Health risk assessments of heavy metals and trace elements exposure in the breast milk of lactating mothers in the Northeastern Iran

Mother's breast milk is a natural and complete food for infants but can be a main source of exposure to toxic pollutants. These pollutants can negatively affect the health of the infant. Therefore, conducting biomonitoring surveys is essential to evaluate such health effects in toxicological research. This study aimed to estimate the probable health risks for infants exposed to essential and non-essential trace elements through breast milk ingestion. This descriptive-analytical, cross-sectional study was performed on 90 breastfeeding mothers referred to the health centers in Mashhad, Iran in January 2021. The health risk assessments (carcinogenic and non-carcinogenic risk) were estimated using chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI), and lifetime carcinogenic risk (CR), which were recommended by the US Environmental Protection Agency (US EPA). The results of the HQ values of trace elements through ingestion exposure for arsenic (90%), copper (90%), zinc (40%), and iron (10%) exceeded the threshold of HQ, and arsenic (66.59%), copper (16.91%), and zinc (9.68%) and iron (4.57%) had the highest contribution to increasing the HI index. The average value of CR was 5. 08 x 10(-3). Chromium and iron showed significant relationships (P<0.05) with education level and disease background in this study, and the concentration of chromium, iron, and zinc in the breast milk samples significantly changed during lactation stages (P<0.05). Overall, the risk of carcinogenicity through exposure to breast milk for infants was higher than the safety level of US EPA risk. Therefore, there could be a potential health risk of trace elements, particularly arsenic, copper, and zinc for infants in Mashhad, Iran through the consumption of mothers' breast milk. More efforts are required to control and reduce routes of receiving trace elements in breastfeeding mothers by the competent authorities.