Seasonal Variation and Health Risk Assessment of Aflatoxin M1 in Milk From the Central Region of Iran

Aflatoxin M1 (AFM1) contamination in milk is a major public health concern due to its carcinogenicity and resistance to processing.

This study assessed seasonal variation in AFM1 levels across raw, pasteurized and ultra-high-temperature (UHT) milk and quantified associated non-carcinogenic and carcinogenic risks.

A total of 180 samples were collected over four seasons (October 2024-2025), and AFM1 concentrations were measured using HPLC-fluorescence detector (FLD). Distributional characteristics were described using medians and 95th percentile (P95) values, and prevalence estimates were reported with 95% confidence intervals. A health risk assessment was conducted using the estimated daily intake (EDI), hazard index (HI) and margin of exposure (MOE).

AFM1 was detected in all samples (6.10-176.20 ng/kg). Overall, 23.33% (95% CI: 17.7%-30.1%) exceeded the Iranian limit (100 ng/kg), and 58.88% (95% CI: 51.6%-65.8%) surpassed the EU limit (50 ng/kg). Seasonal analysis showed substantially higher contamination during warm months, with raw milk in summer presenting the highest upper tail concentration (P95: 168.57 ng/kg). Risk assessment based on P95 exposure indicated medium non-carcinogenic risk (HI: 1-10) for children across all milk types and for adults consuming raw milk. Carcinogenic risk characterization showed MOE values below 10000 for children consuming raw and pasteurized milk, indicating inadequate safety margins. These findings demonstrate that reliance on mean AFM1 concentrations underestimates health risks, especially for children. The pronounced seasonal patterns highlight the need for strengthened monitoring and targeted control strategies, with priority given to raw milk during warm seasons to protect vulnerable paediatric populations in Iran.