A new approach to protect people and nature from the hidden risks of chemical cocktails

Every day, people and organisms in the environment are potentially exposed to dozens or even hundreds of chemicals, from plastics and pesticides to cosmetics and cleaning agents.

While each chemical may individually meet safety standards, their combined effects can quietly add up. A new policy brief published in Science argues that current chemical regulations fail to reflect this reality and systematically underestimate the risks from these "chemical cocktails."

The authors call on European policymakers to take a decisive step: integrate a Mixture Allocation Factor (MAF) into the upcoming revision of the EU's REACH Regulation, which governs the registration, evaluation, and authorization of chemicals.

"Chemical safety cannot be guaranteed by assessing substances one by one," explains lead author Professor Thomas Backhaus, Chair of Ecotoxicology and Environmental Risk Assessment at RWTH Aachen University and an affiliate professor at the University of Gothenburg. "We urgently need a system that acknowledges that we live in the presence of complex mixtures."

Why Mixtures Matter

Research shows that mixtures of chemicals, even when each is present below its regulatory limit, can still harm health and ecosystems. The combined exposure can exceed what scientists call the "safe space." Studies on reproductive disorders, for example, reveal that real-world mixtures of pesticides and plasticizers can cause developmental damage in animals at levels far below official thresholds. Similar evidence has been accumulating in environmental research, where pollutants have been shown to interact in complex but predictable ways.

The team of authors points out that the concentration addition principle, long used for dioxin-like pollutants, is a scientifically proven way to estimate the combined effects of multiple chemicals. Ignoring mixture toxicity, they argue, contradicts both empirical evidence and basic biology: cells and organs do not act in isolation and neither do chemicals.

The Mixture Allocation Factor

To translate this insight into policy, the authors propose the Mixture Allocation Factor. The idea is simple: each chemical occupies a fraction of an overall "risk cup." The cup represents the total amount of chemical pressure that humans or ecosystems can safely tolerate. By adjusting the fraction that each substance may contribute, regulators can ensure the cup never overflows.

Importantly, the MAF would not penalize manufacturers of low-risk chemicals. Only those substances that dominate the risk would face stricter control measures or emission reductions. This targeted approach would enable more realistic protection without overwhelming bureaucracy.

A Pragmatic Step Forward

The European Commission's Chemicals Strategy for Sustainability has already recognized the need for such a mechanism, and several EU Member States-including Sweden, Denmark, Finland, and Luxembourg-support the inclusion of a MAF in REACH. The authors suggest starting with a moderate MAF value (for example, 5) and refining it as new data emerge.

Adopting the MAF would, Backhaus and colleagues argue, make EU chemical regulation more science-based and future-proof-aligning it with the same logic already used to compare greenhouse gases via CO₂ equivalents. "It's time chemical risk management catches up with what biology and environmental science have long shown," Backhaus says. "A more mixture-aware REACH would improve the protection of both human health as well as the environment, while supporting innovation in the chemical industry."

» Original publication

Source: RWTH Aachen University