Wildfire Smoke Inhalation: Who is Most at Risk?
Wildfires can move through grassland at up to 14 mph. This means that in a very short time period they can cover a vast area. The smoke that the fires produce will move even further through the atmosphere. Anyone within the fire smoke boundary will have increased air pollution exposure. However, there are subpopulations that are at enhanced risk due to two factors; 1) increased exposure, and 2) increased susceptibility.
Dr Kelly BéruBé told us that fire fighters are at particular risk of inhalation of wildfire smoke particles. They will have high exposure due to 1) long working hours, 2) increased respiration due to physical activity and 3) often a lack of self-contained breathing apparatus.
Dr BéruBé says that in addition, “Certain population groups are at particular risk of respiratory effects from bushfire smoke, including young children, those with pre-existing cardiopulmonary conditions, and smokers.”
Health Effects of Wildlife Smoke
Health effects from exposure to wildfire smoke can be very wide-ranging, including eye irritation, respiratory symptoms, cardiovascular effects and mortality. Landscape fires (which include wild and planned forest fires, agricultural burning, peat burning and grass fires) have been found to cause 339,000 deaths annually. A team of researchers lead by Fay Johnston at the University of Tasmania investigated the mortality effects of Australian wildfires between 1994 and 2007, and found a 5% increase in non-accidental mortality on days classified as bushfire smoke event days.
Current WHO guidelines consider all particulate matter to be equally toxic, for example particles from wildfires are assumed to be of equal toxicity as traffic and mineral particles, but some researchers disagree. Dr BéruBé comments, “PM10 from wildfires appear to have different effects on health than urban PM10, whereby wildfire smoke causes increased hospital admissions for respiratory complaints and urban PM10 is associated with cardiovascular mortality.”
The exposure to wildfire smoke is very different than exposure to urban dust. People are exposed to consistent levels of urban dust in the home, work and outside (chronic exposure). In contrast, wildfire smoke means exposure to high levels of particles over shorter timescales (acute exposure). In areas where wildfires are prevalent, this exposure can be more chronic.
The problem with identifying the toxic effects of wood smoke is the same as with urban particles; they’re a mixture of different components, and the fraction responsible for toxicity is still uncertain.
Climate Change, Wildfires, and Air Pollution
Climate change predictions for the next century include periods of drier air, lower humidity and stronger winds; three factors which contribute to the likelihood, longevity and intensity of wildfires. In the UK for example, wildfires are predicted to increase due to climate change by 30 – 50% by 2080. The effect of climate change upon wildfire prevalence can be modulated, for example by not developing into areas prone to wildfires and through landscape management. Currently, it seems that little is being done to limit the problem. However, if the media interest in wildfires continues as the fires rage on, it seems they will have no choice but to do more.
ABC7. Colorado wildfires: Updates on West Fork Fire, Papoose Fire, East Peak Fire, Wild Rose Fire, more. (2013). Accessed July 4, 2013.
Gabbert, B. Fires in Sumatra Smoke Out Singapore. (2013). Wildfire Today. Accessed July 4, 2013.
Johnston, F.H., Henderson, S.B., Chen, Y., Randerson, J.T., Marlier, M., DeFries, R.S., Kinney, P., Bowman, D. M.J.S., Brauer, M. (2012). Estimated Global Mortality Attributable to Smoke from Landscape Fires. Environmental Health Perspectives. 120, 5: 695-701. DOI: 10.1289/ehp.1104422. Accessed July 4, 2013.
Moffat, A.J., Morison, J.I.L., Nicoll, B., Bain, V. Climate Change Risk Assessment for the Forestry Sector. (2012). Accessed July 4, 2013.
Caamano-Isorna, F., Figueiras, A., Sastre, I., Montes-Martínez, A., Taracido, M., Piñeiro-Lamas, M. Respiratory and mental health effects of wildfires: an ecological study in Galician municipalities (north-west Spain). (2011). Environmental Health. 10, 48: 1-9. DOI: 10.1186/1476-069X-10-48. Accessed July 4, 2013.
Johnston, F., Hanigan, I., Henderson, S., Morgan, G., Bowman, D. Extreme air pollution events from bushfires and dust storms and their association with mortality in Sydney, Australia 1994–2007. (2011). Environmental Research, 111, 6: 811-816. DOI: 10.1016/j.envres.2011.05.007. Accessed July 4, 2013.
Naeher, L.P., Brauer, M., Lipsett, M., Zelikoff, J.T., Simpson, C.D., Koenig, J.Q., Smith, K.R. Woodsmoke Health Effects: A Review. (2007). Inhalation Toxicology, 19:67-106. DOI: 10.1080/08958370600985875. Accessed July 4, 2013.
Orange County Fire Authority (OCFA). Are you prepared for a wildfire? Accessed July 4, 2013.
Westerling, A.L., Hidalgo, H.G., Cayan, D.R., Swetnam, T.W. Warming and Earlier Spring Increases Western U.S. Forest Wildfire Activity. (2006). Sciencexpress. Accessed July 4, 2013.