Risk of unintentional co-exposures

The traditional method of regulating chemicals on a chemical-by-chemical basis has led to a focus on individual chemical exposure in risk assessment procedures. However, with increasing recognition of the potential risks associated with exposure to a cocktail of chemicals, there is a growing need for a more holistic approach.

The EU's Chemical Strategy for Sustainability, published in October 2020, advocates for the integration of combined exposure (i.e., exposure to unintentional mixtures of chemicals from our environment or surroundings or) into chemical risk assessments.

New research provides evidence for policy making on unintentional co-exposures (mixtures of chemicals) to humans and the environment!

ARCHE Consulting is dedicated to advancing scientific understanding of risks associated with co-exposure to chemicals in the environment and human populations. We have actively participated in various studies on this important topic, providing valuable insights and input to ongoing discussions on the most effective method for assessing mixture chemical risk, specifically the Mixture Assessment Factor (MAF).

ARCHE Consulting has been involved the following studies:

Characterising chemical co-exposures in EU to support a combined exposure assessment strategy.

In collaboration with VITO, we analyzed environmental monitoring and human biomonitoring data to gain a deeper understanding of realistic co-exposure to chemicals and evaluate associated risks. Our findings revealed that mixtures in the environment are largely influenced by spatial processes, with complexity increasing from upstream to downstream and under high anthropogenic pressure. Our mixture pressure analysis indicated that the majority of observed mixture exposures do not pose a risk to the environment (81-94% of observed mixtures). For the remaining cases, combined exposure risk estimates are dominated by a few substances and heavily dependent on local factors. We were able to determine which EU Regulations or Directives would be most effective in managing these mixtures of concern. Our research concludes that a potential Mixture Assessment Factor (MAF) should be proportional to the magnitude of the identified mixture toxicity problem. For human exposure, only a small number of compounds are typically covered in monitoring studies, making it difficult to evaluate co-exposure patterns. While it is hard to draw robust conclusions because of the diversity in existing mixture risk studies, the available studies suggest that a small number of compounds tend to drive toxicity.

For more information, please download the final report below and review the technical annexes A-D (environment) and technical annex E (human).

Comparison of MAF methods applied to environmental monitoring data.

Four different published MAF calculation methods were evaluated using freshwater monitoring data from 5 datasets. The robustness of each method was analyzed in terms of: (1) the choice of reference value (i.e. PNEC or HC5); (2) sample size and the presence of unknown and non-detected substances; (3) the consideration of mixtures with single substance risk and (4) the choice of protection level and level of conservatism. Which method takes preference is partly a policy decision, but analyses like these help inform the decision-making. Based on the set of criteria, the Maximum Cumulative Ratio method was found to be the most robust and reliable.

The assessment suggests that in a reasonable worst-case (ca. 90th percentile), a factor of 3 is sufficient to eliminate exposure concerns in most cases, but it is important to note that there can be significant differences between MAF methods. Therefore, future MAF calculations should use a robust method that takes these differences into account. The choice of method is partly a policy decision, but studies like this help inform the decision-making process.

Both studies were commissioned by CEFIC, the European Chemical Industry Council.

Request download permission