Mercury exposure and omega-3 fatty acid intake in relation to renal function in the US population

It remains unclear whether exposure to low-level mercury (Hg) is associated with impaired renal function, and whether omega-3 fatty acid (FA) intake could affect the association of interest. The current study examined the association of blood Hg and omega-3 FAs with renal function using data from 1046 subjects aged 40 or above from the 2003-2004 National Health and Nutrition Examination Survey. Kidney function was assessed by estimated glomerular filtration rate (eGFR) and occurrence of albuminuria. Logistic regression analyses were applied to assess the association of interest with confounding variable adjustment. The analyses indicated that blood Hg was associated with reduced eGFR (<60mL/min/1.73m(2)) in a dose-response fashion (p<0.05). The association was particularly apparent with adjustment for blood omega-3 FA levels. The adjusted odds ratio for having reduced eGFR was 2.94 (95% confidence interval=1.04-8.33) in the highest tertile of blood Hg as compared with the lowest tertile. There was no significant association between Hg exposure and albuminuria. In summary, this study demonstrates that Hg exposure is associated with increased odds of having lower GFR in the US population aged 40 or above. A statistical association with albuminuria was not apparent. We also observed that omega-3 FA intake may play a preventive role in Hg-induced nephrotoxicity. Additional studies are warranted to determine the sources, exposure routes, and forms of Hg most responsible for observed associations.