MA3 Aquatic Ecotoxicology
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() The risk of PAH phototoactivated toxicity in yellow perch.

Diamond, S1, Mount, D1, Erickson, R1, Hienis, L1, Hockett, J1, Highland, T1, Jenson, C, 1 USEPA/NHEERL/MED, Duluth, MN, USA

ABSTRACT- The risk of phototoactivated toxicity (PAT) of polycyclic aromatic hydrocarbons (PAH) in nature is a product of chemical and ultraviolet radiation (UVR) exposure. In an effort to quantify this risk for yellow perch (Perca flavescens), a PAT laboratory assay was completed and typical water-column depths of perch egg deposition was determined by field survey. UVR penetration for egg locations was determined spectrophotometrically using filtered water samples collected at egg locations. These data provide the means for comparison of laboratory dose-response estimates for PAT with typical field UVR exposure. Ongoing research at a PAH-contaminated site, Stryker Bay, provided estimates PAH exposure. Preliminary response estimates for the assay (LD50 = 372 ugWhr * lcm-2) were based on water concentration and continuous UVR exposure. Egg depths in the wild ranged from 10 cm to 120 cm. Corresponding attenuation of UVR ranged from 48.5 to 99.9 % for these depths in the lowest-attenuating lake. Risk estimation was based on estimates of typical UVR intensities for northern Minnesota (average = 1700 uW * cm-2), assumptions of PAT potential for the mixtures present at Stryker Bay, and water-column attenuation. On a time basis, and for highest potential UVR exposure (10-cm depth), the LD50 would be reached in approximately 2.5 hr. At a depth of 120 cm, the LD50 would not be reached within the embryo period. This was also true at all depths in relatively high-attenuation lakes. At a depth of 10 cm in Stryker Bay, the LD50 would be reached in 21.6 hr. However, assay results indicated that reciprocity of UVR * PAH did not hold for all possible multiples of these two potency factors, suggesting that embryos would be at lower risk in Stryker Bay. The available date provide the means to complete a probabilistic risk assessment; this aspect will be discussed.

Key words: fish, phototoxicity, risk assessment

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