Background: Polycyclic aromatic hydrocarbons (PAHs) are of environmental and public health concerns and contribute to adverse skin attributes such as premature skin aging and pigmentary disorder. However, little information is available on the potential roles of chronic urban PAH pollutant exposure on the cutaneous microbiota. Given the roles of the skin microbiota have on healthy and undesirable skin phenotypes and the relationships between PAHs and skin properties, we hypothesize that exposure of PAHs may be associated with changes in the cutaneous microbiota. In this study, the skin microbiota of over two hundred Chinese individuals from two cities in China with varying exposure levels of PAHs were characterized by bacterial and fungal amplicon and shotgun metagenomics sequencing. Results: Skin site and city were strong parameters in changing microbial communities and their assembly processes. Reductions of bacterial-fungal microbial network structural integrity and stability were associated with skin conditions (acne and dandruff). Multivariate analysis revealed associations between abundances of Propionibacterium and Malassezia with host properties and pollutant exposure levels. Shannon diversity increase was correlated to exposure levels of PAHs in a dose-dependent manner. Shotgun metagenomics analysis of samples (n = 32) from individuals of the lowest and highest exposure levels of PAHs further highlighted associations between the PAHs quantified and decrease in abundances of skin commensals and increase in oral bacteria. Functional analysis identified associations between levels of PAHs and abundance of microbial genes of metabolic and other pathways with potential importance in host-microbe interactions as well as degradation of aromatic compounds. Conclusions: The results in this study demonstrated the changes in composition and functional capacities of the cutaneous microbiota associated with chronic exposure levels of PAHs. Findings from this study will aid the development of strategies to harness the microbiota in protecting the skin against pollutants.

Urine and plasma have been used to date for the biomonitoring of exposure to pollutants and are still the preferred fluids for this purpose; however, these fluids mainly provide information on the short term and may present a high level of variability regarding pesticide concentrations, especially for nonpersistent compounds. Hair analysis may provide information about chronic exposure that is averaged over several months; therefore, this method has been proposed as an alternative to solely relying on these fluids. Although the possibility of detecting pesticides in hair has been demonstrated over the past few years, the unknown linkage between exposure and pesticides concentration in hair has limited the recognition of this matrix as a relevant tool for assessing human exposure. Based on a rat model in which there was controlled exposure to a mixture of pesticides composed of lindane, β-hexachlorocyclohexane, β-endosulfan, p,p′-DDT, p,p′-DDE, dieldrin, pentachlorophenol, diazinon, chlorpyrifos, cyhalothrin, permethrin, cypermethrin, propiconazole, fipronil, oxadiazon, diflufenican, trifluralin, carbofuran, and propoxur, the current work demonstrates the association between exposure intensity and resulting pesticide concentration in hair. We also compared the results obtained from a hair analysis to urine and plasma collected from the same rats. Hair, blood, and urine were collected from rats submitted to 90-day exposure by gavage to the aforementioned mixture of common pesticides at different levels. We observed a linear relationship between exposure intensity and the concentration of pesticides in the rats’ hair (R _Pearson 0.453–0.978, p < 0.01). A comparison with results from urine and plasma samples demonstrated the relevance of hair analysis and, for many chemicals, its superiority over using fluids for differentiating animals from different groups and for re-attributing animals to their correct groups of exposure based on pesticide concentrations in the matrix. Therefore, this study strongly supports hair analysis as a reliable tool to be used during epidemiological studies to investigate exposure-associated adverse health effects.

The quantitative assessment of human exposure to contaminants such as pesticides is a crucial step in the characterization of exposure-associated risk. For this purpose, biomonitoring is often privileged as it presents the advantage of integrating all the possible sources and routes of exposure and of being representative of the internal dose resulting from exposure. Although biological fluids such as urine and blood have been used to date for this purpose, increasing interest has also been observed over the past decade for hair analysis. The present work aimed at comparing the information obtained from the analysis of urine versus hair regarding exposure to pesticides in a pilot cohort of pregnant women. In ninety-three pregnant women included in the pilot of the French cohort ELFE, one urine and one hair sample were collected simultaneously from each subject at the maternity. Samples were analyzed using GC-MS/MS analytical methods allowing for the detection of both parent pesticides and metabolites, and designed to be as similar as possible between urine and hair for reliable inter-matrix comparison. Fifty-two biomarkers of exposure were targeted, including parents and metabolites of organochlorines, organophosphates, pyrethroids, carbamates, phenylpyrazoles and other pesticides. The number of different compounds detected ranged from 16 to 27 (median = 22) in hair, and from 3 to 22 (median = 12) in urine. In hair, 24 compounds were found in > 40% of the individuals, whereas only 12 compounds presented the same frequency of detection in urine. Among the chemicals detected in > 80% of both hair and urine samples, only one (pentachlorophenol) showed a signification correlation between hair and urine concentrations. The present results highlight the multiple exposure of the pregnant women included in this cohort and suggest that hair provides more comprehensive information on pesticide exposure than urine analysis. This study thus supports the relevance of hair analysis in future epidemiological studies investigating association between exposure and adverse health effects.

Children represent one of the most vulnerable parts of the population regarding the effects of pollutants exposure on health. In this study, hair samples were collected between October 2013 and August 2015 from 142 French children originating from different geographical areas (urban and rural) and analysed with a GC/MS-MS method, allowing for the detection of 55 biomarkers for pesticides and metabolites both persistent and non-persistent from different families, including: organochlorines, organophosphates, pyrethroids, azoles, dinitroanilines, oxadiazines, phenylpyrazoles and carboxamidas; 4 polychlorobiphenyls (PCBs) and 5 polybromodiphenylethers (PBDEs). The number of compounds detected in each sample ranged from 9 up to 37 (21 on average), which clearly highlighted the cumulative exposure of the children. The results also showed a wide range of concentration of the pollutants in hair (often more than 100 times higher in the most exposed child compared to the less exposed), suggesting significant disparities in the exposure level, even in children living in the same area. In addition to the detection of currently used chemicals, the presence of persistent organic pollutants (POPs) in children also suggests that the French population is still exposed to POPs nowadays. PCP, DEP, PNP, 3Me4NP, trans-Cl2CA, 3PBA, fipronil and fipronil sulfone, presented statistically significant higher concentration in the hair of boys compared to girls. PCP, PNP and 3Me4NP presented statistically significant higher concentration in younger children. Finally, this study also suggests that local environmental contamination would not be the main source of exposure, and that individual specificities (habits, diet…) would be the main contributors to the exposure to the pollutants analysed here. The present study strongly supports the relevance of hair for the biomonitoring of exposure and provides the first values of organic pollutant concentration in the hair of French children.