Hematological alterations by gender and age linked to mercury exposure in residents of the Colombian Atrato River artisanal gold mining region

The Atrato River basin in western Colombia, one of the most biodiverse regions globally, faces severe mercury (Hg) contamination from artisanal gold mining. This study assessed the hematological effects of Hg exposure in 601 residents (aged 15-89 years) from four localities with different exposure levels. Blood mercury concentrations (HgB) were used to classify participants into high (HHgB >5.0 µg/L; n = 507) and low (LHgB <5.0 µg/L; n = 94) exposure groups. Alarmingly, the median HgB was 14.95 µg/L, and 84.3 % of samples exceeded the safety threshold of 5.0 µg/L. Males consistently showed higher HgB levels than females, particularly in adult and older age groups. Significant hematological alterations were observed in associations with Hg exposure. A considerable proportion of HHgB participants showed anemia: 14.7 % of young males and 21.2 % of young females had low hemoglobin; 6.9 % of adult males and 19.1 % of adult females had reduced hematocrit. Gender- and age-based differences were detected in multiple hematological parameters (HGB, HCT, RBC, MCHC, LYMPH, and PLT) measured using an Abbott Cell-Dyn Sapphire Analyzer, showing distinct patterns between HHgB and LHgB groups. Positive correlations were found between HgB and HGB or MCV in young males, and between HgB and neutrophils in young females with neutropenia, suggesting Hg-related disruption of red and white blood cell profiles. Comparisons between exposure groups also revealed differences in basophils, monocytes, and lymphocytes, especially among adults and olders. Despite regulations banning mercury use, continued exposure remains a major public health concern. These findings highlight the urgent need for targeted policies to strengthen enforcement of mercury regulations, increase monitoring, and implement community-based health interventions in gold mining regions.