A nationwide survey of the occurrence of melamine and its derivatives in archived sewage sludge from the United States

Highlights: • Melamine and its derivatives were consistently detected in sludge samples. • ∑Melamine concentrations in sludge ranged 34–1800 ng/g dry weight. • Melamine was prevalent in sludge, followed by cyanuric acid. • Emission of ∑melamine through U.S. biosolids was estimated at 1600 kg/yr. -- Abstract: Melamine-based resins are used extensively in laminates, plastics, coatings, glues, and dinnerware. Little is known, however, about the occurrence of melamine and its derivatives in the environment. In this study, a nationwide survey of melamine and its derivatives, namely ammeline, ammelide, and cyanuric acid, was conducted, using archived sewage sludge samples collected from 68 wastewater treatment plants in the United States (U.S.). The sum concentrations of four target compounds in sludge ranged from 34 to 1800 ng/g dry weight (dw), with a mean concentration of 240 ng/g dw; melamine (46%) and cyanuric acid (40%) collectively accounted for 86% of the total mass of analytes. No significant geographical variation in the concentrations of melamine and its derivatives in sewage sludge was found. The estimated emission of melamine and its derivatives via land-application of sludge was approximately 1600 kg/yr in the U.S. The hazard quotient values for melamine in sludge-amended soils ranged from 2.2 × 10⁻⁵ to 4.4 × 10⁻³, indicating that the current levels of melamine in sludge pose a minimal risk to the soil environment.