New test methods for plastic and rubber product safety
JRC scientists have developed new methods to measure the content and migration of Polycyclic Aromatic Hydrocarbons (PAHs) from rubber and plastic items.
PAHs are a group of hazardous compounds - many of which are known carcinogens - that can be found in the raw materials used in the manufacturing process of products ranging from children's toys to bicycle grips and sporting goods. They are also found in products made from secondary raw materials, such as granules and mulches used in synthetic turf pitches, or in loose forms at playgrounds and other sports facilities.
Considerable public attention has been paid in recent years to the potential for children and adults to be exposed to PAHs through skin contact, including inside the mouth. While current EU legislation already limits PAH levels in consumer products, these new methods give laboratories a novel, sensitive and cost-effective analytical method to determine PAH content in rubber and plastic. They will also enable tests to be carried out to reliably determine the migration rate of PAHs from these products, should a migration based limit for PAHs be considered in the future.
This scientific advancement equips the European Commission with the latest information as it considers possible updates to the legislation. The developed PAH content method will be of use in determining compliance of plastic and rubber consumer articles with the current restriction on PAHs and feeds into current work initiated by the European Committee for Standardisation (CEN), at the request of the Commission, to develop a harmonised standard. It will also be of benefit to owners and operators of sports fields to determine compliance with limits that could be proposed in the context of the on-going restriction process.
Information on the migration behaviour of PAHs and a method to measure migration is important to support the underlying risk assessment of PAHs in rubber and plastics products and offer the possibility of considering the introduction of limits based not only on content, but also on migration.
What's currently in place to protect people?
The EU's Regulation for the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) restricts the content of eight PAHs in the plastic and rubber parts of articles supplied to the general public. These eight are known to have potentially cancer-causing properties.
Sources of PAHs include raw materials, frequently used in the manufacturing process of rubber and plastic articles, such as extender oils and carbon black. The restriction of PAH in consumer articles tackles the risk that people could receive a dose of PAHs migrating from these rubber and plastic components and entering the body through the skin.
At the time the regulation was adopted, there were no reliable testing methods to determine the levels at which PAHs in these articles may enter the body through contact with the skin. As a result, the REACH restriction was defined in terms of the bulk content of PAH, rather than in terms of the amounts that migrate from the article.
The relevance of the availability of sensitive analytical methods, as well as of migration was acknowledged at the time, as the regulation states that "the limit values shall be reviewed in the light of new scientific evidence". The JRC has worked to provide this new evidence by studying the migration behaviour of PAHs from plastic and rubber samples, using models that simulate skin contact as realistically as possible. The new test methods do not use animals.
How did scientists improve test methods?
Scientists used a set of manufactured polymeric rubber and plastic samples as well as rubber granules (coated and uncoated) from 'end of life' tyres - the type that are often recycled to provide the filling for artificial sports pitches.
These samples were used to test the ability of certain simulants to accurately reflect the release potential of PAHs from plastics and rubber. These were:
- artificial water-based sweat and saliva simulants;
- fat-based formulations such as skin surface film liquid (SSFL), which aim to realistically simulate the composition of the skin;
- 20% aqueous ethanol which, according to scientific literature, has been proven to correlate well with human skin absorption.
As well as being validated in-house, the suitability of 20% aqueous ethanol was assessed in an inter-laboratory comparison study with 21 laboratories from seven EU Member States.
Taking into account the simplicity to prepare the migration medium as well as the good correlation with skin studies, scientists concluded that aqueous ethanol is the best option for standardised migration tests in laboratories across Europe. The methods are now suitable for use in future product-to-skin migration studies.