Monitoring of firefighters exposure to smoke during fire experiments and wildfires

There is a general agreement about the importance of forest fires as a major emission source of air pollutants to the atmosphere. However, the current state of knowledge about the potential health impacts on the affected communities and, in particular, in the personnel involved in firefighting operations is still scarce. The most extensive measurements of smoke exposure among wildland firefighters were conducted in the United States of America (USA) and Australia. From these field studies it was possible to conclude that firefighters can be exposed to significant levels of carbon monoxide (CO) and respiratory irritants, including formaldehyde, acrolein, and respirable particulate matter. As a result, adverse health effects occur with acute, instantaneous eye and respiratory irritation and shortness of breath, developing into headaches, dizziness and nausea enduring up for several hours. Longer-term health effects, lasting days to months, have also been identified among wildland firefighters.

Particularly in Europe, where an average annual value of 500,000 hectares of forest was consumed by fire in the last 25 years, there is a significant lack of data on personal smoke exposure, which would allow to establish cause/effect relations between the air pollutants contained in smoke and firefighters health effects.

This paper describes the work developed under the research project FUMEXP, which aims to evaluate the effects of forest fire emissions on firefighters health for typical south European conditions. FUMEXP activities involved an extensive number of measurements of individual exposure to smoke pollutants and medical parameters for a group of firefighters along wildfires and experimental field burnings.

For the smoke exposure monitoring, 10 firefighters were selected from four different fire brigades, while for the medical tests the sample was composed by 38 firefighters. Firefighters were chosen based on predefined criteria that takes into account the age, gender, smoking habits, function in the fire brigade, etc... Individual exposure to CO, volatile organic compounds (VOC), nitrogen dioxide (NO2), methane (CH4) and particulate matter (PM2.5) was monitored with portable devices. Moreover, the location of each firefighter in time was registered with GPS equipment.

Aiming to analyse the potential respiratory effects of smoke, the selected firefighters were also medically evaluated before and after the exposure through different respiratory tests: ventilation function tests, determination of oxygen saturation, and monitoring of exhaled CO. In addition to these clinical tests, nitric oxide (NO) in the exhaled air and breath condensate have been determined respectively by the single breath method and using a non-invasive technique, which implies the analysis of a frozen air sample. Both methods allow the identification of respiratory lesion or inflammation and the measurement of important markers. These tests have been complemented by respiratory questionnaires.

As previously mentioned, the measurement of firefighters exposure to air pollutants was conducted during field burning experiments and real firefighting situations. The former were carried out in the central region of Portugal at the end of May 2008. Before the experiments the burning plots were prepared and the vegetation characteristics analysed. Along the burning experiments, and besides individual exposure of firefighters, also air quality and meteorological parameters were acquired.

While the fire experiments constitute a valuable opportunity for obtaining detailed data on several important parameters for the assessment of the smoke effects on human health, wildfires could provide data about the real importance and magnitude of the exposure of firefighters to smoke during daily activities. Therefore, along the 2008 summer, the selected firefighters carried on all the monitoring equipment in all their wild-land forest fire combat situations.

For all the monitored firefighters, a considerable number of the air pollutants concentration values acquired during their activity, both in the wildfires and in the fire experiments, is beyond the limits recommended by the World Health Organization (WHO), namely for PM2.5, CO, NO2 and VOC. Daily averages of PM2.5 concentration values as high as 470 µg.m-3 were obtained, well above the recommended limit of 25 µg.m-3. In terms of CO, hourly averaged values higher than 73,000 µg.m-3 were monitored, clearly above the 30,000 µg.m-3 recommended by the WHO. The highest NO2 hourly averaged measured value was 4,670 µg.m-3, once again much higher than the recommended value of 200 µg.m-3. For VOC, a maximum hourly average of 5,300 µg.m-3 was registered for one of the firefighters; however, due to the lack of recommended or legislated values it is not possible to establish a comparison.

The medical tests conducted on the firefighters, before and after the exposure to smoke, also indicate a considerable effect on the measured medical parameters, in particular an expressive increase of the CO concentration and a decrease of NO in the exhaled air of the majority of the firefighters.