Occurrence of Melamine and Cyanuric Acid in Breast Milk: A Risk Assessment for Infants Aged 0–6 Months

Melamine (MEL) and cyanuric acid (CYA) are contaminants that can enter the human body through dietary sources, raising significant toxicological concerns, particularly for infants. MEL undergoes minimal biotransformation in the human body. While breast milk is widely recognized as the optimal source of nutrition for infants, it may also serve as a potential route for the transmission of contaminants. This study aimed to quantify the concentrations of MEL and CYA in breast milk and assess the associated non-carcinogenic toxicity risks for infants aged 0–6 months. A total of 100 mothers from Hamadan, Iran, who exclusively breastfed their infants aged 15–150 days, were included. Breast milk samples, ranging from 10 to 50 mL, were manually expressed. The results revealed that 77% of the samples contained MEL, while 84% contained CYA, both exceeding the detection limits. The average concentrations of MEL and CYA were 730 ± 26 and 400 ± 38 ng mL⁻¹, respectively. Risk assessment indicated that none of the infant groups exhibited a hazard quotient (HQ) or cumulative risk (hazard index) from MEL and CYA exposure. According to Monte Carlo simulation, the 95th percentile of HQ for MEL and CYA in breast milk were 0.00561 and 0.0000154, respectively, both well below the safety threshold (HQ < 1). These findings suggest that breast milk consumption by infants up to 6 months of age in Hamadan does not pose a significant risk in terms of MEL and CYA exposure.