Mercury exposure in breastfeeding mothers and associated health risks to infants: Evidence from breast milk and nail biomarkers.

Mercury (Hg) is a toxic environmental pollutant that can enter the human body through diet and environmental exposure and may be transferred to infants via breastfeeding. This study aimed to determine Hg concentrations in maternal fingernails and breast milk, identify factors influencing mercury levels in milk and assess potential health risks to breastfed infants. A total of 74 breastfeeding mothers were engaged from urban health centers. Hg concentrations were measured using atomic absorption spectrophotometry and dietary, maternal and infant characteristics were recorded through structured questionnaires. Hg concentrations in maternal fingernails ranged from 0.30 to 9.71 μg/g. In contrast, Hg levels in breast milk showed a narrower range 0.60-1.90 μg/L. Breast milk Hg levels did not differ significantly by maternal occupation, tablet use or fish consumption patterns (p > 0.05). Correlation analysis revealed a positive association between breast milk Hg and length of pregnancy (r = 0.323, p = 0.002) and a negative association with infant body weight (r = -0.327, p = 0.002). Multiple linear regression identified maternal age, infant age, fruit consumption, baby weight, number of children and dental filling history as significant predictors of mercury levels in breast milk (p < 0.05). Health risk assessment showed that the estimated daily intake of mercury exceeded the reference dose (0.16 μg/kg/day), with target hazard quotient values greater than one across all subgroups indicating a potential non-carcinogenic risk to breastfed infants. These findings highlight the need for continued monitoring of maternal mercury exposure while supporting safe breastfeeding practices.