Residential proximity to transport facilities as urban determinants of individual-level per- and poly-fluoroalkyl substance (PFAS) exposures: Analysis of two longitudinal cohorts in Singapore

Abstract Background Policy-relevant spatial determinants of human exposure to Perfluoroalkyl Substances (PFAS), a broad class of persistent environmental contaminants affecting pregnancy and child development, remain poorly understood because of the diversity of exposure sources. This is especially true for modern, dense urban settings, which contain less well-studied built environment-related sources, including transportation-related ground and airborne contamination. Methods We link high-resolution spatiotemporal urban land use data to longitudinal residential histories to assess determinants of individual-level blood plasma PFAS exposures in two geographically- and demographically- diverse cohorts of pregnant women in urban Singapore (n = 784 in 2009–2011; n = 384 in 2015–2017). Longitudinal repeated measures allow us to rule out socio-behavioral factors (e.g., residential segregation) as alternative explanations. Actual land use occupancies were ground-truthed through automated extraction of Google Street View data. Findings Adjusting for known predictors and within-neighborhood unobserved spatial heterogeneity, a standard deviation (SD) increase ( $$\sim$$ 10,000m $$^2$$ ) in transport facility exposure was linked to 0.11 (1.78 ng/mL), 0.16, 0.11 SD increases in residents’ perfluorobutane sulfonic acid (PFBS), perfluorobutanoic acid (PFBA), and perfluorononanoic acid (PFNA) concentrations, respectively, in the 2009 cohort. Dose-response analyses suggested that associations strengthened when transport facilities exceeded 10,000 m $$^2$$ , with residents living near $$\ge$$ 12,000 m $$^2$$ exhibiting 7.3 ng/mL higher plasma PFBS (p = 0.04), consistent with footprints from large bus depots rather than smaller petrol kiosks. Associations with different PFAS congeners were replicated in the 2015 cohort. No other land use type showed similarly consistent findings. Interpretations Transport facilities are prevalent near residences in urban settings and may be potential sources of PFAS emissions from automotive-related lubricants, parts, and materials. Our findings that exposure was robustly associated with individual-level concentration, over and above behavioral and other factors, highlight the importance of monitoring these and other urban sources of exposure.