Melamine and its derivatives in Australian pooled urine samples from 2012-2013 and 2022-2023

Melamine is a versatile compound with various industrial and commercial applications, and the long-term use has resulted in its widespread occurrence in the environment. Furthermore, illicit addition of melamine into food products has raised interest in this compound. The aim of this study was to provide the first assessment of exposure to melamine and its derivatives in the Australian population. De-identified urine specimens collected in 2012-2013 and 2022-2023 were obtained from a community-based pathology laboratory and were pooled based on sex and age groups (n = 48 pools of 100, to a total of 4800 individual samples). Melamine, cyanuric acid (CYA), and ammelide were frequently detected in the pooled urine samples, with mean concentrations of 4.3, 94, and 4.2 ng/mL, respectively. A U-shaped trend in urinary concentrations of melamine was identified as age increased. Children and adolescents (< 15 years old) represented key groups for high exposure to CYA, whereas older individuals (≥45 years old) had higher exposure risk to ammelide. No temporal or sex differences was observed in urinary concentrations of melamine and its derivatives. Compared to other countries, high concentrations of CYA were observed in samples collected from the Australian population. From the estimated CYA daily intakes, 21 % of urine pools exceeded reference doses (2.5 μg/kg bw/day). To the best of our knowledge, this is the first study to reveal continued exposure of melamine and its derivatives in the Australian population and underscore the age trends of their urinary concentrations.