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MA1 Methods in Risk Analysis
(002) Risk assessment of complex mixtures: Gasoline as an example.
Foster, K1, Parkerton, T2, Mackay, D1, 1 Canadian Environmental Modelling Centre, Trent University, Peterborough, Ontario, Canada2 ExxonMobil Biomedical Sciences, Annandale, NJ, USA
ABSTRACT- Many commercial products such as gasoline are complex mixtures comprised of multiple constituents with widely varying properties. It is thus impossible to elucidate environmental exposure by assuming such mixtures behave as a single substance. An approach is suggested and illustrated by which the complex substance is treated as a number of pseudo-components and specifically in the case of gasoline as 24 "hydrocarbon blocks" that are evaluated independently. Selection of blocks is discussed and the required property data are described. A four stage process is outlined: (1) identification of blocks and acquisition of property and composition data; (2) modelling to predict fate and estimate concentrations of exposures for each block, preferably on a unit-emission basis yielding an exposure matrix; (3) combination of the model results to treat actual emission rates and the mixture as a whole and (4) final evaluation of risk. It is concluded that the "hydrocarbon block" approach provides a feasible and credible method to support environmental risk assessment for complex mixtures.
Key words: risk, gasoline, mixtures, hydrocarbon
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