As mentioned above, when exposed to aqueous solutions of individual PAHs, the range in lethal toxicity can be up to 4 orders of magnitude for a given species over all congeners. This is best shown for aquatic invertebrates (and fish) because of the large amount of mortality data that has been generated. While the concentrations for sublethal responses will be lower, it is not known if this same pattern of variability will hold. For many sublethal responses, specific mechanisms of toxicity are responsible for the effect which may result in differential toxicity among the various PAHs.
A large effort has been applied to determining the concentrations of contaminants in bedded sediment that are toxic to aquatic invertebrates. These are known as sediment quality guidelines, which have been developed for a large number of compounds including individual and total PAHs. A number of methods and approaches have been used and most of these indicate adverse effects to invertebrates at concentrations ranging from 2 to 4 mg total PAH/g dry sediment. These values are intended to be protective of most adverse effects.
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