Environ Int

Background: Chemical biomarker concentrations are driven by complex interactions between chemical use patterns, exposure pathways, and toxicokinetic parameters such as biological half-lives. Criteria to differentiate legacy from current exposures are helpful for interpreting variation in age-based and time trends of chemical exposure and identifying chemicals to which children are highly exposed. A systematic approach is needed to study temporal trends for a wide range of chemicals in the US population. Objectives: Using NHANES data on measured biomarker concentrations for 141 chemicals from 1999–2014, we aim to 1) understand the influence of temporal determinants, in particular time trends, biological half-lives, and restriction dates on age-based trends, 2) systematically define an age-based pattern to identify chemicals with ongoing and high exposure in children, and 3) characterize how age-based trends for six Per- and Polyfluoroalkyl Substances (PFASs) are changing over time. Methods: We performed an integrated analysis of biological half-lives and restriction dates, compared distributions of chemical biomarker concentrations by age group, and then applied a series of regression models to evaluate the linear (βage) and nonlinear (βage2) relationships between age and chemical biomarker levels. Results: For restricted chemicals, a minimum persistence of 1 year in the human body is needed to observe substantial differences between less exposed young population and historically exposed adults. We define a metric (βage2/βage>126.9) that identifies several phthalates, brominated flame retardants, pesticides, and metals such as lead and tungsten to reflect elevated and ongoing exposures in children. While a substantial reduction in children’s exposures was reflected in PFOS and PFOA, levels of PFNA and PFHxS in children were higher in 2013–2014 compared to those in 1999–2000. Conclusions: Integrating a series of regression models with systemized stratified analyses by age group enabled us to define an age-based pattern to identify chemicals that are of higher level in children.

30528102

PMC6903703

Journal Article

CDC Public Access