Oral microbiome alterations and their association with long-term heavy metal exposure and early health effects.

Background: Long-term heavy metal exposure poses health risks, and non-invasive biomarkers for early detection are needed. Objective: This study investigated whether oral microbiome alterations can serve as a non-invasive indicator of long-term HMs exposure and associated early biological effects. Design: Soil, buccal mucosa, blood, and urine samples were collected from contaminated (CA) and uncontaminated (UA) areas. Soil contamination was assessed, and internal biomarkers were measured. Oral bacterial diversity was analyzed using metagenomic sequencing. Results: Severe Cd and Pb contamination was found in CA soil. Participants in CA had elevated internal Cd levels, renal impairment, and immune alterations. Oral microbiome analysis revealed decreased alpha diversity, reduced network complexity, and a shift from beneficial to pathogenic keystone taxa in CA. Functional analysis showed enrichment of stress-response pathways, suppression of metabolic pathways, and increased pathways linked to human diseases. Specific bacterial taxa correlated with internal biomarker levels. Conclusions: There is a close association between long-term HMs exposure and reproducible, multi-faceted shifts in the oral microbiome. The oral microbiome may represent a promising, non-invasive biomarker for assessing environmental exposure and its early biological impacts.