Aflatoxin M₁ Levels in Milk and Urine Samples of Nursing Mothers in Bangladesh: Exposure Assessment of Infants

Abstract

Breast milk is the ideal source of nutrition for infant growth and development. However, when nursing mothers consume aflatoxin B1 (AFB1)-contaminated food, the hydroxylated form aflatoxin M1 (AFM1) is transferred to breast milk and urine. AFB1 and its metabolite AFM1 are potent carcinogens and can pose significant risks to food safety and public health worldwide. This study determined the prevalence of AFM1 in the breast milk and urine of nursing mothers in Bangladesh and estimated infant exposure to this toxin. Breast milk and urine samples (72 each), collected from nursing mothers in three different regions of the country, were analyzed for AFM1 occurrence via a sensitive enzyme-linked immunosorbent assay (ELISA). AFM1 was present in 88.9% of urine samples, with a mean concentration of 109.9 ± 52.8 pg/mL, ranging from 40.0 to 223.8 pg/mL. AFM1 was also detected in 50% of the breast milk samples, with a mean concentration of 4.6 ± 0.7 pg/mL, ranging from 4.0 to 6.1 pg/mL. A strong correlation (r = 0.72) was observed between milk and urinary AFM1 levels, indicating these as suitable biomarkers of AFB1 exposure. Yet, no significant correlations were identified between AFM1 levels in either milk or urine and the food items typically consumed by nursing mothers. The average estimated daily intake (EDI) for AFM1 with breast milk was 0.59 ng/kg bw/day, with no significant difference between infants (0.57 ng/kg bw/day) and toddlers (0.65 ng/kg bw/day). A comparison of computed EDI ranges for AFM1 with a proposed tolerable daily intake value resulted in Hazard Indices below 1 for all exposure scenarios. This indicates that the AFM1 concentrations in breast milk from three regions of Bangladesh raise no concern. Also, the measured levels were far lower than the maximal levels set in the EU regulations for AFM1 in dairy milk and infant formula (50 ng/kg and 25 ng/kg, respectively).

Keywords

• aflatoxin M₁
• Bangladesh
• biomarker
• breast milk
• urine
• contaminant