Evaluation of fetal exposure to environmental pollutants by quantification of volatile organic compounds, pesticides and associated metabolites in meconium
Résumé
Meconium is the earliest stools of newborn. It starts forming from the 13th week of gestation in intestinal contents and accumulates until birth. Usually, it is expelled by the newborn between 24 and 48 hours after birth. The analysis of this complex matrix allows the determination of fetal exposure to xenobiotics over the last six months of pregnancy. The objective of the project “PENEW” (Environment Pregnancy and NEWborn malformations, PHRC 2010 CHU Rennes) is to determine a correlation between the occurrence of malformations and fetal exposure. Analytical developments for the determination in meconium of VOCs (Volatile Organic Compounds) including BTEX (benzene, toluene, ethylbenzene, xylenes) and two chlorinated solvents (trichloroethylene and tetrachloroethylene), BTEX metabolites, pesticides (pyrethroids, organophosphates...) and associated metabolites (dialkylphosphates...) have been performed. These analytical methods were applied to over two hundred meconium samples. Sample preparation of meconium is very complex due to the specific physico-chemical properties of the matrix. VOCs were measured with very low quantification limits (80pg g-(1)) by Head- Space Solid Phase MicroExtraction (HS-SPME) with GC/MS (Gas Chromatography coupled to Mass Spectrometry). The same sample could then be re-used for the analysis of non volatile compounds. A multi-residue method was therefore applied for the quantification of pesticides, metabolites of pesticides and metabolites of VOCs. The sample preparation was composed by two liquid-liquid extractions followed by two successive purifications by SPE (Solid Phase Extraction). The analyses were carried out by LC/MS/MS (Liquid Chromatography with Tandem Mass Spectrometry). Three different LC columns were used: an ion exchange column for the glyphosate analysis; a HILIC column for the analysis of four dialkylphosphates and a reversed-phase column for all the other target compounds. The quantification limits of this multi-residue method were in average of 29ng g-1. All VOCs were determined in meconium samples. The highest concentrations were obtained for benzene and toluene. These two compounds and trichloroethylene were measured in each meconium sample. Tetrachloroethylene, ethylbenzene and xylenes were quantified in few samples. Several metabolites (ocresol, hippuric acid, muconic acid, PGA and S-BMA) were determined in most samples. Several pesticides (dichlorvos, propoxur, malathion, cypermethrine and some metabolites of pesticides: dialkylphosphates) were also occasionally quantified. These two analytical methods based on the use of the same meconium sample enabled the quantification of 33 target molecules. Most of the investigated compounds were determined in the meconium samples. In a further step, a relationship between these results on pollutant exposure and the occurrence of fetal malformations will be studied.