Serum Levels of Per- and Polyfluoroalkyl Substances in Adults Aged 18 and Older in Relation to the Length of Residency in United States.

Immigrants in the United States may experience varying levels of exposure to perfluoroalkyl substances (PFAS) depending on their duration of residency and their region of origin. PFAS are persistent environmental pollutants linked to adverse health outcomes, yet little is known about exposure levels among immigrant populations. This cross-sectional study utilized data from the National Health and Nutrition Examination Survey (NHANES) 2003-2018 to assess serum PFAS concentrations among adults by length of U.S. residency and race/ethnicity (used as proxy for origin). Several PFAS compounds were analyzed using ANCOVA and general linear models. U.S.-born adults represented 74.9% (n = 8,272) of the sample. Overall, PFAS levels increased with time in the U.S., converging towards levels observed in U.S.-born individuals-, consistent with the long biological half-lives of certain PFAS compounds. Significant differences in ∑PFAS were found for immigrants residing less than 5 years (geometric mean ratio [GMR]: 0.73, 95% CI: 0.64-0.84, P < 0.0001), with smaller differences in those residing 5-10 years (GMR: 0.84, 95% CI: 0.77-0.91, P < 0.0001) or 10-15 years (GMR: 0.84, 95% CI: 0.77-0.93, P = 0.0004), compared to U.S.-born. The pace of convergence varied by race/ethnicity, reflecting both environmental exposure in the U.S. and likely differences in exposure prior to migration. These results emphasize the need to consider duration of residency and background when evaluating chemical exposure disparities. The study highlights the need for public health interventions to address PFAS exposure among immigrants, especially those newly arrived, considering their potential differential exposure risks.