Lung function measures following simulated wildland firefighter exposures

Abstract

Across the world, biomass smoke is a major source of air pollution and is linked with a variety of adverse health effects. This is particularly true in the western US where wood smoke from wildland forest fires are a significant source of PM2.5. Wildland firefighters are impacted as they experience elevated PM2.5 concentrations over extended periods of time, often occurring during physical exertion. Various epidemiological studies have investigated wood smoke impacts on human health, including occupational field exposures experienced by wildland firefighters. As there are numerous challenges in carrying out these field studies, having the ability to research the potential health impacts to this occupational cohort in a controlled setting would provide important information that could be translated to the field setting. To this end, we have carried out a simulated wildland firefighter exposure study in a wood smoke inhalation facility. Utilizing a randomized crossover trial design, we exposed 10 participants once to clean filtered-air, 250 μg/m3, and 500 μg/m3 wood stove-generated wood smoke PM2.5. Participants exercised on a treadmill at an absolute intensity designed to simulate wildland firefighting for 1.5 hours. In addition to measured PM2.5 smoke concentrations, mean levels of CO2, CO, and % relative humidity were continuously monitored and recorded and were representative of occupational ‘real-world’ exposures. Pulmonary function was measured at three time points: before, immediately after, and 1-hour post-exposure. Although there were some reductions in FVC, FEV1, and FVC:FEV1 measures, results of the spirometry testing did not show significant changes in lung function. The development of this wood smoke inhalational facility provides a platform to further address unique research questions related to wood smoke exposures and associated adverse health effects.

Controlled human exposures to wood smoke: a synthesis of the evidence

“…The findings from these 12 studies (across 22 publications) may be better understood by synthesizing the results by endpoint, as summarized in Tables 2 , 3 , 4 , 5 , where effects on lung inflammation, circulating cells and proteins, oxidative stress, and cardiovascular physiology are presented, respectively. Lung function (not summarized in table) was investigated by spirometry in 5 studies [ 16 , 20 , 23 , 31 , 35 ] but no significant changes in principal spirometry values (FEV 1 , FVC, or FEV 1 /FVC) were observed in any of the studies, even though different concentrations and properties of WS were applied.…”

“…Ferguson et al [23] reported effects on lung function from the same human controlled exposure study. Although a slight decrease in forced expiratory volume in 1 s (FEV 1 ), forced vital capacity (FVC), and the ratio of these values (FEV 1 /FVC) was observed, none of these results reached significance.…”

“…Similarly, air-starved operation of a pellet stove [20] will also result in emissions dominated by organics, although soot and ash particles are also emitted. With increasing temperatures and air supply, soot aggregates will be formed, resulting in emission of a mixture of soot and organics from flaming combustion in stoves, fireplaces and open fires [21][22][23][24][25][26][27][28][29][30]. Upon even more complete combustion conditions (eg, highest temperatures in stoves with good air supply) soot is reduced to inorganic ash, consisting of elements that are refractory to combustion [31][32][33]38].…”

Experimental Woodsmoke Exposure During Exercise and Blood Oxidative Stress

“…Finally, given the current findings of oxidative stress, next generation investigations should also explore associations to physiologic outcomes. Our research group recently published a parallel investigation from this subject cohort and found no changes in respiratory function (42), though there is reason to suspect that aforementioned smoke and exercise doses might alter pulmonary responses (43). Thus, linking oxidative stress responses to potential changes in vascular, cardiac and respiratory parameters may provide new insights into clinical outcomes.…”

A comparative analysis of biomass and clean fuel exposure on pulmonary function during cooking among rural women in Tamilnadu, India

“…Similarly, in our study, there was a significant decline in FEF25-75%, which indicates early small airway obstruction. A study reports showed a significant decline in PEFR with increasing duration of exposure due to chronic exposure to biomass fumes in poor ventilation of indoor kitchen which causes inflammation of airways among women [ 16 ]. Similarly, we also observed in our study a significant decline in PEFR among rural women who were prolonged exposure to biomass smoke, which indicates large airway obstruction.…”