The Science Is Clear: It Is Time for the EU to Act on Chemical Mixtures in REACH

By Marlene Ågerstrand, Stockholm University, Sweden

We, a group of scientists* dedicated to protecting human and environmental health, recently sent an open letter to the European Commission urging them to follow through on their commitment to introduce a Mixture Assessment Factor in the ongoing REACH revision. This commitment, articulated in the “EU Chemicals Strategy for Sustainability Towards a Toxic-Free Environment,” is scientifically well-founded and critical to addressing a crucial blind spot in chemical regulation: the risks posed by mixtures of chemicals.  

Our position is based on robust and growing scientific evidence: exposure to complex mixtures of chemicals is the norm rather than the exception in the environment and in human populations, and these complex mixtures can cause harm even when individual substances comply with current safety thresholds.

Scientific Consensus on Mixture Effects

Humans and wildlife are continuously exposed to complex chemical cocktails through air, water, food, consumer products and the environment. In 2003, blood tests on former Commissioner Margot Wallström was found to contain 28 out of 77 chemicals analyzed. Since then, systematic human biomonitoring programs, such as HBM4EU, have shown that the general public is continuously exposed to multiple chemicals simultaneously. Similarly, research has found that marine mammals accumulate a variety of legacy and emerging organic pollutants, which interact as mixtures and often surpass regulatory safety thresholds.

A growing body of scientific evidence shows that widespread chemical mixtures have a significant impact on both human health and the environment. For instance, recent studies have reported a decline in male sperm quality, linked high exposure to hazardous chemical mixtures with neurodevelopment risks and IQ losses across different age groups in Europe, and associated mixture exposure with delayed language development, which is an indicator of impaired brain development. In line with this, a recent study has demonstrated that mixture of chemicals present in the blood of European pregnant women were associated with neurotoxic effect, despite each chemical occurring at a “safe” level, i.e., not exceeding regulatory thresholds.

The challenge of chemical mixtures is real, the science is clear, and the time to act is now. In light of this, continuing to evaluate and manage chemicals one at a time leads to a systematic underestimation of risk and subsequently to inadequate protection levels.

Mixture Assessment Factor Is a Suitable Regulatory Tool

The Mixture Assessment Factor is a scientifically grounded tool designed to account for the gap between single-substance assessments and real-world mixture exposures. It introduces an additional safety factor (e.g., a factor of 10), thus providing a buffer to protect against unassessed mixture toxicity. The Mixture Assessment Factor is both implementable and proportional. It is a practical and pragmatic response to deal with the increasing number of new chemicals appearing on the market. The Mixture Assessment Factor can be applied immediately while allowing for refinement as more data become available or when more assessment models are developed. For more information, the Swedish Chemicals Agency commissioned a report outlining an overview of the scientific information for implementing a Mixture Assessment Factor.

The implementation of a Mixture Assessment Factor is backed by the European Parliament, multiple EU member states, and relevant advisory bodies, underscoring strong institutional support for its use.

EU Should Stay on the Initiated Path

The EU Chemicals Strategy for Sustainability recognized mixture effects as one of the key areas to address and explicitly committed to the implementation of a Mixture Assessment Factor. Its implementation would bring REACH into better alignment with both scientific evidence and the precautionary principle, a key pillar in the EU law. Yet despite the clear rationale, scientists are increasingly concerned that political hesitancy may erode this important measure during the REACH revision process.

To set the record straight: No new scientific evidence has emerged that undermines the case for a Mixture Assessment Factor. On the contrary, the evidence in support of it has only grown stronger. Delaying or abandoning the introduction of Mixture Assessment Factor into REACH would be a step backward for chemical safety, public health and environmental protection.

Call to Action

We, the authors of the letter*, call on the European Commission and member states to demonstrate leadership in evidence-based policy and implement a Mixture Assessment Factor in REACH as proposed in the “Chemicals Strategy for Sustainability.” We stand ready to support the implementation of this measure, and we encourage fellow scientists, regulators and stakeholders to join us in advocating for a regulatory framework that reflects the realities of chemical exposure.

Contact: Marlene.Agerstrand@aces.su.se

*Letter written and signed by:

Christina Rudén, Stockholm University, Sweden
Andreas Kortenkamp, Brunel University, UK
Hans Peter H. Arp, NTNU Trondheim & NGI Oslo, Norway
Thomas Backhaus, RWTH University Aachen, Germany
Carl-Gustaf Bornehag, Karlstad University, Sweden
Bethanie Carney Almroth, University of Gothenburg, Sweden
Beate Escher, Helmholtz Centre for Environmental Research–UFZ, Leipzig, Germany and University of Tübingen, Germany
Kathrin Fenner, University of Zürich, Switzerland
Ksenia Groh, Eawag - Swiss Federal Institute of Aquatic Science and Technology, Switzerland
Juliane Hollender, Eawag - Swiss Federal Institute of Aquatic Science and Technology, Switzerland and ETH Zürich, Switzerland
Henner Hollert, Goethe University Frankfurt, Germany
Annika Jahnke, Helmholtz Centre for Environmental Research–UFZ, Leipzig, Germany and RWTH Aachen University, Germany
Olwenn Martin, University College London, UK
Lubica Murinova, Slovak Medical University, Slovakia
Anne-Simone Parent, University of Liège, Belgium
Ad Ragas, Radboud University, The Netherlands
Martin Scheringer, Masaryk University, Brno, Czech Republic, and ETH Zürich, Zürich, Switzerland
Gabriel Sigmund, Wageningen University & Research, the Netherlands
Kristian Syberg, Roskilde University, Denmark
Martin Wagner, Norwegian University of Science and Technology, Norway
Paul van den Brink, Wageningen University & Research, The Netherlands
Marlene Ågerstrand, Stockholm University, Sweden