Plasma PAH-like AhR Bioactivity, Homocysteine, and Subclinical Vascular and Haematologic Phenotypes in the SPES Biomonitoring Substudy

Receptor-based bioassays measure mixture activity whose relationship with human physiology requires empirical assessment. We examined plasma polycyclic aromatic hydrocarbon (PAH)-like aryl hydrocarbon receptor bioactivity in the selected cross-sectional SPES biomonitoring substudy in Campania, Italy. Out of 598 assay records, 591 had quantified PAH-CALUX results and 7 were below individual limits of quantification (LOQs). Primary models related log2 lipid-normalised benzo[a]pyrene-equivalent bioactivity to homocysteine and recorded seated systolic blood pressure (SBP), adjusting for age, sex, body mass index, current smoking, and sampling cluster fixed effects, with municipality-clustered inference. Holm correction covered the two primary tests; Benjamini–Hochberg correction covered two secondary families. Participants comprised 295 women and 296 men aged 20–50 years from 63 municipalities. Per exposure doubling, homocysteine differed by −0.12% (95% confidence interval [CI], −0.76% to 0.52%; Holm-adjusted p = 0.699) and SBP by −0.37 mmHg (95% CI, −0.80 to 0.06; Holm-adjusted p = 0.183). None of the eighteen secondary outcomes met the within-family false discovery rate threshold. Additional post hoc Akins lipid normalisation and three below-LOQ substitution analyses yielded similar interpretations. These findings describe small estimated contemporaneous associations in a selected population. Uncertainty remains concerning cumulative exposure, temporal variability, and generalisability; equivalence and environmental safety cannot be inferred.