Determination of aflatoxin M 1 in urine samples indicates frequent dietary exposure to aflatoxin B 1 in the Bangladeshi population.

Aflatoxin B ₁ (AFB ₁ ), a hepatocarcinogen and highly toxic mycotoxin, is a contaminant of food commodities, especially in hot and humid climates that favour the growth of aflatoxin-producing fungi. As data on AFB ₁ contamination of food and feed in Bangladesh are scarce, we conducted an initial screening by ELISA on the occurrence of the metabolite and biomarker aflatoxin M ₁ (AFM ₁ ) in urines from Bangladesh which indicated frequent exposure. This finding led us to conduct a follow-up study where we applied a more sensitive method (IAC clean-up and HPLC-FD analysis) to determine AFM ₁ concentrations in a larger set of urine samples. To account for possible seasonal and regional differences in mycotoxin exposure, in total 218 urines were collected in two districts of Bangladesh: 164 urines (n=69 in summer, n=95 in winter) from residents of a rural and an urban area in Rajshahi district, among them 62 participants enrolled in both sampling periods, and 54 urine samples obtained from pregnant women in Dhaka district. AFM ₁ was detected in>40% of all Rajshahi urine samples at a range of 1.7-104pg/mL in summer and at a range of 1.8-190pg/mL in winter season. The mean level of urinary AFM ₁ was higher in winter (27.7±42.6pg/mL) than in summer (13.6±21.2pg/mL) season, and differences were observed at the mean AFM ₁ level between the rural and the urban Rajshahi cohort. AFM ₁ was found less frequently in the Dhaka pregnant women (31% above LOD, mean 13.9±33.3pg/mL), but in a similar concentration range (1.7-141pg/mL) as in the Rajshahi cohort. Urinary AFM ₁ levels did not show significant associations with the participants food consumption pattern. In conclusion, when compared to biomarker data from other countries, detection frequency and urinary AFM ₁ levels in our Bangladeshi cohorts raise concerns regarding their exposure to potent carcinogenic aflatoxins.
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