A pilot study on nitrate and nitrite concentration in breast milk: probabilistic risk assessment in breastfed infants

Breast milk is the primary source of nutrition for infants, providing essential nutrients and supporting immune development during early life. However, in addition to beneficial components, breast milk may contain environmental contaminants, which may pose potential health risks to the infants based on exposure levels. This study evaluated nitrate and nitrite exposure and associated health risks in exclusively breastfed infants during the first 6 months of life. Breast milk samples were collected from 93 lactating mothers with infants aged 0-6 months in Hamadan, Iran. Infants were categorized into three age groups 0-2, 2-4, and 4-6 months. Infant age, body weight, and daily milk consumption were obtained by interviewing with the lactating mothers. Nitrate and nitrite concentrations were determined using ion chromatography. Estimated daily intake was calculated, and health risk was characterized using Monte Carlo simulation to evaluate non-carcinogenic and carcinogenic risks. Nitrate and nitrite were detected in all breast milk samples but estimated exposure levels for infants remained lower than the acceptable thresholds across all age groups. Maternal body mass index, age, and educational level showed no significant association with nitrate or nitrite concentrations in breast milk. Considering their role as precursors of nitric oxide, the detected concentrations may contribute to physiological processes without posing measurable health risks. These findings support the safety of breastfeeding with respect to nitrate and nitrite exposure in 93 breastfeeding infants in Hamadan city and provide new evidence on early-life exposure assessment. Further biomonitoring studies by considering vast geography and more sample size are recommended to better characterize exposure pathways and long-term health implications.