Per- and Polyfluoroalkyl Substances in Urine Samples from Eight-Year-Old Children Living in Northwest Spain

Per- and polyfluoroalkyl substances (PFAS) are synthetics prized for their chemical stability and functionality. Legacy PFAS such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) have been phased out due to their persistence and toxicity. This study assessed exposure to both legacy and emerging PFAS in 281 urine samples from 8-year-old children participating in the (<i>Infancia y Medio Ambiente</i>) INMA Asturias birth cohort (northwest Spain), a region with a strong industrial background. Dietary and household information was collected via questionnaires, and urine samples were analysed using ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution mass spectrometry (HRMS) with full-scan acquisition in independent all-ion fragmentation mode. A suspected screening approach was applied to discover previously unreported PFAS and expand the detectable chemical profile, complemented by targeted analysis of 29 compounds selected for their persistence and regulatory relevance. Among them, 17 compounds were confirmed and quantified. The combined targeted and suspect-screening approach also identified novel PFAS, including fluorotelomer carboxylic acids, demonstrating the value of LC-HRMS for detecting unregulated compounds. Emerging PFAS showed the highest detection frequencies and concentrations: trifluoroacetic acid (TFA) and hexafluoropropylene oxide dimer acid (HFPO-DA, GenX) were detected in 63% and 27% of samples, respectively, with GenX reaching 10.1 ng/mL, whereas PFOA and PFOS were detected less frequently (8.5% and 3.2%) and at concentrations below 1 ng/mL, highlighting the need for epidemiological studies to achieve comprehensive PFAS exposure assessments. Associations with dietary habit exposure estimates point to dairy, protein-rich foods, vegetables, and drinking water as the main contributors.