Oligoesters migrating from food can coatings – Filling risk assessment gaps – Oligo

Within the project OLIGO, the main scientific bottleneck – the unavailability of representative authentic standards – will be tackled through the organic synthesis of native compounds as well as deuterium- and radio-labelled compounds, in order to (i) comprehensively identify the oligoesters present in marketed cans, (ii) quantify their migration into food and (iii) assess in vitro their metabolism and potential toxicity to human. Exposure assessment of the French population will be balanced with hazard identification aspects in order to establish a provisional risk assessment and further recommendations.
Addressing the challenge of characterising NIAS such as oligoesters requires resources and information which are not available to most of the agro-industrial stakeholders. Five public and academic partners are involved in OLIGO. CEISAM (CNRS UMR 6230, Nantes) will provide other partners with a set of representative authentic standards to be synthesised stepwise. LABERCA (INRAE UMR 1329, Nantes) will coordinate the project and will achieve oligoesters’ identification in coatings and their quantification in foodstuffs. To this end, a previously developed workflow will be applied to identify oligoesters, with much attention paid to the sample preparation of foodstuffs. LNC (INSERM UMR 1231, Dijon) will study genotoxicity, performing in vitro regulatory bioassays based on OECD guidelines, and endocrine disruption potencies, performing bioassays of the level 2 (mode of action) of OCDE framework. TOXALIM (INRAE UMR 1331, Toulouse) will carry out in vitro human liver biotransformation assays (hazard identification, biomarker metabolites) and gain a broader understanding of the fate of oligoesters. ANSES, the French agency for food, environmental and occupational health & safety, will define a sound sampling plan and lead the output provisional risk assessment.

The project has been launched in October 2021.
Three months after the start, the first deliverable concerning the list of 7 compounds to be synthesized was finalised. The selected compounds are cyclic combinations of neopentyl glycol, 1,4-butanediol, hexanediol, tricyclodecanedimethanol, isophthalic acid and adipic acid.
The synthesis, scheduled for 1 year, began using an already proven a stepwise strategy. Three types of compounds are planned: (i) natives for identification and quantification in food as well as for in vitro toxicological assays, (ii) deuterium-labelled for quantification in food, and (iii) 14C-labelled for investigating the hepatic biotransformation products.

A side project is currently being prepared for the investigation of the gastrointestinal fate of the synthesis oligoesters.

The preliminary study (used for setting up the OLIGO project) was submitted to an international peer-reviewed scientific journal in December 2021. It presents the stepwise organic synthesis strategy, an exhaustive database of theoretical combinations of oligoesters and an application to the identification of compounds which migrate from the inner coatings and varnishes of vegetable cans sampled in a supermarket, i.e. without prior knowledge of the formulations.

The OLIGO project aims at stimulating and supporting a thorough risk assessment related to the dietary exposure of the French population to cyclic oligoesters migrating from polyester-based coatings into canned foodstuffs. It addresses a timely and important public health issue related to the chemical safety of food that has not yet been resolved
Epoxy-resins based on bisphenol A (BPA) diglycidyl ether have traditionally been used worldwide in internal coatings applied to metallic food contact materials. Due to concerns of both consumers and the scientific community, restrictions have been applied at the EU scale on the use of BPA, including a ban in baby bottles and a drastic specific migration limit from plastics or varnishes and coatings to food. In France, a complete ban of BPA entered into force in 2015. Industrial stakeholders have conceded enormous efforts to adapt through the evolution of technologies and conservation processes.
Polyester-based coatings have grown into predominant alternatives to BPA-based epoxy resins. A large range of polyol- and polyacid-monomers, for which migration into foodstuffs is under control, may be used, offering numerous polyester combinations.
However, oligoesters, which are non-intentionally added substances (NIAS) constitutive of polyester-based coatings arising from incomplete polymerisation reactions (up to 2% of the resin's weight, mostly cyclic combinations of 4 to 8 monomers), have not yet been subjected to a robust and transparent risk assessment, their wide chemical diversity raising analytical issues. So far, missing data relate to (i) our knowledge on the extent of polyester-based coatings' use on the market (France standing apart), (ii) the comprehensive identification of oligoesters, (iii) the related human exposure following migration into food, and (iv) their fate (e.g. liver biotransformation and potential bioactivation triggering adverse effects).
Within the project OLIGO, the main scientific bottleneck – the unavailability of representative authentic standards – will be tackled through the organic synthesis of native compounds as well as deuterium- and radio-labelled compounds, in order to (i) comprehensively identify the oligoesters present in marketed cans, (ii) quantify their migration into food and (iii) assess in vitro their metabolism and potential toxicity to human. Exposure assessment of the French population will be balanced with hazard identification aspects in order to establish a provisional risk assessment and further recommendations.
Addressing the challenge of characterising NIAS such as oligoesters requires resources and information which are not available to most of the agro-industrial stakeholders. Five public and academic partners are involved in OLIGO. CEISAM (CNRS UMR 6230, Nantes) will provide other partners with a set of representative authentic standards to be synthesised stepwise. LABERCA (INRAE UMR 1329, Nantes) will coordinate the project and will achieve oligoesters’ identification in coatings and their quantification in foodstuffs. To this end, a previously developed workflow will be applied to identify oligoesters, with much attention paid to the sample preparation of foodstuffs. LNC (INSERM UMR 1231, Dijon) will study genotoxicity, performing in vitro regulatory bioassays based on OECD guidelines, and endocrine disruption potencies, performing bioassays of the level 2 (mode of action) of OCDE framework. TOXALIM (INRAE UMR 1331, Toulouse) will carry out in vitro human liver biotransformation assays (hazard identification, biomarker metabolites) and gain a broader understanding of the fate of oligoesters. ANSES, the French agency for food, environmental and occupational health & safety, will define a sound sampling plan and lead the output provisional risk assessment.