A NIOSH evaluation of health hazards encountered by firefighters for a state-based wildland fire management program found overexposures to carbon monoxide, noise, wood dust, and vibration during “fuel reduction” activities such as thinning trees and removing underbrush. The evaluation involved confidential medical interviews conducted on two occasions in 2015 and a follow-up visit in 2016 during which NIOSH personnel evaluated work tasks and administered a questionnaire covering work history. Personal air sampling results for carbon monoxide were below full-shift occupational exposure limits, but NIOSH found brief, intermittent exposures that exceeded the agency’s ceiling limit of 200 ppm.  Six of nine air sampling results for wood dust, which NIOSH considers a potential carcinogen, were above the NIOSH recommended exposure limit and the ACGIH threshold limit value of 1.0 mg/m3.  For noise, exposures to five workers over two days of monitoring exceeded the NIOSH REL and the OSHA action level of 85 dBA over an eight-hour work shift.  NIOSH personnel measured vibration for two sawyers using four different chainsaw models. Seventy-three percent of firefighters who participated in the medical evaluations reported symptoms that could be consistent with hand-arm vibration syndrome, or HAVS. NIOSH's recommendations about how to address these hazards are available in the full report (PDF).