pyrene and their major hydroxylated metabolites to milk and to urine after a single oral administration (100 mg per animal of each compound) in 4 lactating goats. Detection and identification of the analytes (native compounds, 1-OH pyrene, 3-OH phenanthrene, 3-OH benzo [a]pyrene) were achieved using gas chromatography-mass spectrometry. Benzo [a] pyrene, phenanthrene, and pyrene were rapidly detected in the plasma stream, whereas 1-OH pyrene and 3-OH phenanthrene appeared later in plasma. These data suggest that pyrene and phenanthrene are progressively metabolized within the organism. Recovery rates of pyrene and phenanthrene in milk over a 24-h period appeared to be very low (0.014 and 0.006%, respectively), whereas the transfer rates of their corresponding metabolites were significantly higher: 0.44% for 1-OH pyrene and 0.073% for 3-OH phenanthrene. Recovery rates in urine were found to be higher (1 to 10 times) than recovery rates in milk. The 1-OH pyrene was found to be the main metabolite in urine as well as in milk. Thus, as has been established for humans, 1-OH pyrene could be considered as a marker of ruminant exposure to polycyclic aromatic hydrocarbons. Because 1-OH pyrene and 3-OH phenanthrene were measured in milk (unlike their corresponding native molecules), metabolites of polycyclic aromatic hydrocarbons should be taken into consideration when evaluating the safety of milk. Benzo [a] pyrene and 3-OH benzo [a]pyrene were (less than 0.005%) transferred to milk and urine in very slight amounts. This very limited transfer rate of both compounds suggests a low risk of exposure by humans to benzo [a] pyrene or its major metabolite from milk or milk products.