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6.3.1 Petroleum related components Crude oil

Approximately 56 studies have been conducted with crude oil.  There have been a number of different oil types included in the different testing programs, as well as different types of preparations with untreated (soluble fraction or physically dispersed) or treated oil (chemical dispersant or ISB). Peer-reviewed studies with photochemically enhanced toxicity (photooxidation) with Arctic species are not available. However, photoenhanced toxicity of physically and chemically dispersed Alaska North Slope crude oil has been evaluated with Pacific herring eggs and larvae (Clupea pallasi; Barron et al. 2003). 

Exposure systems vary between studies although there is an increasing trend to harmonize the approaches between laboratories.  Studies have been conducted as continuous or declining exposures, with WAF, dispersed WAF, or physical dispersions.  It is noteworthy that relatively few types of chemical dispersants have been used in toxicity studies, primarily Corexit®9500 and Dasic Slickgone. The vast majority of the exposures were waterborne and five studies were diet borne exposures.

Relatively few studies have included weathered oil.  There are some studies (e.g. Hansen et al. (in prep) have tested weathered and unweathered oil with the copepod C. finmarchicus. Given that OSR response times may be delayed in the Arctic due to the potential distances and inclement weather, this should be a future focus of study. Single PAH

Single PAH toxicity data are an important component in developing predictive models and for comparing effects between different OSR alternatives.  Most studies performed with single compounds included 2-methyl naphthalene, naphthalene, and pyrene.  Fewer studies have evaluated benzo(a)pyrene and phenanthrene and primarily when evaluating uptake and tissue residues.  The naphthalene compounds are often included in testing programs since they are predominant in the crude oil and are known to elicit most of the acute toxicity.  Pyrene and benzo(a)pyrene have been used as model compounds to study a specific biological mechanism (uptake rate, metabolism, enzyme induction).