Risk assessment for dioxin in Columbia River fish

Abstract

The Columbia River, located in the Northwestern United States, supports active commercial and recreational fisheries. In addition to other industries, a number of bleached kraft pulp and paper mills are located along the river in the States of Washington and Oregon. To determine the impact that effluents from these mills have on residue levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in fish, the most extensive field survey and health risk assessment ever conducted on a major river was undertaken. A total of 680 fish, including anadromous (salmon and steelhead trout) and resident (white sturgeon, carp, and largescale sucker) species were collected at 6 sampling stations located upstream and downstream of the mills. Eighty percent of the anadromous fish and 45% of all fish sampled had no detectable levels of TCDD. The geometric mean concentrations in fillet tissues of 3 subspecies of salmon ranged from 0.08 to 0.31 ppt; steelhead trout averaged 0.07 ppt. White sturgeon, largescale sucker, and carp collected in reaches impacted by mills averaged 0.55, 0.30, and 1.07 ppt, respectively, while fish collected upstream averaged 1.12, 0.24, and 1.12 ppt, respectively. These data indicate that mill effluents did not elevate fish TCDD residues above background. Lifetime average daily doses (LADDs) for residents, recreational fishermen, Asian Americans, and Native Americans were 0.0034, 0.056, 0.013, and 0.024 pg/kg-day. The theoretical upper-bound excess lifetime cancer risks associated with the consumption of Columbia River fish by recreational fishermen, the most sensitive consumers examined in this analysis, was below one in one million (5 × 10 −7).