Health Hazards of Smoke Spring 2001
Fire Storm 2000 (continued)
Fine Particles—Recent research concerning the adverse health effects of fine particles has led to a proposal for a new EPA standard for PM2.5 particulate. The fine particles can be inhaled deep into the lungs where they cause irritation and breathing problems. Larger particles are swept upward by ciliary action and expectorated. Fine particles have the potential to carry carcinogens deep into the respiratory system.
Fine particles constitute a high percentage of total particulate from wood smoke. Long-term exposure to fine particles has been associated with respiratory and cardiovascular illness and death. The PM2.5 standard is 15 µg/m3 for an annual daily average and 65 µg/m3 for a 24-hour average. Missoula experienced a high of 179 µg/m3 on the 10th of August. Data collected by MTDC in Hamilton, MT, indicate that PM2.5 concentrations were greater than 100 µg/m3 six times from August 15 to August 29. During at least 2 days, concentrations averaged between 200 and 300 µg/m3 (figure 2).
Figure 2—Twenty-four hour average PM2.5 concentration
at Hamilton and Missoula, MT, during August 2000.
From: MTDC Watershed, Soil and Air program.
The MTDC Watershed, Soil, and Air program conducted a collocation study of real-time particulate monitors in the Missoula and Bitterroot Valleys during Fire Storm 2000. The real-time particulate instruments use particle light-scattering (nephelometers) and light-absorption (aethalometers) principles to estimate particulate concentrations in real time. Results from the five different real-time instruments were compared to gravimetric results from a collocated Federal Reference Method PM2.5 sampler.
Results indicate that the real-time instruments tend to overestimate particulate concentrations, sometimes by more than twice the actual concentration. However, the overestimated results were linear over the entire range of particulate concentrations (from less than 10 µg/m3 to more than 400 µg/m3 as calculated by the Federal Reference Method sampler), so correction curves or equations could be established for each instrument. Results presented here represent corrected values.
Other Hazards—The smoke from forest fires contains other hazards, including carbon monoxide, formaldehyde, acrolein, and benzene. Carbon monoxide levels higher than 40 parts per million (ppm) have been recorded during heavy smoke exposures. The EPA 24-hour standard for carbon monoxide is 9 ppm, while the Occupational Safety and Health Administration (OSHA) 8-hour permissible exposure limit is 50 ppm. High levels of carbon monoxide can cause headaches, irritability, and nausea, and they are a risk for individuals with established heart disease. Formaldehyde and acrolein cause the eye and respiratory irritation experienced during exposure to smoke. Formaldehyde is a potential carcinogen, but only at levels far above those encountered by wildland firefighters. Benzene becomes a risk for firefighters who regularly work around fuel and engines. Because the concentrations of the different hazards in smoke are correlated, a high level of carbon monoxide suggests elevated levels of particulate and aldehydes.
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