Migration of Polycyclic Aromatic Hydrocarbons (PAHs) from plastic and rubber articles

Polycyclic Aromatic Hydrocarbons (PAHs) constitute a large group of chemically related substances many of which are known carcinogens. To minimise human exposure there are already several pieces of EU legislation which limit their presence in certain food products, as well as in water and ambient air. Under the REACH regulation (EC 1907/2006 Annex XVII, Entry 50), eight priority PAHs have for some time been restricted in extender oils used in tyres. Although not added deliberately to consumer products, PAHs can still be present as impurities. An amendment of the above mentioned legislation (Regulation EU 1272/2013) establishes content limits for the eight PAHs of 0.5 mg kg-1 for plastic and rubber components of toys/childcare articles, and 1 mg kg-1 for all other consumer articles, in direct and prolonged, or short-term repetitive, contact with the skin or oral cavity. In May 2016 DG JRC and DG GROW signed an Administrative Arrangement (AA 34003) known as the STANPAHs project. The main objective of this contract was for the JRC to provide scientific support in the implementation and potential amendment of the restriction on polycyclic aromatic hydrocarbons, in particular concerning paragraphs 5 and 6 of entry 50 of Annex XVII to the REACH legislation. The main objectives of the project were: a) to gain a better understanding of the migration behaviour of certain PAHs in plastic and rubber components of articles, and b) to develop a reliable methodology to determine PAH migration from these matrices, under conditions simulating, to the best possible extent, dermal contact (including the oral cavity). This report presents the outcomes of the experimental studies carried out at JRC and the achievements towards fulfilling these objectives. A set of manufactured polymeric plastic and rubber matrices, to be used as test materials in the project, has been chosen based on criteria such as their frequency of use in articles within the scope of the restriction and the likelihood of the presence of high PAH contents (e.g. due to their content in carbon black or extender oils). Various grades and types of ingredients known to be PAH sources were used in the formulation of the manufactured ad-hoc materials. The test materials included low density polyethylene (LDPE), polystyrene (PS) and polyvinyl chloride (PVC) as plastic matrices, and ethylene-propylene diene monomer (EPDM), natural rubber-butadiene rubber (NR-BR) and silicone as rubber matrices. Moreover, recycled granules (coated and uncoated) originating from end-of-life tyres produced before and after 2010 as well as rubber tiles made of the recycled coated granules were also made available for this study. The content of each of the eight restricted PAHs was measured by using a method developed in-house based on Randall hot extraction, purification by Solid Phase Extraction based on Molecular Imprinted Polymers, and Gas Chromatography Mass Spectrometry determination. A number of experimental studies were undertaken to generate data and information to improve the knowledge on migration of the target PAHs. Migration parameters operated in the STANPAHs project to estimate migration rates were as follows: dynamic mode at 40°C for 24 hours using a variety of migration media including artificial aqueous simulants, modified biosimulants formulations with lipidic content such as skin surface film liquid (SSFL), and 20% ethanol in water. According to scientific literature the use of 20% ethanol as the migration medium proved to correlate well with human skin absorption. Using these conditions, migration of the target PAHs into artificial sweat (EN1811) and artificial saliva (DIN53160-1) was not detected in any of the materials studied. Moreover none of the plastic polymeric materials led to detectable release of the target PAHs in any of the migration media used in this study (i.e. artificial sweat and saliva, skin surface film liquid (SSFL), and 20% ethanol solution). Similarly the tests with silicone materials did not result in detectable migration. Only the rubber matrices containing Distillate Aromatic Extract (DAE) as extender oil showed detectable migration when using 20% ethanol as the migration solution. In addition, the release of PAHs from coated recycled rubber granules was lower than from the uncoated granules suggesting that the coating acts as a barrier to chemical migration. According to industrial partners DAE is not used by European industries for manufacturing of parts of articles intended for skin contact. The materials containing DAE, although not representative for marketed products, have been made available to facilitate migration testing method development. The migration test method using 20% ethanol has been validated in-house and shows good method performance allowing the determination of PAH at trace level. Furthermore it has been considered for an initial inter-laboratory comparison study (ILC) aiming to investigate method applicability and transferability in a variety of laboratories. The within-laboratory precision, expressed as the relative standard deviation for repeatability (RSDr), and the between-laboratory precision, expressed as the relative standard deviation for reproducibility (RSDR) were assessed. In general the RSDR ranged from 28 to 113% and the RSDr from 7 to 23%. It is worth remembering that the level of PAH migration was very close to the quantification limit of the method and therefore this variability can be expected. Similar values have been reported in a recent German study with the participation of 9 laboratories on the migration of PAHs from rubber materials in contact with aqueous ethanol. The fact that better values of RSDr and RSDR were obtained for chrysene and benzo(e)pyrene that had the highest concentrations in the final migration solutions and that the analysis of the control solution used in this exercise showed a good reproducibility (RSDR%