Docteur

The last century has been characterized by the increasing presence of synthetic chemicals in human surroundings, with as consequence, the increasing exposure of individuals to a wide variety of chemical substances on a regular basis. The Lancet Commission on Pollution and Health estimated that since synthetic chemicals started to be available for common use at the end of the 1940s, more than 140,000 new chemicals have been produced, including five thousand used globally in massive volume. In parallel, awareness of the adverse effects of pollutant mixtures, possibly more severe than single-chemical exposures, has drawn attention towards the need of multi-residue analytical methods to obtain the most comprehensive information on human chemical exposome. Human biomonitoring, consisting in the measurement of pollutants in biological matrices, provides information that integrates all the possible sources of exposure, and is specific to the subject the sample is collected from. For this purpose, hair appears as a particularly promising matrix to assess chemical exposure thanks to its multiple benefits. Hair enables to detect both parent chemicals and metabolites, it is suitable to investigate exposure to chemicals from different families, and allows the detection of persistent and non-persistent chemicals. Moreover, contrary to fluids such as urine and blood, which only give information on the short-term exposure and present great variability in chemical concentration, hair is representative of wider time windows that can easily cover several months. Children represent the most vulnerable part of the population, and exposure to pollutants at young ages has been associated with severe health effects during childhood, but also during the adult life. Nevertheless, most epidemiological studies investigating exposure to pollutants are still conducted on adults, and data on children remain much more limited.
The present study named “Biomonitoring of children exposure to pollutants based on hair analysis” investigated the relevance of hair analysis for assessing children exposure to pollutants. In this study, 823 hair samples were collected from children and adolescents living in 9 different countries (Luxembourg, France, Spain, Uganda, Indonesia, Ecuador, Suriname, Paraguay and Uruguay), and 117 hair samples were also collected from French adults. All samples were analysed for the detection of 153 organic compounds (140 were pesticides, 4 PCBs, 7 BDEs and 2 bisphenols). Moreover, the hair samples of French adults and children were also analysed for the detection of polycyclic aromatic hydrocarbons (PAH) and their metabolites (n = 62), nicotine, cotinine and metals (n = 36). The results obtained here clearly demonstrated that children living in different geographical areas are simultaneously exposed to multiple chemicals from different chemical classes. Furthermore, the presence of persistent organic pollutants in all children, and not only in adults, suggests that exposure to these chemicals is still ongoing, although these chemicals were banned decades ago. In the sub-group of Luxembourgish children, information collected within questionnaires in parallel to hair sample collection allowed to identify some possible determinant of exposure, such as diet (organic vs conventional), residence area (urban vs countryside), and presence of pets at home. Moreover, results showed higher levels of concentration in younger children, and higher exposure of boys to non-persistent pesticides than girls, which could possibly be attributed to differences in metabolism, behaviour and gender-specific activities. Finally, the study also highlighted high level of similarity in the chemical exposome between children from the same family compared to the rest of the population.
The present study strongly supports the use of hair analysis for assessing exposure to chemical pollutants, and demonstrates the relevance of multi-residue methods to investigate exposome.