Risk assessment for migration of styrene oligomers into food from polystyrene food containers.

Regulation EU 10/2011 requires a risk assessment of Non Intentionally Added Substances (NIAS) migrating into food for food contact plastics within the EU. Styrene oligomers are important potential components of NIAS in polystyrene used for food packaging and so far only dimers and trimers have been identified. They are not genotoxic in vitro, and there is good evidence that they are not endocrine disruptors. Hazard characterization to establish "safe" exposure levels is based on 1. The No Adverse Effect Level (NOAEL) of 1 mg/kg bw/d in an oral rat study during pregnancy and lactation and 2. The concept of Threshold of Toxicological Concern (TTC). Likely human exposure is derived from 1. the concentrations of dimers and trimers in food simulants or 2. in food and 3. the probabilistic FACET exposure estimation based on dimer and trimer concentrations in polystyrene and their potential for migration. The Margin of Safety as the relation of potential consumer exposure and the "safe" exposure level was always above 1 (apart from migration with 95% ethanol which is no longer recommended as an official food simulant for overall migration into fatty food) demonstrating that dimers and trimers in PS food packaging present a low risk for consumers.

Oligomers of styrene are not endocrine disruptors.

Oligomers of styrene have been identified in polystyrene (PS) polymer samples intended for food packaging. Such oligomers contribute to nonintentionally added substances (NIAS) that may migrate into food or food simulants and therefore have to be assessed for the potential risk to health. No oligomers larger than dimers and trimers of styrene have been found to be present in PS. Some in vivo and in vitro information indicative of an endocrine activity for some specific oligomers suggest concerns for their potential for endocrine disruption in humans. Data on endocrine activity available from in vitro and in vivo screening approaches and from non-guideline studies in experimental animals were evaluated. The different test methods were classified according to the OECD Conceptual Framework for Testing and Assessment of Endocrine Disruptors (OECD) and the ranking system of Borgert et al. proposed in 2014. The quality and reliability of each study is further assessed by professional judgment. The integration of the total information supports the conclusion that neither specific oligomers, nor their mixtures, potentially migrating into food are endocrine disruptors according to the definition of EFSA and WHO/IPCS.