Determination of naturally occurring oestrogens and androgens in retail samples of milk and eggs

The occurrence of the main steroid hormones (oestrone, 17 alpha-oestradiol, 17 beta-oestradiol, 17 alpha-testosterone, 17 beta-testosterone, dehydroepiandrosterone, 4-androstenedione), especially in milk and eggs, was investigated. An analytical method based on GC-MS/MS was developed for steroid measurement at an ultra-trace level in food products. The limits of detection for oestrogens were about 5 and 30 ng kg(-1) in milk and eggs, respectively. For androgens, the limits of detection were around 10 and 50 ng kg(-1) in milk and eggs, respectively. The method was applied to milk and egg samples collected in a French supermarket. In milk, oestrone was found at levels between 100 and 300 ng l(-1), while 17 beta-oestradiol levels were estimated to be near 20 ngl(-1). 17 alpha-testosterone was found to be from 50 ngl(-1) in skimmed milk to 85 ng l(-1) in whole milk. In egg samples, oestrone and 17 beta-oestradiol were found at 1.5 and 0.9 mu g kg(-1), respectively, while 17 beta-oestradiol was found to be in lower concentrations (i.e. around 0.55 mu g kg(-1)). Regarding androgens, 17 alpha- and 17 beta-testosterone were estimated at 1.9 and 1.3 mu g kg(-1), respectively. These results represent a first attempt to estimate the food exposure to steroid hormones. In the future, the collection of additional data should permit the comparison between this exogenous dietary intake and the daily endogenous production in pre-pubertal children as a basis of risk assessment regarding endocrine disruption linked to these molecules for this critical population.