Abstract
Current chemicals regulation operates almost exclusively on a chemical-by-chemical basis, however there is concern that this approach may not be sufficiently protective if two or more chemicals have the same toxic effect. Humans are indisputably exposed to more than one chemical at a time, for example to the multiple chemicals found in food, air and drinking water, and in household and consumer products, and in cosmetics. Assessment of cumulative risk to human health and/or the environment from multiple chemicals and routes can be done in a mixture risk assessment (MRA). Whilst there is a broad consensus on the basic science of mixture toxicology, the path to regulatory implementation of MRA within chemical risk assessment is less clear.In this discussion piece we pose an open question: should the scope of human MRA cross legislative remits or ‘silos’? We define silos as, for instance, legislation that defines risk assessment practice for a subset of chemicals, usually on the basis of substance/product, media or process orientation. Currently any form of legal mandate for human MRA in the EU is limited to only a few pieces of legislation. We describe two lines of evidence, illustrated with selected examples, that are particularly pertinent to this question: 1) evidence that mixture effects have been shown for chemicals regulated in different silos and 2) evidence that humans are co-exposed to chemicals from different silos. We substantiate the position that, because there is no reason why chemicals allocated to specific regulatory silos would have non-overlapping risk profiles, then there is also no reason to expect that MRA limited only to chemicals within one silo can fully capture the risk that may be present to human consumers. Finally, we discuss possible options for implementation of MRA and we hope to prompt wider discussion of this issue.
Highlights
Introduction and backgroundThe current approach to chemical regulation routinely depends on assessment on a chemical-by-chemical basis, there is concern that this approach may not be sufficiently protective if two or more chemicals have the same toxic effect on humans (Boobis et al, 2008; Kortenkamp et al, 2009)
We describe two lines of evidence, illustrated with selected examples, that are pertinent to this question: 1) evidence that mixture effects have been shown for chemicals regulated in different silos and 2) evidence that humans are co-exposed to chemicals from different silos
We have presented two lines of evidence; firstly, that mixture effects have been observed and can be expected for chemicals that are regulated in different ‘silos’ and secondly, that humans are exposed to chemicals from different silos, and chemicals from different silos can be detected in human tissues
Summary
The current approach to chemical regulation routinely depends on assessment on a chemical-by-chemical basis, there is concern that this approach may not be sufficiently protective if two or more chemicals have the same toxic effect on humans (Boobis et al, 2008; Kortenkamp et al, 2009). Under EU law, the only notable exception to the chemicalby-chemical paradigm is the Toxic Equivalency Quotient/Factor (TEQ/ TEF) approach (van den Berg et al, 1998) in which dioxin-like chemicals, including selected polychlorinated biphenyls, dioxins and furans, are assessed collectively in regulations concerning maximum limits in food items (Regulation EC No 1881/2006 on setting maximum levels for certain contaminants in food) This approach, as conceived, is limited to the risk assessment of a particular set of compounds (halogenated aromatic hydrocarbons) with a particular property (toxicological similarity to dioxin as manifested by AhR activation). The German Federal Institute for Risk Assessment (BfR) have drafted a concept for how to take account of cumulative aspects in the context of the regulation of plant protection products and biocides (Stein et al, 2014) In this discussion piece we pose an open question: should the scope of human mixture risk assessment (MRA) cross legislative remits? We substantiate the position that, because there is no reason why chemicals allocated to specific regulatory silos would have non-overlapping risk profiles, there is no reason to expect that MRA limited only to chemicals within one silo can fully capture the risk that may be present to human consumers
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