Biocide contamination of domestic greywater: an indicator of uses by inhabitants

International audience

English. Biocidal substances are used in several areas of the domestic environment (pharmaceuticals and personal care products, pesticides, cleaning products, etc.) but they can be a threat to environmental and human health. It is therefore essential to characterize contamination by biocidal substances in domestic greywater, which is too poorly documented. This will enable us to estimate the contribution of domestic activities to the biocidal substance discharges into the receiving environment. The aim of this research is (i) to conduct a survey on inhabitant habits in terms of product used and practices; (ii) to characterize domestic greywater contamination by analysing 29 prioritized biocidal substances; and (iii) to compare both approaches in order to assess the effect of inhabitant habits on greywater contamination. To carry out this study, greywater samples were taken from seven dwellings in the Paris conurbation (four washing machine samples, six manual dishwashing samples, five floor cleaning samples, four shower samples and one sink sample). 29 biocidal substances were quantified by liquid chromatography and tandem mass spectrometry. Information about the formulation of products used by participants was collected in order to establish a link between uses and contamination. 3 investigations were conducted in supermarkets to complete information about formulation and improve knowledge on marketed products. 26 molecules were quantified in at least one of the 20 samples. Four substances have a quantification frequency higher than 75%: 3 quaternary ammonium compounds (QACs) and 1 isothiazolinone. The substances quantified vary from one dwelling to another, but much more so according to the type of greywater used. Floor greywaters are the most concentrated when manual dishwashing and shower are the less concentrated. The highest concentrations were measured for QACs (benzalkonium chloride C16 > 20,000 ng/L) in floor greywater. Isothiazolinone and QAC concentrations are highest in greywater in line with the results of the market and inhabitant’s surveys, which highlights the predominance of these molecules. The maximum concentration of cypermethrin measured exceeds 6,000 ng/L and can be explained by the presence of carpeting in corridors outside the dwelling. This new database gives us an idea of biocidal contamination in dwellings. The final aim is to estimate the daily tonnages of biocidal substances emitted from domestic environments via greywater.