September 8, 2017 by Rhiannon Smith

As part of our work with the European REACH Grease Thickeners Consortium (ERGTC), wca are currently preparing sector specific guidance documents to assist companies with their REACH registrations and risk assessments for grease thickeners, and potentially other substances, manufactured in situ in base oil. This work builds on the poster which wca presented at SETAC earlier this year (Brussels, May 2017) on behalf of the ERGTC: “Matrix effects, bioavailability and the risk assessment of grease thickeners in situ in base oil”.

Currently, the European Chemical Agency (ECHA) have links to sector specific guidance on their website for groups of chemicals (metals, fragrances, etc.). During a face to face meeting between ECHA and the ERGTC in September 2016, the ERGTC proposed that they also prepare sector specific guidance on the handling of substances which are manufactured in situ in base oil. The ERGTC are currently looking to inform relevant stakeholders of their intention to produce sector specific guidance, its purpose and what type of information it will include. To this end, they have contacted other potentially relevant stakeholders and are also publishing their intention through more widely available literature, such as the Eurogrease magazine.

The purpose of the guidance will be to ensure that a consistent approach to REACH registration of grease thickeners is taken across the sector. Grease thickeners are primarily, but not exclusively, metal salts of carboxylic acids (mono or di-carboxylates), or polyureas, which form a matrix within an oil base, and are generally manufactured in situ in base oil.

The sector specific guidance will outline an ERGTC specific registration strategy which advocates testing of the isolated substance, where possible, but which also takes into consideration the chemical properties of grease thickeners and their use within a grease matrix. The approach is intended to avoid unnecessary animal testing through the development of a pragmatic, intelligent and exposure-based testing strategy.

The sector specific guidance will include the following topics which are applicable for grease thickeners but which may also have much in common with registration of other types of substance manufactured in situ in a grease base:

  • The nature of grease thickeners and how they are almost exclusively manufactured and used within a grease base;
  • Justification for why grease thickeners are registered as isolated substances;
    • Practical considerations for registrants
    • Scientific justification based on chemical characterisation and electron micrographs
  • Information on chemical analysis and substance identity;
  • Technical challenges for hazard testing; and
  • Bioavailability testing which takes into consideration the fact that most ERGTC substances are only ever manufactured and used within a grease matrix, so exposure to grease thickeners will be minimal because of their limited bioavailability.

The bioavailability testing approach is based on a theory outlined in the OECD Emission scenario document on lubricants and lubricant additives that, in environmental media, the majority of additives (or, in the present case, grease thickeners) will remain within the oil base (or, in the present case, oil/grease matrix) due to their partitioning properties. There will therefore be limited (or ‘not significant’ using terminology from ECHA guidance R5) environmental or human health exposure because the substance(s) are expected to have limited bioavailability. The ERGTC are conducting experimental testing to develop this hypothesis and to include as information to support the REACH registration strategy.

There are different types of grease thickener and not all the substances have properties that mean that they will not leach from the grease base. A flow chart is therefore being developed, to show how the results from bioavailability testing can be used as part of a REACH registration strategy. This flowchart, shown in Figure 1, is not definitive and is being refined based on the results from ongoing experimental work.

Figure 1: Proposed flow chart for testing of grease thickeners