Contemporary Pesticide Usage In The Puget Sound Basin: A Level Of Concern Approach For Evaluating Aquatic Contamination Potential

The Puget Sound basin, a 12-county region near Seattle,WA, contains a diverse economic base in which a wide variety of modem chemicals are used for pest control. Such modern pesticides are seldom included in sampling surveys or monitoring programs because investigators generally are unaware of their potential presence. This study was initiated to fill that information gap. Pesticides currently used in the basin were identified and ranked by a three-tiered level of concern approach. Ranks were based on relative potential to migrate to and endanger the aquatic environment ofpuget Sound. Three major factors were evaluated: estimated amount of pesticide usage in the basin, fate in the environment, and toxicity to nontarget aquatic organisms. Usage Pesticide usage rates were estimated for 20 user categories, using limited surveys, interviews, and, for urban pesticide usage, extrapolation from sources outside the basin. An estimated 2.8 million pounds comprising 120 pesticide active ingredients are used annually in the basin. Major use categories, in rank order, are urban, military, agricultural, transportation-related (i.e., for right-of-ways), and forest-related. Estimated annual usage rates for the major pesticides used in the Puget Sound basin are summarized in the following figure. Estimated Pesticide Usage in the Puget Sound Basin a