Population Exposure to Organic Contaminants and Human Biomonitoring

Sammanfattning: We are surrounded by various chemicals, both naturally occurring and synthetically produced. Some, but not all, chemicals can be hazardous for human health following exposure, especially for vulnerable population groups including children, adolescents, and pregnant women. The increased use and production of chemicals have contributed positively to society in numerous ways, while also resulting in widespread contamination of the environment leading to unwanted human exposure. Knowledge of the magnitude of chemical exposure in populations and potential adverse health effects is insufficient. Human biomonitoring is one approach to estimating internal exposure by analysing defined exposure biomarkers in biological samples, such as blood or urine. It is a reliable measure of the total exposure of a substance from all routes of uptake and enables the assessment of simultaneous exposure to multiple compounds. Human biomonitoring can contribute with important data to improve these methods and the risk management of chemicals on a national and international level. However, human biomonitoring relies on toxicokinetic information of specific chemical compounds to ensure an appropriate sampling protocol that accurately captures the exposure, and for the interpretation of data within risk assessments.This thesis aims to apply human biomonitoring to investigate population exposure and temporal trends of organic contaminants in vulnerable population groups, i.e., adolescents, pregnant women, and infants, in southern Sweden. Furthermore, the included studies provide specific data on selected chemicals regarding toxicokinetics in humans, transplacental transfer efficiency, and whether analytical results of biological samples are affected after long-term storage. Exposure levels and trends were investigated for perfluoroalkyl substances (PFAS) and pesticides in adolescents by collecting blood and urine samples on five different occasions between years 2000 – 2017. We analysed 14 pesticide biomarkers in urine samples, where six were detected in more than 90% of the samples. Exposure to four substances, one of which is banned in Sweden and the EU, slightly increased over time whereas three decreased. The observed trends correspond with pesticide residues detected in domestic and imported cultivated food, and changes in use during the same period. Furthermore, we specifically investigated human elimination kinetics of glyphosate, the most commonly used herbicide globally. The results indicate that the urinary excretion corresponds to 1–6 % of the ingested dose, much less than the previously assumed urinary dose recovery based on animal studies. We assessed PFAS exposure in adolescents over time and prenatal exposure from transplacental transfer in a birth cohort with a wide range of PFAS exposures. In adolescents, PFOA, PFOS, and PFHxS were found in all serum samples but concentrations decreased over time. The decreasing trends of PFAS closely followed the stepwise international phase-out of these substances initiated in year 2002. Prenatal exposure to PFAS was estimated as ratios of umbilical cord serum and maternal serum in a cohort accidentally exposed to high levels through contaminated drinking water. The transfer ratios indicate that the relative transfer efficiency of PFAS is similar in highly exposed women, resulting in higher absolute fetal concentrations and an increased risk of potential health outcomes. The contribution of the thesis to the research field is that it reports novel knowledge of population trends in the exposure of PFAS and pesticides over 17 years, and considers how these trends align with key policy changes, important differences in elimination kinetics of glyphosate between animals and humans, analytical evidence supporting the stability and integrity of biological samples after long-term storage, and that the transplacental transfer of PFAS in highly exposed women result in high absolute fetal exposures. Additionally, the results address important aspects of sample collection procedures, interpretation of biomonitoring data, and the relevance of studying different population groups.