Association between blood mercury levels and estimated glomerular filtration rate in a Spanish population with high fish consumption: A cross-sectional study.

BACKGROUND The impact of mercury (Hg) on the estimated glomerular filtration rate (eGFR) remains inconsistent across epidemiological studies, often due to low exposure levels or the presence of dietary factors such as selenium (Se). This study evaluates the independent association between blood Hg and eGFR in a population with high dietary fish intake.

METHODS A cross-sectional study was conducted on 373 healthcare workers in Madrid, Spain. Blood levels of Hg were measured by cold vapour atomic absorption spectrometry and Cd, Pb and Se by electrothermal atomization atomic absorption spectrometry. eGFR was calculated using the CKD-EPI formula. Participants were categorized by the median blood Hg level (8 µg/L), a threshold previously linked to cardiovascular risk.

RESULTS Participants had a mean age of 47.3 ± 10.9 years, and a mean estimated glomerular filtration rate (eGFR) of 78.9 ± 11.8 mL/min/1.73 m²; 16.1% were male. Median blood mercury concentration was 8.0 µg/L (IQR: 5.2-11.6); median cadmium and lead levels were 0.29 µg/L (IQR: 0.18-0.50) and 1.7 µg/dL (IQR: 1.0-2.8), respectively, while mean selenium was 79.4 ± 11.7 µg/L. In linear regression analyses, blood mercury levels > 8 µg/L were associated with lower eGFR in the unadjusted model (β = -3.78; 95% CI: -6.17 to -1.39; p = 0.002) and after adjustment for age, sex, and vascular risk factors (β = -3.08; 95% CI: -5.45 to -0.72; p = 0.011). This association remained significant after further adjustment for co-exposure to cadmium, lead and selenium (β = -2.62; 95% CI: -5.02 to -0.21; p = 0.033).

CONCLUSIONS In a population of healthcare workers with high fish consumption, blood mercury levels above 8 µg/L are associated with a modest reduction in eGFR. These findings suggest that Hg may exert a subtle influence on renal filtration independent of other common nephrotoxic metals and dietary elements like selenium.