ECHA

Communicating exposure scenarios and other information for mixtures further downstream is a complex task for industry. One approach formulators take is to develop safe use information based on the substances that present the greatest hazard and risk. "This is a good starting point," our guest contributors say. However, formulators are faced with various challenges. Our contributors tell us more.

Industry identified difficulties and complexities in handling exposure scenario information for substances in mixtures soon after the first REACH registration deadline and the first Practical Guide was published in 2010.

To communicate this information for substances in a mixture, the formulator typically needs to identify those substances that contribute most to the potential hazard and risk of the mixture. The DPD+*, among other approaches, provides a good starting point for developing safe use conditions.

Yet, more experience has now been gained and additional insights have come available on how to communicate information on safe use of mixtures. This issue has been explored in the Exchange Network for Exposure Scenarios (ENES) and identified as an action in the Chemical Safety Report/Exposure Scenario Roadmap.

As a joint activity, the European Chemical Industry Council (Cefic) and the Downstream Users of Chemicals Coordination Group (DUCC) are currently collecting approaches and methods used by companies and industry sectors. An initial evaluation of such methods is planned in the near future. These methods will also be presented at the fifth meeting of ENES from 21 to 22 November in Brussels. Several key issues have been identified through this work so far, and these are presented in this article. 

Options for communicating safe use information for mixtures

Several options for fulfilling the obligation to communicate information on the safe use of substances in mixtures have been identified and are outlined below. The preferred option depends on factors such as the role of the downstream user, the application and composition of the mixture, and the complexity of the supply chain.

Option A: Annexing relevant exposure scenarios of the substance components to the safety data sheet for the mixture.

This seems the most suitable option to communicate safe use info to downstream users who are formulators of mixtures, because this provides a good starting point to the downstream formulator for generating the safety data sheet for his (second level) mixture. It is not really a recommended option to communicate to end users of mixtures unless the appropriate risk management measures for the mixture are clearly specified.

Option B: Consolidating of safe use information derived from substances' exposure scenarios (top down approach).

In this case, safe use information for the mixture is derived from consolidating the exposure scenarios of the component substances received from suppliers. This is typically done on a case-by-case basis. Consolidating safe use information can be done in several ways. A key element of this approach is to identify the "lead" substances of the mixture for the various exposure pathways, e.g. via the DPD+ methodology*. This drives the selection of the relevant operational conditions and risk management measures to include in the safe use information for the mixture.

Option C: ‘Mixture use' based approach (bottom up approach).

The starting points for a ‘mixture use' based approach are the composition and typical uses of the mixture. This approach is mainly used in a generic way. Safe use information for mixtures is developed for typical uses, compositions and hazard profiles for products within specific sectors. An advantage of this is that a large number of mixtures can be covered by a limited number of generic sets of realistic and consistent safe use information. This information can also be provided in sector-specific terminology.

For options B and C, safe use information for a mixture may be communicated by including it in the main body of the safety data sheet or as an annex.

Challenges identified

Several challenges for the substances' exposure scenario based approach (option B) and the ‘mixture use' based approach (option C) remain:

• The identification of ‘lead' or ‘risk driving' substances is a key step and has been shown to be a practical approach. The boundaries, applicability and feasibility of the various methodologies need further evaluation.
  
  These include the DPD+ methodology*, the CLP+** approach, and the Critical Component Approach*** referred to in ECHA's guidance. Workable tools for accepted methodologies also need to be developed.

• The rules for systematic selection and/or scaling of the operational conditions or risk management measures for the relevant ‘lead or risk driving substances' need to be developed. Experiences have revealed that an adjustment is often necessary when consolidating information. This can be handled by transparent mathematical rules if the underlying assessment is based on tools allowing such simple modifications. Such rules would subsequently allow the information to be automatically processed as far as possible.
   
• Based on the current legal requirements and guidance documents, a formulator performing a chemical safety assessment, either as a registrant or a downstream user, has the obligation to include the exposure scenario for the assessed substances. However, if they are placing substances on the market in mixtures, they may choose to consolidate the safe use information into an annex. A combination of exposure scenarios for substances and annexes for safe use information for the mixture may cause a lot of confusion for the end user and a practical solution is needed for such situations.
   
• If formulators are required to undertake downstream user chemical safety assessments in such circumstances, the preceding situation would arise more often leading to confusion as mentioned before.
   
• Substance exposure scenarios may contain operational conditions or risk management measures that are not derived from quantitative assessments for the specific substance (for example, qualitative assessments, such as being hazardous to the eyes or physico-chemical hazards). Qualitative approaches based on the classification of the mixture are probably needed in such cases. They may also be appropriate when a lead substance exposure scenario is not yet available.

Once several methodologies are broadly used and more experience is gained, additional issues are expected to pop up. It will be quite a challenge for industry to find answers to all of these questions. It will also require a lot of time and effort to train all actors and develop expertise, particularly in smaller companies.

Way forward

Despite all of the efforts that industry is currently putting into this, there is no golden solution. Expert judgment will always be needed to support any approach to determine safe use information for mixtures. Further work will be done in preparation for ENES5 in November and beyond. Detailed discussions during ENES5 and with the stakeholders involved in ECHA's CSA/ES Roadmap action 4.4, are needed to develop workable methodologies for generating useful safe use information for mixtures when communicating down the supply chain.

Further information:

• REACH: Exposure scenarios for preparations, Cefic/DUCC, June 2010
• REACH Practical Guide on Exposure Assessment and Communication in the Supply chains, part 3: Mixtures under REACH, Cefic/VCI, March 2010
• REACH Guidance for downstream users

* Cefic has prepared a methodology based on the Dangerous Preparations Directive (DPD), enhanced for certain health exposure pathways with consideration of the volatility of the substances concerned. It is known as the DPD+ method.

** Work has commenced on converting the DPD+ method to a CLP based method, termed CLP+. This was presented for the first time at ENES4 in May 2013.

***The critical component approach is outlined in ECHA's Guidance for downstream users. It relies on derived no effect levels (DNELs) and predicted no effect concentration (PNEC) for all substances, their concentrations in the mixture and on substance- and use-specific availability parameters indicating their potential for exposure. The critical component approach has not been developed in detail yet. 

Did you know?   According to REACH, there is no obligation to prepare exposure scenarios for mixtures. Exposure scenarios are part of the chemical safety report for individual substances for which an exposure assessment is required.   However, there is an obligation to communicate exposure scenario information for substance components in mixtures down the supply chain. Relevant information from the exposure scenarios for substances should be incorporated when drafting a safety data sheet for a mixture. This typically includes information on the appropriate conditions of use and risk management measures for the various uses of the mixture.

Text by contributors from Cefic, DUCC and Atiel.