title: Application of the maximum cumulative ratio (MCR) as a screening tool for the evaluation of mixtures in residential indoor air.
abstract: The maximum cumulative ratio (MCR) method allows the categorisation of mixtures according to whether the mixture is of concern for toxicity and if so whether this is driven by one substance or multiple substances. The aim of the present study was to explore, by application of the MCR approach, whether health risks due to indoor air pollution are dominated by one substance or are due to concurrent exposure to various substances. Analysis was undertaken on monitoring data of four European indoor studies (giving five datasets), involving 1800 records of indoor air or personal exposure. Application of the MCR methodology requires knowledge of the concentrations of chemicals in a mixture together with health-based reference values for those chemicals. For this evaluation, single substance health-based reference values (RVs) were selected through a structured review process. The MCR analysis found high variability in the proportion of samples of concern for mixture toxicity. The fraction of samples in these groups of concern varied from 2% (Flemish schools) to 77% (EXPOLIS, Basel, indoor), the variation being due not only to the variation in indoor air contaminant levels across the studies but also to other factors such as differences in number and type of substances monitored, analytical performance, and choice of RVs. However, in 4 out of the 5 datasets, a considerable proportion of cases were found where a chemical-by-chemical approach failed to identify the need for the investigation of combined risk assessment. Although the MCR methodology applied in the current study provides no consideration of commonality of endpoints, it provides a tool for discrimination between those mixtures requiring further combined risk assessment and those for which a single-substance assessment is sufficient.
authors.affiliation: Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium. Electronic address: katleen.debrouwere@vito.be.
authors.forename: Katleen
authors.initials: K
authors.lastname: De Brouwere
authors.affiliation: Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium.
authors.forename: Christa
authors.initials: C
authors.lastname: Cornelis
authors.affiliation: Karlsruhe Institute of Technology, Kreuzeckbahn Straβe 19, 82467 Garmisch-Partenkirchen, Germany.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Arvanitis
authors.affiliation: Cranfield University, Institute of Environment and Health, Cranfield, UK.
authors.forename: Terry
authors.initials: T
authors.lastname: Brown
authors.affiliation: Cranfield University, Institute of Environment and Health, Cranfield, UK.
authors.forename: Derrick
authors.initials: D
authors.lastname: Crump
authors.affiliation: Cranfield University, Institute of Environment and Health, Cranfield, UK.
authors.forename: Paul
authors.initials: P
authors.lastname: Harrison
authors.affiliation: National Institute for Health and Welfare (THL), P.O. Box 95, 70701 Kuopio, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Jantunen
authors.affiliation: The Dow Chemical Company, 1803 Building, Midland, MI, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Price
authors.affiliation: Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium.
authors.forename: Rudi
authors.initials: R
authors.lastname: Torfs
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D016902:Air Pollution, Indoor / Q000032:analysis / Q000706:statistics & numerical data*; D004784:Environmental Monitoring / Q000379:methods*; D006798:Housing / Q000706:statistics & numerical data; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis / Q000706:statistics & numerical data; D018570:Risk Assessment
chemical_list: D000393:Air Pollutants
keywords: Combined risk assessment; EXPOLIS; Multiple substances; Non-cancer endpoints; OQAI; Screening tool