Integrating Selection and Risk Assessment of Chemical Mixtures: A Novel Approach Applied to a Breast Milk Survey.

Background: One of the main challenges of modern risk assessment is to account for combined exposure to the multitude of various substances present in food and the environment.
Objective: The present work proposes a methodological approach to perform chemical risk assessment of contaminant mixtures across regulatory silos regarding an extensive range of substances and to do so when comprehensive relevant data concerning the specific effects and modes of action of the mixture components are not available.
Methods: We developed a complete step-by-step approach using statistical methods to prioritize substances involved in combined exposure, and we used a component-based approach to cumulate the risk using dose additivity. The most relevant toxicological end point and the associated reference point were selected from the literature to construct a toxicological threshold for each substance.
Discussion: By applying the proposed method to contaminants in breast milk, we observed that among the 19 substances comprising the selected mixture, ∑ DDT , ∑ PCBi , and arsenic were main joint contributors to the risk of neurodevelopmental and thyroid effects for infants. In addition, ∑ PCCD / F contributed to the thyroid effect and ∑ aldrin-dieldrin to the neurodevelopmental effect. Our case study on contaminants in breast milk demonstrated the importance of crossing regulatory silos when studying mixtures and the importance of identifying risk drivers to regulate the risk related to environmental contamination. Applying this method to another set of data, such as human biomonitoring or in ecotoxicology, will reinforce its relevance for risk assessment. https://doi.org/10.1289/EHP8262.