title: Should the scope of human mixture risk assessment span legislative/regulatory silos for chemicals?
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.
authors.affiliation: Institute of Environment, Health and Societies, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, UK. Electronic address: richard.evans@brunel.ac.uk.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Evans
authors.affiliation: Institute of Environment, Health and Societies, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, UK. Electronic address: olwenn.martin@brunel.ac.uk.
authors.forename: Olwenn V
authors.initials: OV
authors.lastname: Martin
authors.affiliation: Faust and Backhaus Environmental Consulting, Bremen, Germany. Electronic address: faust@fb-envico.com.
authors.forename: Michael
authors.initials: M
authors.lastname: Faust
authors.affiliation: Institute of Environment, Health and Societies, Brunel University London, Kingston Lane, Uxbridge, Middlesex UB8 3PH, UK. Electronic address: andreas.kortenkamp@brunel.ac.uk.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kortenkamp
mesh_terms: D045424:Complex Mixtures / Q000592:standards / Q000633:toxicity; D004781:Environmental Exposure / Q000331:legislation & jurisprudence* / Q000706:statistics & numerical data; D058735:Environmental Policy; D004785:Environmental Pollutants / Q000592:standards / Q000633:toxicity*; D004787:Environmental Pollution / Q000331:legislation & jurisprudence* / Q000706:statistics & numerical data; D005062:European Union; D006801:Humans; D018570:Risk Assessment
chemical_list: D045424:Complex Mixtures; D004785:Environmental Pollutants
keywords: Chemical toxicity; Chemicals regulation; Human health; Mixture risk assessment; Mixture toxicity; Risk assessment