Wildland firefighter smoke exposure and risk of lung cancer and cardiovascular disease mortality.

Wildland firefighters are exposed to wood smoke, which contains hazardous air pollutants, by suppressing thousands of wildfires across the U. S. each year. We estimated the relative risk of lung cancer and cardiovascular disease mortality from existing PM2.5 exposure-response relationships using measured PM4 concentrations from smoke and breathing rates from wildland firefighter field studies across different exposure scenarios. To estimate the relative risk of lung cancer (LC) and cardiovascular disease (CVD) mortality from exposure to PM2.5 from smoke, we used an existing exposure-response (ER) relationship. We estimated the daily dose of wildfire smoke PM2.5 from measured concentrations of PM4, estimated wildland firefighter breathing rates, daily shift duration (hours per day) and frequency of exposure (fire days per year and career duration). Firefighters who worked 49 days per year were exposed to a daily dose of PM4 that ranged from 0.15 mg to 0.74 mg for a 5- and 25-year career, respectively. The daily dose for firefighters working 98 days per year of PM4 ranged from 0.30 mg to 1.49 mg. Across all exposure scenarios (49 and 98 fire days per year) and career durations (5-25 years), we estimated that wildland firefighters were at an increased risk of LC (8 percent to 43 percent) and CVD (16 percent to 30 percent) mortality. This unique approach assessed long term health risks for wildland firefighters and demonstrated that wildland firefighters have an increased risk of lung cancer and cardiovascular disease mortality.

Factors affecting smoke and crystalline silica exposure among wildland firefighters.

Smoke exposure data among U.S. wildland firefighters for carbon monoxide, respirable particulate and respirable crystalline silica are presented from a field surveillance program between 2009 and 2012. Models to predict fireline-average exposure to each inhalation hazard were developed and fit to the available data. The models identify factors to consider when defining similar exposure groups and designing future data collection. Task-based rather than shift-average data collection is important because the work activity representing the majority of fireline time, the position up- or downwind of the fire, and the proportion of time this combination represented were significant factors in the model for carbon monoxide, and all but wind position were significant for respirable particulate matter. The wind position versus the fire was not important for respirable quartz exposure. The crew type was an important factor in each model.

Noise exposures and perceptions of hearing conservation programs among wildland firefighters.

Wildland firefighters are exposed to numerous noise sources that may be hazardous to their hearing. This study examined the noise exposure profiles for 264 wildland firefighters across 15 job categories. All 264 firefighters completed questionnaires to assess their use of hearing protection devices, enrollment in hearing conservation programs, and their overall perception of their noise exposure. Roughly 54% of firefighters' noise exposures exceeded the National Institute for Occupational Safety and Health recommended exposure limit of 85 decibels, A-weighted, over 8 hr, and 32% exceeded the Occupational Safety and Health Administration permissible exposure limit of 90 decibels, A-weighted, over 8 hr. Questionnaire results indicated good agreement between noise exposures and firefighters' perceptions of the noise hazard. Approximately 65% reported that they used some form of hearing protection; however, only 19% reported receiving any proper training regarding the use of hearing protection devices, with the majority of those firefighters relying on earplugs, including electronic and level-dependent earplugs, over earmuffs or other forms of hearing protectors. The results also suggest that improved communication and situational awareness play a greater role in the consistent use of hearing protection devices than other factors such as risk of developing noise-induced hearing loss. The study highlighted the challenges facing wildland firefighters and their management and the need for a comprehensive wildland fire agencies' hearing conservation program especially for firefighters who were exempt based on their occupational designations.

Carbon monoxide exposures among U.S. wildland firefighters by work, fire, and environmental characteristics and conditions.

Carbon monoxide (CO) exposure levels encountered by wildland firefighters (WLFs) throughout their work shift can change considerably within a few minutes due to the varied tasks that are performed and the changing environmental and fire conditions encountered throughout the day. In a U.S. Forest Service study during the 2009-2012 fire seasons, WLFs from 57 different fires across the U.S. were monitored for CO using CO data-logging detectors while an observer recorded worker tasks, fire characteristics, and environmental conditions at scheduled intervals. Exposures to CO for 735 WLF's work shifts were analyzed to assess the effect of variations among work tasks, fire characteristics, and environmental conditions. Geometric mean full shift time-weighted averages were low at 2.4 parts per million (ppm) and average length of work shift was 11 hr and 15 min. The task with the highest mean CO exposure was sawyer/swamper at 6.8 ppm; workers performing that task had an estimated 9 times higher odds of a having a 1-min CO measurement exceeding 25 ppm than the referent pump task (OR = 8.89, 95% CI = 1.97, 40.24). After adjusting CO exposure limits for shift length, elevation, and work level, 2% and 4% of the WLF's work shifts exceeded the National Institute for Occupational Safety and Health's recommended exposure level and the American Conference of Governmental Industrial Hygienist's threshold limit value, respectively. In regression modeling, variables that were significantly associated with elevated levels of CO exposure included: task, fuel model, wind orientation, crew type, relative humidity, type of attack, and wind speed. In the absence of instruments such as CO detectors that can determine and alert WLFs to elevated CO levels, recognition of the conditions that lead to elevated levels of CO exposure can assist WLFs to effectively use administrative controls, such as work rotations, to minimize exposures.

Noise exposure among federal wildland fire fighters.

Wildland fire fighters use many tools and equipment that produce noise levels that may be considered hazardous to hearing. This study evaluated 174 personal dosimetry measurements on 156 wildland fire fighters conducting various training and fire suppression tasks. Noise exposures often exceeded occupational exposure limits and suggest that wildland fire fighters may be at risk of developing noise-induced hearing loss, particularly those operating chainsaws, chippers, and masticators. The authors recommend a comprehensive approach to protecting these fire fighters that includes purchasing quieter equipment, noise and administrative controls, and enrolling these fire fighters into a hearing conservation program.

Review of the health effects of wildland fire smoke on wildland firefighters and the public.

Each year, the general public and wildland firefighters in the US are exposed to smoke from wildland fires. As part of an effort to characterize health risks of breathing this smoke, a review of the literature was conducted using five major databases, including PubMed and MEDLINE Web of Knowledge, to identify smoke components that present the highest hazard potential, the mechanisms of toxicity, review epidemiological studies for health effects and identify the current gap in knowledge on the health impacts of wildland fire smoke exposure. Respiratory events measured in time series studies as incidences of disease-caused mortality, hospital admissions, emergency room visits and symptoms in asthma and chronic obstructive pulmonary disease patients are the health effects that are most commonly associated with community level exposure to wildland fire smoke. A few recent studies have also determined associations between acute wildland fire smoke exposure and cardiovascular health end-points. These cardiopulmonary effects were mostly observed in association with ambient air concentrations of fine particulate matter (PM2.5). However, research on the health effects of this mixture is currently limited. The health effects of acute exposures beyond susceptible populations and the effects of chronic exposures experienced by the wildland firefighter are largely unknown. Longitudinal studies of wildland firefighters during and/or after the firefighting career could help elucidate some of the unknown health impacts of cumulative exposure to wildland fire smoke, establish occupational exposure limits and help determine the types of exposure controls that may be applicable to the occupation.