Early life exposure to per-and polyfluoroalkyl substances(PFASs):A critical review

Due to the dynamic developmental processes during pregnancy,infancy,childhood and adolescence,exposure to PFASs is hypothesized to have the most pronounced negative effects during this period.In this review we critically evaluate the current state of the science regarding human early life exposure processes(until 18 years of age)to per-and polyfluoroalkyl substances(PFASs).Efficient placental transfer of perfluoroalkyl acids(PFAAs)results in relatively high prenatal exposure compared with many neutral organic contaminants.The few biomonitoring studies that specifically target infants,toddlers and other children suggest relatively high serum concentrations of perfluorooctane sulfonic acid(PFOS)and perfluorooctanoic acid(PFOA)in early life with peak concentrations occurring sometime before the child reaches 20 months.This peak in serum concentrations is most likely explained by exposure via breastfeeding,ingestion of house dust and/or specific contact events with consumer products leading to high body weight normalized estimated daily intakes(EDIs).Although children have higher EDIs of PFASs than adults,these are not always reflected by higher serum levels of PFASs in children in cross-sectional biomonitoring studies due to the confounding effect of age and birth cohort,and different exposure histories due to production changes.Longitudinal exposure studies measuring internal and external exposure(for multiple pathways and PFASs)at several time points during early life are strongly encouraged to understand temporal changes in exposure of individual children.A better quantitative understanding of early life exposure processes would help to improve the validity of epidemiological studies and allow informed decisions regarding setting of regulatory thresholds and appropriate mitigation actions.

Water-to-air transfer of branched and linear PFOA:Influence of pH,concentration and water type

The volatilisation of perfluorooctanoic acid(PFOA)was measured experimentally at a range of pH values using a previously published laboratory method.Water-to-air transfer was studied for five structural isomers,namely:the linear isomer(n-PFOA)and the four most commonly occurring branched isomers(3-,4-,5-and 6-PFOA).The influence of water concentration and water type on the pH-dependent waterto-air transfer was also investigated for n-PFOA.The water-to-air transfer was studied over the course of 48 h at pH values ranging from 0.2 to 5.5.Under all experimental conditions tested,the volatilisation of PFOA was negligible at pH>2.5.In experiments performed with MilliQ water,volatilisation increased with decreasing water pH.In experiments performed with tap water and lake water,maximum volatilisation was observed at pH 1.The concentration of PFOA in water had no influence on the pH value at which water-to-air transfer was observed(i.e.at pH<2.5)for the concentration range tested(0.1e50 mg/L PFOA in deionised water).Although the percentage of PFOA volatilised was significantly different for the four branched isomers at low pH,volatilisation was not observed above pH 2.5 for any branched isomer suggesting that all PFOA isomers have a low pKa.Overall,these laboratory results demonstrate that volatilisation of any structural isomer of PFOA from water is negligible at environmentally-relevant conditions.It is unlikely that PFOA isomers will be fractionated in the environment as a result of volatilisation because it is a process of negligible environmental relevance.