Mercury, Lead, Cadmium, and Barium Levels in Human Breast Milk and Factors Affecting Their Concentrations in Hamadan, Iran.

Breast milk is considered the best source of nutrition for all infants. However, exposure of newborns to toxic metals is of special interest due to their potential harmful effects. Thus, the primary aims of this study were to determine the concentration of toxic heavy metals including lead, mercury, cadmium, and barium in breast milk samples from Hamadan, Iran, in relation to some sociodemographic variables. A total of 100 breast milk samples were collected and their heavy metal contents were measured by inductively coupled plasma mass spectroscopy (ICP-MS). The median breast milk concentrations of Pb, Hg, and Ba were 41.9, 2.8, and 1.95 μg/L, respectively. Cd levels were < 1 μg/L in all samples. The Pb level in 94% of the samples was higher than the recommended Pb limit of < 5 μg/L in breast milk suggested by World Health Organization (WHO). Hg levels in 54% of the breast milk samples were higher than the normal mean concentration (1.7 μg/L) suggested by WHO. We found no correlation between Hg levels in breast milk and sociodemographic factors. Ba levels in all the breast milk samples were lower than the WHO's proposed health-based drinking water guideline (0.7 mg/L). Considering the results of the present study and the vulnerability of infants, along with the well-known toxicity of these metals, further studies are warranted to identify the main sources of exposure that contribute their concentration in breast milk, establish harmless intake values of toxic metals in breast milk, and develop preventive measures.