Identification of non-intentionally added substances migrating from inner coatings of metallic cans – Toward provisional risk assessment of oligoesters
Résumé
Since the decline in the use of bisphenol A, the chemistry of varnishes and coatings applied to the inner surfaces of metallic food contact materials (FCMs) is poorly documented. We hypothesised that can coatings are now diversified and bring forth various non-intentionally added substances (NIAS) to be described. The study of complex components such as NIAS requires demanding non-targeted approaches. In a preliminary study[1], the coatings of 12 vegetable cans from the French market, where BPA is banned from all FCMs since 2015, have been investigated. Using LC-HRMS, more than 125 substances were pinpointed, among them additives such as epoxidised soybean oil and various NIAS. Mostly, 84 oligoester combinations from 8 diols and 4 diacids represented the dominant family. The stepwise organic synthesis of native and deuterated combinations of neopentyl glycol and isophthalic acid enabled a higher confidence level and monitoring in vegetable extracts. Migration of oligoesters averaged 330 µg/kg in the drained vegetables (43 to 1600 µg/kg). This preliminary study highlighted the need to carry out a proper risk assessment of this NIAS family (risk characterisation). Further, a collaborative research project (acronym OLIGO) funded by the French National Research Agency is on-going to inform a provisional risk assessment related to oligoesters migrating from polyester-based food can coatings. One year after the project was launched, a representative set of 7 individual reference standards has been synthesised, laying the foundation for exposure and toxicological investigations. In particular, on-going work involves (i) exposure assessment by sampling ~300 canned food products with planned identification of oligoesters and semi-quantification in foodstuffs, and (ii) in vitro assessment of individual substances, focusing on genotoxicity, endocrine disrupting mode of action, human liver metabolism (using tritium-labelled compounds) and gastrointestinal fate.
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