Characterization of mixtures, assessment of exposures, and linkage of exposures to health effects are the objectives of the recommendations proposed for further research.
Even if we assume that the mixture assessment concept of independent action is applicable to the multitude of chemicals relevant to human exposures, certain risks may arise from small effects associated with single chemicals which might cumulate according to stochastic principles.
From the available evidence[6], it is to be expected that the application of CA to a mixture of not entirely similarly acting compounds will lead to a slightly cautious mixture assessment (slight overestimation of risk).
This evaluation considers an extensive suite of sediment chemistry totaling 274 analytes (polycyclic aromatic hydrocarbons, organochlorine compounds, polychlorinated biphenyls, polybrominated diphenyl ethers, trace elements, and current-use pesticides) and a mixture assessment based on the ratios of detected compounds to available effects-based benchmarks.
applying a specific mixture assessment factor (MAF), direct biotesting of the whole product or the environmental mixture resulting from the use of the product, drawing conclusions from available data from similar products (so-called "bridging"), and.
Recently, the introduction of appropriate mixture assessment approaches was forwarded as a regulatory need, with a proposal to use a default model for assessing aggregated responses for a set of chemicals when more specific approaches still lack implementation [10].
Hence, an MCR could enable a yes/no decision on the relevance of a mixture assessment as such, but does not provide criteria to decide which components need to be taken into account in a CBA.
These controls relate prior knowledge of individual components to a complex mixture, allowing assessment of measurement performance.
The issue is linked to the general problem of defining "similar action" for purposes of mixture assessments, but unfortunately there are currently no unambiguous criteria for what should constitute similar action (Mileson et al. 1998).
These guidelines highlight the current practice of mixtures assessment, which relies primarily on the existing single-chemical database.
