The European Union stands ready to revise its Reach (Registration, Evaluation, Authorisation, and Restriction of Chemicals) regulations, with a sharp emphasis on the growing concern surrounding ‘chemical cocktails’ present in both the environment and the human body. Historically, chemical regulations have dealt with substances on a case-by-case basis, requiring manufacturers to prove their safe usage at environmental concentrations. However, this approach fails to acknowledge the intricate realities of chemical mixtures and the risks they entail.
Professor Thomas Backhaus, acclaimed for his expertise in ecotoxicology at RWTH University Aachen, advocates for a revolutionary strategy through the introduction of the mixture allocation factor. This novel measure aims to address the reality of chemical mixtures by capping the cumulative risk any individual chemical can add to the overall exposure.
Currently, risk is evaluated based on the ratio of a chemical’s presence to its toxicity, forming a risk quotient that must not surpass one. This guarantees that chemical concentrations do not exceed the calculated safe levels. The suggested framework shifts from this paradigm by conceptualizing the entire environment as a single risk entity or “risk cup”, where the combined risk quotient of all chemicals must not exceed one. The innovation of the mixture allocation factor effectively lowers the allowable risk contribution of individual chemicals, establishing a more stringent threshold below one.
For example, implementing a mixture allocation factor of five decreases the acceptable risk quotient from 1 to 0.2 for each chemical. When assessing risk quotients under this framework, evaluations are focused on comparing to this more conservative figure. This method enables regulators to quickly pinpoint and address “risk driver” chemicals that significantly influence the overall risk, while less significant chemicals remain largely unaffected.
This suggested framework is adaptable, suitable for various sample types without the need for new data collection techniques. Backhaus notes that although numerical differences may arise from diverse chemical compositions in human bodies and environmental samples, the underlying principles stay constant.
In spite of its potential, experts like Cynthia Rider from the National Institute of Environmental Health Sciences express a cautious optimism. The effectiveness of the mixture allocation factor will only be evident once it is implemented and put to the test in real-world situations. Likewise, Claus Svendsen of the UK Centre for Ecology & Hydrology points out the difficulty in determining which chemicals should be included in mixture assessments, indicating that categories like pesticides and pharmaceuticals may require distinct allocation factors due to their specific biological effects.
Backhaus acknowledges that although industrial chemicals, which number many but are not necessarily the most hazardous, should be prioritized initially, the system will need adjustments as more detailed data becomes available regarding the diversity and levels of concurrent chemical exposures in the environment. This approach represents an essential first step toward a comprehensive and potentially more protective chemical regulation framework within the EU.