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Environmental fate & pathways

Additional information on environmental fate and behaviour

Administrative data

additional information on environmental fate and behaviour
Type of information:
calculation (if not (Q)SAR)
Adequacy of study:
other information
Study period:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
accepted calculation method

Data source

Reference Type:
Application of the maximum cumulative ratio (MCR) as a screening tool for the evaluation of mixtures in residential indoor air
Katleen De Brouwere a,⁎, Christa Cornelis a,⁎, Athanasios Arvanitis b, Terry Brown c, Derrick Crump c, Paul Harrison c, Matti Jantunen d, Paul Price e, Rudi Torfs
Bibliographic source:
Science of the Total Environment 479–480 (2014) 267–276
Report date:

Materials and methods

Test guideline
no guideline followed
Principles of method if other than guideline:
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.
GLP compliance:
Type of study / information:
The maximum cumulative ratio (MCR) method

Test material

Constituent 1
Chemical structure
Reference substance name:
2-methoxy-1-methylethyl acetate
EC Number:
EC Name:
2-methoxy-1-methylethyl acetate
Cas Number:
Molecular formula:
2-methoxy-1-methylethyl acetate

Results and discussion

Any other information on results incl. tables

See "Attached Full Study Report" for details on results and discussion.

Applicant's summary and conclusion

This work demonstrates the usefulness ofMCR as a screening tool for identifying indoor airmixtures requiring further assessment of combined exposure. For those identified mixtures, higher tier assessment could involve considering communalities in endpoints, target organs,mode of action affected by the various substances present in the mixtures. Ideally, classification of mixtures should be based on MCR calculations using datasets that contain all compoundswith a potential significant contribution to the MCR. This highlights the need for a comprehensive, harmonized and common set of substances in pan-European IAQ monitoring surveys as further discussed by Crump et al. (2013).
Further challenges in unravelling the issue of mixture toxicity in indoor air are i) the generation of indoor air databases that are optimal for the assessment ofmixture toxicity and include an appropriate target list of substances determined with a sufficiently low limit of quantification, ii) identification of relationships between indoor sources and groups of substances with a substantial contribution to MCR, and iii) investigation of interactions between pollutants in indoor air, including chemical reactions occurring in the indoor air.
Supplementary data to this article can be found in the "Attachment" Section.
Executive summary:

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 theMCR 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 from2% (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 theMCR 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.