Dietary Risk Assessment of Cyromazine and Its Analogue Melamine in Evaporated and Infant Milk Samples in Nigeria

The safety of milk is considered as a significant public health consideration and has been a key concern for consumers worldwide. The concentrations of cyromazine and its metabolic product, melamine, and their dietary risk assessment are investigated in this study.

A total of 182 milk samples containing 15 brands were sampled between June and December 2022 from major and retail markets in Nigeria. After a solid-phase extraction procedure, the concentrations of the two compounds were determined using High-Performance Liquid Chromatography coupled with a Diode-Array Detector. Solid-phase extraction was utilized to extract local and imported evaporated and infant milk with CCl3COOH and CH3CN, followed by clean-up with NH4OH in MeOH. The extracts were analyzed with Agilent High-Performance Liquid Chromatography, including a Zorbax Eclipse+C18 column.

For both melamine and cyromazine, the Limits of Detection and Limits of Quantification were 1.29-1.48 and 3.94-4.50 µg/kg, respectively. The precision (Relative Standard Deviation<1), recovery (99.5–102.5%), and regression (r2=0.989) were all excellent. Melamine concentration ranged between 57.6±18.9 and 930.3±379.9 µg/kg among the samples, and cyromazine was 57.2±12.3 and 670.9±87.8 µg/kg. Brand 2, imported from Holland, had the highest detection frequency for the two analytes. Disturbing levels of melamine were detected in Brand 2, particularly that 75 and 95% of the samples had melamine above the acceptable Maximum Residue Limit.  However, the estimated daily exposure to the two additives was below the allowed daily intake values, and the Hazard Index (HI) in the different milk samples ranged from 0.02 to 1.22, with one sample having HI>1.

The exposure risk of melamine and cyromazine among the general population is acceptable, and smaller HI values demonstrated no significant potential risk for the Nigerian population according to the recommended guidelines. Regulatory agencies are encouraged to step up their surveillance activities to forestall the inclusion of prohibited additives in local and imported milk to protect public health.