Setting Rational Health-Related Water Quality Standards for Dioxin - Risk Assessment for the Columbia River, 1990 Environmental Conference Proceedings

Consumption of Columbia River fish does not present a significant health risk to sensitive groups or to the general population of the Pacific Northwest. For the typically exposed individual. the potential dioxin intake from eating Columbia River fish is estimated to be significantly less than the average daily intake from all dietary sources. For sportsfishermen, the most sensitive population examined in this risk assessment, potential dioxin intake via ingestion of Columbia River fish is no greater than the intake incurred by the general U.S. population through fish consumption. Carcinogenic health risks related to the ingestion of Columbia river fish are well below de minimis risk levels. It is likely that a portion of the dioxin found in the sampled fish came from-sources-on the Columbia River other than that of the paper mills’ final effluent. Consequently, a portion of the range of potential cancer risks estimated in this analysis should be attributed to sources other than the NWPPA paper mills. It is the opinion of ChemRiskTM that the results of this risk assessment do not indicate that regulatory action is needed to protect the health of Columbia River Basin residents.

Since state regulatory agencies are required to establish ambient water quality standards for TCDD by 1992, it is imperative that standards be based on the most current scientific and site-specific information available. Based on site-specific exposure data and a scientifically-defensible cancer potency factor, ChemRisk recommends 1.6 to 14 ppq (pg/L) as an appropriate ambient water quality criteria for TCDD in the Columbia River, protective of human health.