A review of metal(loid) contamination in breast milk: from environmental exposure to infants’ perils

Metals and metalloids are now present in all environmental compartments and come into contact with humans through various pathways. Breast milk transmission is one route through which infants may get affected. In this paper, we review studies on the occurrence of metal(loid)s such as arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), and mercury (Hg), which are of significant concern to human health in breast milk and assess their potential risks to breastfeeding mothers and infants. Breast milk is a complete source of nutrition for infants. Along with essential vitamins, minerals, and immunological factors required for growth and development infants may also be exposed to metal(loid)s transferred through maternal milk via different pathways like water, air, and food. Infant’s rapid growth and immature organs increase their vulnerability to these toxicants. Metal(loid) concentrations in breast milk depend on maternal diet, health status, and environmental exposure. Despite the primacy of breastfeeding, it can also serve as a source of metal(loid) exposure. Reports indicate that the tolerable daily intake of As is exceeded in 75% of breast milk samples in Asia, with concentrations ranging from 0.1 to 100 μg/L. Moreover, 73% of breastmilk samples reported elevated levels of Cd (0.72±0.42), exceeding the TDIWHO for Cd. Another important finding is that in 40% breastmilk samples, the levels of Cd, Cr, As, and Pb were all above the World Health Organization limits. 8.4% of breast milk samples exceeding the RV95 (reference value for 95th percentile) Cd reference limit (2.5 μg/L) indicates the increased maternal exposure to contamination. Moreover, total Hg exceeded screening RV95 (3.5 μg/L) in approximately 8% of breast milk samples, particularly among high-fish-eating individuals. Therefore, based on the above findings, it is essential to quantify metal(loid) concentrations in breast milk and implement appropriate measures to minimize exposure. Although the benefits of breastfeeding outweigh the potential risks posed by these metals and metalloids to infants, continuous monitoring of these contaminants remains crucial, along with the implementation of strategies to reduce associated risks. Therefore, the issue of metal(loid)s in breast milk needs extensive research, proper investigation, and regular status updates.