Correlation between gold and mercury in human blood among individuals in northwestern Tanzania

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Introduction: Mercury is a highly toxic metal of major global health concern, with exposure disproportionately affecting low- and middle-income countries (LMICs) where artisanal and small-scale gold mining (ASGM) is common. While mercury exposure has been well documented among mining populations, less is known about exposure in general urban populations. Materials and methods: We analyzed baseline data from 1000 adults enrolled in the Mwanza HIV and Cardiovascular Disease cohort (2015–2019) in northern Tanzania. Blood total mercury (T-Hg) and total gold (T-Au) concentrations were measured from dried blood spots using inductively coupled plasma mass spectrometry. Associations between T-Hg and T-Au concentrations were evaluated using Spearman’s rank correlation. Associations between a priori-selected covariates and T-Au concentrations were assessed using multivariable bootstrap linear regression models with 1000 resampling iterations. Results: All participants had detectable blood mercury levels, with a median T-Hg concentration of 5.02 μg/l, and 7.2% had levels exceeding the World Health Organization toxic threshold of ≥20 μg/l. Detectable T-Au was observed in approximately 60% of participants, with a median T-Au concentration of 0.09 μg/l. In bootstrap multivariable regression analyses, HIV infection was associated with higher T-Au concentrations (median β = 0.28; 95% bootstrap CI 0.12–0.51). T-Hg and T-Au concentrations were moderately positively correlated in Spearman’s rank correlation (ρ = 0.45; p < 0.001). After multivariable adjustment, T-Hg remained positively associated with T-Au concentrations (median β = 0.39; 95% bootstrap CI 0.22–0.58). Conclusions: We found that T-Hg and T-Au were detectable in a general population living near an ASGM site, and associated with each other, suggesting a common source of exposure. Improved characterization of exposure routes is critical for informing targeted interventions to reduce mercury-related health risks in Tanzanian communities.