PAH Checklist

• Widespread in the estuary, both geographically and in the food chain
• Released through combustion or spill of gasoline, diesel fuel, and other petroleum products; possible releases from marine pilings
• Metabolized by fish, birds, and people, but metabolites can be harmful
• High molecular weight PAHs more toxic and persistent than low molecular weight PAHs

What Are They?

Polycyclic aromatic hydrocarbons, or PAHs, are widespread organic contaminants that are released through the combustion or spill of gasoline, diesel fuel, and other petroleum products. They also are created through the incomplete combustion of carbon-containing materials such as wood, coal, and tobacco. PAHs are used in manufacturing dyes, insecticides, and solvents, and they are a constituent of the creosote found in railroad ties and marine pilings.

PAHs often attach to soil and sediment. They bioaccumulate in invertebrates but are metabolized by fish, birds, wildlife, and people. However, in the process, some metabolites can be more harmful than the original compounds and can generate mutations, be carcinogenic, or cause cell death.

PAHs fall into two groups, depending on their molecular weight. Low molecular weight PAHs are less toxic and less persistent than high molecular weight PAHs, and more likely to dissolve in water.

PAHs in the Estuary

PAHs have been found in river water samples and in the bile and stomach contents of juvenile salmon from sites throughout the Columbia River estuary, from just below Bonneville Dam to the river’s mouth near Astoria (Lower Columbia River Estuary Partnership 2007).

Impacts in the Environment

Exposure to PAHs can impair salmon growth, cause physical or developmental abnormalities, reduce disease resistance, and disrupt reproduction.

PAH concentrations in some juvenile salmon in the estuary are high enough (7,000 nanograms per gram wet weight) to be of concern. This level has been associated with altered immune system function, growth, blood chemistry, and fatty acid profiles.

Sources of Exposure

Common sources of PAHs are vehicle exhaust, coal tar, and municipal or industrial activities that involve combustion. In aquatic environments, marine pilings may also be a source of PAHs. High molecular weight PAHs enter rivers and streams through atmospheric deposition and stormwater runoff. Low molecular weight PAHs are more likely to enter the environment from incidental spills of gasoline and diesel fuel.

PAHs can be found in the soil, sediment, air, and water, and in invertebrate species.

In the Columbia River estuary, juvenile salmon are exposed to PAHs through their prey and river water (Lower Columbia River Estuary Partnership

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ⁱ Lower Columbia River Estuary Partnership. 2007. Lower Columbia River and Estuary Ecosystem Monitoring: Water Quality and Salmon Sampling Report.

ⁱⁱ Arkoosh, M.R., E. Casillas, E. Clemons, B. McCain, and U. Varanasi. 1991. Suppression of Immunological Memory in Juvenile Chinook Salmon (Oncorhynchus tshawytscha) from an Urban Estuary. Fish & Shellfish Immunology, 1:261-277.

ⁱⁱⁱArkoosh, M.R, E. Casillas, P. Huffman, E. Clemons, J. Evered, J.E. Stein, and U. Varanasi.
1998. Increased Susceptibility of Juvenile Chinook Salmon (Oncorhynchus tshawytscha) from a Contaminated Estuary to the Pathogen Vibrio anguillarum. Transactions of the American Fisheries Society, 127:360-374.

^iv Casillas, E., M.R. Arkoosh, E.R. Clemons, T. Hom, D. Misitano, T.K. Collier, J.E. Stein, U. Varanasi. 1995. Chemical Contaminant Exposure and Physiological Effects in Outmigrant Juvenile Chinook Salmon from Urban Estuaries of Puget Sound, Washington. Pages 657-665 in Proceedings Puget Sound Research ‘95. Puget Sound Action Team, Olympia, WA.

^v Casillas, E., B-T. L. Eberhart, F.C. Sommers, T.K. Collier, M.M. Krahn, and J.E. Stein. 1998. Effects of Chemical Contaminants from the Hylebos Waterway on growth of Juvenile Chinook Salmon. Interpretive report prepared for NOAA Damage Assessment Center.

^vi Meador, J.P., F.C. Sommers, G.M. Ylitalo, C.A. Sloan. 2006. Altered Growth and Related Physiological Responses in Juvenile Chinook Salmon (Oncorhynchus tshawytscha) from Dietary Exposure to Polycyclic Aromatic Hydrocarbons (PAHs). Canadian Journal of Fisheries and Aquatic Sciences, 63:2364-2376.

^vii Lower Columbia River Estuary Partnership. 2007. Lower Columbia River and Estuary Ecosystem Monitoring: Water Quality and Salmon Sampling Report.