Hammer, A. J.; Kasschau, K. D.; Alexiev, A.; Davis, E. W.; Hoffman, P.; Johnson-Camacho, K.; Anderson, K.; Marriott, L. K.; Shannon, J.; Sharpton, T. J.

Polycyclic aromatic hydrocarbons (PAHs) are pervasive environmental pollutants linked to adverse neurobehavioral outcomes, yet the biological pathways coupling exposure to behavior are poorly defined. The gut microbiome is both sensitive to PAH exposure and a modulator of central nervous system function, suggesting it may mediate how PAH exposure influences neurobehavior. We tested whether PAH exposure, gut microbiome composition, and neurobehavioral function covary in a statewide sample of 34 adults stratified into high-impulsivity/poor-attention (HH) and low-impulsivity/fast-attention (LL) groups. Participants provided fecal samples for 16S rRNA profiling and wore silicone wristbands for 30 days to passively sample PAH exposure. Higher PAH exposure associated with HH group membership in a sex-dependent manner, with the largest elevations among HH males. At the community level, PAH exposure profiles correlated with microbiome dissimilarity, and HH membership associated with increased alpha-diversity and altered community composition relative to LL members. At the taxon level, 21 genera were significantly associated with 14 PAH compounds (FDR < 0.1). No individual genera were significantly associated with neurobehavioral group after multiple testing correction. Nevertheless, cross-referencing PAH-responsive genera (FDR < 0.1) against those with nominal neurobehavioral associations (p < 0.05) identified two candidate genera, Hydrogenoanaerobacterium and Methanobrevibacter, whose abundance covaries with both PAH exposure and neurobehavioral phenotype. Both have been independently linked to cognitive or neurological outcomes in prior work. These findings support a three-way relationship among environmental chemical exposure, gut microbiome composition, and neurobehavioral function, establishing an empirical foundation for testing microbiome-mediated links between PAH exposure and neurobehavioral outcomes.