Kombinationseffekter av föroreningar (pdf 385 kB) - Naturvårdsverket

English summary
SWECO VIAK
Kombinationseffekter av föroreningar
This report addresses the challenges associated with the calculation of the toxicity of
mixtures of chemicals and the estimation of environmental and health risks of those mixtures.
It is obvious that practical limitations precludes toxicity testing of all possible combinations of
chemicals and concentrations – for instance, testing the toxicity of all combinations of only 10
individual chemicals would require at least 1000 separate assays. As an alternative, the
evaluation of mixture toxicity and risk is based on mathematical and statistical modelling.
The reader is introduced to the most common models to classify and calculate mixture
toxicity. Included are models assuming that 1) the chemicals act independently of each other
in the organisms; 2) the chemicals have the same mechanism of toxicity, affect the same
endpoint, or have the same chemical structure; 3) the chemicals interact with each other in
synergistic or antagonistic ways. Physiologically based pharmacokinetic (PBPK) models
describing metabolism and toxicity of mixtures are briefly presented, and new approaches to
use quantitative structure-activity relationships (QSAR) to estimate toxicity of mixtures from
predicted chemical characteristics of the mixtures are reviewed. Reviews of the scientific
literature shows that the toxicity of 75-80 % of known mixtures of two to four chemicals can
be safely calculated by concentration addition, which means that the contribution of each
component to the mixture toxicity is proportional to its concentration in the mixture.
Schematic decision trees are constructed in the report to help the assessor to evaluate the
toxicity and risk of complex mixtures of more or less unknown composition. Whole mixture
toxicity test at different concentrations is the simplest approach, although sometimes
cumbersome if one or several components are very toxic. Mixtures can be fractionated
based on successive bioassays, fractionated and recombined, fractionated in combination
with identification and toxicity testing of the 10 most risky components, and chemically
identified in combination with a multivariate effects analysis. Since the number of complex
mixtures in the environment is just formidable, the report reviews efforts to develop criteria to
prioritise among them and presents list of prioritised mixtures containing similar components,
mixtures of known and predictable composition, and mixtures of occasional composition or
appearance.
The environmental and health risk of mixtures is often expressed by an index by which the
exposure to an individual component is compared to a guideline or regulatory value of the
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