Exposure assessment of prepubertal children to steroid endocrine disrupters 1. Analytical strategy for estrogens measurement in plasma at ultra-trace level.

Global concern has been raised in recent years over adverse effects that may result from exposure to chemicals that may interfere with the endocrine system. A specific question is related to low-dose effects and long-term exposure consequences, especially for critical populations (foetus, new born, prepubertal children). In this context, we decided to focus our attention on steroid hormones as they are the most potent endocrine disrupters. Our general goal is to investigate whether the steroid intake through food may represent a risk for prepubertal children, from an endocrine disruption point of view, especially with regard to the corresponding endogenous production level in this target population. As a starting point, it was estimated that a (re)-evaluation of the endogenous production of natural estrogens for this population was necessary, on the basis of a very sensitive and specific confirmatory measurement technique (gas chromatography-tandem mass spectrometry or gas chromatography-high resolution mass spectrometry). Thus, a new ultra-sensitive approach for steroid trace measurement in biological samples was developed, which was mainly based on a specific derivatisation (pentafluorobenzyl derivative) and negative chemical ionisation (NCI). Preliminary results obtained by applying this method on plasma samples from healthy prepubertal children demonstrated that estradiol endogenous level in prepubertal children is unsurprisingly very low. Estrone was determined in almost all samples at concentration in the 2-70 ng L(-1) range while 17alpha and 17beta estradiol were quantified in only few samples at concentrations ranging from 2 to 6 ng L(-1). Exogenous contributions of estrogens will therefore constitute a relatively higher proportion of sex hormone activity in the immature child.