Hematological Parameters and Mercury Exposure in Children Living Along Gold-Mining-Impacted Rivers in the Mojana Region, Colombia

Mercury (Hg) exposure is a key determinant of human health, arising from environmental, occupational, and domestic sources, as well as the consumption of contaminated food, particularly fish. Due to their developmental stage and heightened susceptibility, children are especially vulnerable. This study evaluated Hg contamination in a high-risk pediatric population affected by local economic activities such as small-scale gold mining, agriculture, and fishing. The objective was to determine whether exposure to this toxic metal was associated with alterations in hematological biomarkers, analyzing potential correlations with total Hg (T-Hg) levels in the hair and blood of 282 children aged 6 to 12 years in the Mojana Bolivarense (Colombia). The mean T-Hg concentration in hair was 0.88 µg/g in Magangue, 1.55 µg/g in Achi, and 0.26 µg/g in Arjona. A total of 35.0% and 44.4% of the examined minors from Magangue and Achi, respectively, exceeded the international threshold for hair Hg (1 µg/g). Likewise, blood T-Hg concentrations surpassed the recommended safety level (5 μg/L) in 39.4% of children from Achi and 0.8% from Magangue, while in Arjona, all values remained below this threshold. The geometric mean (GM) values of the hair-to-blood Hg ratio varied across locations. Spearman correlations revealed a very strong positive association between blood and hair T-Hg levels in Achi (ρ = 0.801; p < 0.01), a moderate correlation in Magangue (ρ = 0.325; p < 0.01), and some significant links with hematological parameters. Multiple linear regression analysis indicated a positive association between blood T-Hg concentration and white blood cell count (β = 0.053; p = 0.021) and granulocytes (β = 0.086; p = 0.011), as well as an inverse correlation with lymphocyte percentage (β = - 0.353; p = 0.036). These findings suggest that Hg exposure may influence inflammatory and immunosuppressive processes, posing a potential health risk to vulnerable populations, particularly young individuals.