1. Summary of the report of the chief scientific group
This joint report from the Environment Agency and the UK Health Safety Agency identifies a recommended approach to addressing the environmental and human health risks of unintentional mixing of chemicals under the UK REACH Regulation (registration, evaluation, authorization and restriction of chemicals). This work is important to inform future updates to UK REACH.
There is international agreement that exposure to mixtures of chemicals can cause harmful effects to both people and the environment, even when the chemicals individually are below levels of concern. This may be the result of additive effects, for example. However, the current risk assessment approach under UK REACH considers chemicals in isolation as it applies to the manufacture and use of separate registered substances. We therefore wanted to examine how the potential risk of unintentional mixtures (such as may form following the release of the registered substance into the environment) could be integrated into the risk assessment approach for industrial chemicals. .
We have summarized the different methods available to estimate the risk of mixtures and reviewed studies that have estimated the potential toxicity of mixtures based on measured chemical concentrations. We looked at the pros and cons of different methods that can be used to assess the risks of unintentional mixtures.
We have found that it is virtually impossible to identify in advance which specific substances have the potential to contribute most to the risk of admixture, as this varies across specific sites, times, and populations studied. For this reason, applying a mixture assessment factor (MAF) in risk assessment calculations is a pragmatic way forward. A MAF is an additional ‘safety factor’, which can either be used to derive ‘acceptable’ thresholds based on (eco)toxicity data, or applied to the risk characterization report (where an exposure concentration predicted or measured is divided by the threshold acceptable concentration). Either way, it would make the risk assessment more conservative because it would add an extra level of precaution.
Alternative approaches to a MAF require additional data and resources before they can be applied, and the use of a MAF would retain the principle that it is the responsibility of the UK REACH registrant to demonstrate that the risks are adequately controlled. For the environment, a MAF of 5 seems appropriate and protective for most surface waters. For human health, it is not considered appropriate to apply a MAF at this time.
1.4 Next steps
Our report focused on the scientific considerations of how the potential risk from unintentional mixtures could be addressed under UK REACH. We will continue to provide advice to the Department of Environment, Food and Rural Affairs and other government agencies as they consider whether any changes need to be made to the current risk assessment approach.
1.5 Posting details
This summary relates to the information reported in detail in the following output:
- Title: Assessment of potential unintentional mixture risk assessment approaches for future UK REACH assessments
- Project leader: Claire Massey, Chemicals Evaluation Unit, Chief Scientific Panel
- Research contractor: Environment Agency and UK Health Safety Agency
This project has been published by the Environment Agency’s Chief Science Group, which provides scientific knowledge, tools and techniques to enable us to protect and manage the environment as effectively as possible.
Information: [email protected]
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