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Greater Yellowstone Ecosystem Report

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After the sudden emergence of mercury (Hg) poisoning in bald eagles in the Greater Yellowstone Ecosystem in December 2005, we began a preliminary study to investigate if Hg accumulated at toxic levels in wildland firefighters who were exposed to smoke and other particulates while fighting fires in the western United States during summer 2007. Deviating from our original design, we were able to analyze blood from 12 subjects, and repeated blood draws occurred for only four of those subjects. Three of the subjects had measurable Hg levels that approached the limit of a non­toxic Hg concentration (<10 mcg/L). A fourth subject had a measurable level of 4 mcg/L. All other subjects had levels designated by <4 mcg/L. For the four subjects with repeated blood draws, two demonstrated an increase in mercury levels over time (<4 to 7 mcg/L, and 5 to 8 mcg/L), one showed no change over time (<4 to <4 mcg/L), and one demonstrated a decrease in mercury levels over time (4 to <4 mcg/L). Beside Hg, blood analyses were performed for the presence of four other metals: lead, cadmium, cobalt, and thallium. Levels of these metals were well-below toxic thresholds and within normal range for all subjects. Although we recorded times of exposure to smoke for all subjects, our sample was too small to investigate any statistical inference about the relationship between the duration of exposure to smoke and changes in blood Hg concentration. As forest fires continue to ignite in the western U.S. at unprecedented levels, burning areas such as dried bogs and marshes, we highly recommend continued research and a mercury­monitoring program to ensure the continued health and safety of our firefighting crews.