Health hazard evaluation report: HETA-99-0173-2856, U.S. Park Service, Turnbull National Wildlife Refuge, Cheney, Washington.
In April 1999, the U.S. Park Service, Turnbull National Wildlife Refuge (TNWR), Cheney, Washington, asked NIOSH to evaluate exposure to chainsaw exhaust among forestry workers. Although workers had not reported any symptoms related to chainsaw exhaust, management wanted to have some documentation of their exposure. Six to eight foresters are employed to thin the forest of pine trees up to 22 inches in diameter. Exposure to airborne carbon monoxide (CO), benzene, aldehydes, and polynuclear aromatic hydrocarbons (PNAs) was evaluated during four days of sampling with wind conditions ranging from calm to 11 miles per hour (mph). Also, carboxyhemoglobin (COHb) levels in each forester were estimated by measuring CO in exhaled breath. On two days of cutting larger trees during light wind conditions (up to 7 mph), full-shift exposure to CO ranged from 8 to 31 parts per million (ppm), with 40% of the exposures exceeding the most protective evaluation criterion of 25 ppm. Peak CO exposures (up to 1100 ppm) were found to occur primarily when foresters were bent or kneeling to cut the stumps of larger trees close to ground level. Estimated COHb levels ranged up to 4.9% with 33% of COHb levels exceeding the evaluation criterion of 3.5%. On two days of cutting smaller trees during wind conditions up to 11 mph, no full-shift CO exposures exceeded the evaluation criterion. Full-shift time-weighted average (TWA) exposures to the following occupational carcinogens were found: (1) benzene ranged from 0.03 to 0.1 ppm, with a mean of 0.05 ppm, (2) formaldehyde ranged from 0.013 to 0.029 ppm, with a mean of 0.018 ppm, (3) acetaldehyde ranged from 0.008 to 0.015 ppm, with a mean of 0.01 ppm, and (4) low levels of eight PNAs were detected including five that are known to have carcinogenic potential. All of the interviewed foresters reported having some recurring musculoskeletal problems associated with working with chainsaws. These primarily consisted of soreness in the fingers, wrists, elbows, and back. According to the most protective evaluation criteria, there was overexposure to CO among foresters at TNWR. Also, exposures to benzene, formaldehyde, acetaldehyde, and PNAs were detected. NIOSH recommends that exposure to occupational carcinogens be reduced as low as possible. Recommendations were provided to reduce exposure to chainsaw emissions by reducing the amount of chainsaw work per shift and to keep chainsaws as sharp as possible to reduce the duration of peak exposure when cutting larger trees.