Dose Exposures to Air Pollutants Among Firefighters

There have been more studies documenting adverse health effects for wildland firefighters than there have been studies of firefighters at prescribed burns.

In general, fire workers experience acute, subchronic, and chronic effects of exposure to forest fires. The acute exposures to respirable irritants that fire workers sometimes experience can result in runny noses, tearing eyes, stinging eyes and nose, and declines in lung function (Reinhart, Ottmar, and Hanneman 2000). A study of Time Weighted Average showed that the exposure of wildland firefighters to particulate matter exceeds the Occupational Safety and Health Administration-Permissable Exposure Limit (OSHA-PEL) (Materna and others 1999). A study of a mop-up crew at a forest fire, found that 14% of exposures to total particulate matter exceeded the OSHA ceiling limit. Exposures to polynuclear aromatic hydrocarbons (PAHs) and crystalline silica among this crew were below OSHA-PELs. In some cases, the exposure of firefighters to PAHs may be consistent and long term, extending for several weeks while they are on duty (Rothman and others 1993). Chronic lung dysfunction among fire workers can occur as a result of the cumulative effects of exposures to smoke over longer time spans (Liu and others 1992).

Exposure to unsafe levels of carbon monoxide from burning vegetation can cause fire workers to have nausea, headaches, fatigue, can impair cognitive abilities, and can reduce their work capacity (Reinhart, Ottmar, and Hanneman 2000). Research on fire worker exposures to carbon monoxide is ambiguous on the issue of dose-exposures. In some cases, firefighters may receive doses of particulate matter that are greater than limits established by federal regulatory agencies (Liu and others 1992). Some studies found that fire workers’ exposures to carbon monoxide during an 8-hour work shift did not exceed the OSHA-PEL (McMahon and Bush 1992).

At wildland fires, instantaneous carbon monoxide exposures of fireline crew were below the OSHA ceiling limit in one study. Other studies suggest that fire workers may be exposed to dangerous levels of carbon monoxide. A study of fire workers downwind from a North Carolina fire showed that they were exposed to levels of carbon monoxide that were much higher that OSHA ceiling limits (Brauer 1999). Another study of wildland firefighers documented that they are at risk for being exposed to carbon monoxide concentrations well above the National Institute of Occupational Safety and Health (NIOSH) recommended limit (Materna and others 1992). At the 1988 Yellowstone Fires, firefighters suffered declines in lung function and increases in methcholine responsiveness (Materna and others 1992). Dust is the only air pollutant for which exposures among Yellowstone firefighters exceeded NIOSH occupational limits. The carbon monoxide exposures among gasoline pump operators at forest fires can be extremely high, exceeding the OSHA ceiling limit (Materna and others 1992).

In another study, researchers measured 200 shift-exposures and burn-duration Time Weighted Average (TWA) exposures to pollutants among prescribed fire crews over a period of 3 years (Reinhart, Ottmar, and Hanneman 2000). The exposure measurements were taken for a variety of fire workers including the burn boss, lighting crew, holding crew, holding supervisor, attack crew, engine drivers and riders, sawyer, and mop-up crew. Two percent of the group exceeded the American Council of Governmental and Industrial Hygienists-Threshold Limit Value (ACGIH-TLV) for carbon monoxide during an 8-hour work shift. Eight percent exceeded carbon monoxide limits during a total burn (Reinhart, Ottmar, and Hanneman 2000). For respirable irritants (formaldehyde, acrolein, and particulate matter [PM_3.5]), 14% of shift-average exposures and 30% of exposures for the total burn exceeded ACGIH-TLVs.

Fire workers may be exposed to aldehydes at levels that exceed OSHA-PELs (Liu and others 1992). Aldehydes that have been detected in biomass smoke include formaldehyde, acetaldehyde, furfural, and acrolein. One study found that biomass smoke contains more formaldehyde than any other aldehyde while another study found acrolein to be the most abundant of the aldehydes (Materna and others 1992).

In their research, Spear and Cannell (2002) found that, among mixmasters whom they surveyed, exposures to respirable dust, dyes, and hydrogen cyanide in retardants never exceeded the limits dictated by ACGIH TLV-TWAs or OSHA PEL-TWAs. Mixmasters are the group of fire workers who prepare the retardants that are used to control forest fires. Common fire suppressants such as Fire-Trol GTS R and Fire-Trol 300F contain potentially hazardous chemicals. Typically, retardants are prepared by mixing water into powdered chemicals. These chemicals are effective fire suppressants, but are also potentially toxic to humans. Exposure to the ammonium sulfate in these retardants may cause “hypermotility, diarrhea, nausea, and vomiting from ingestion” (Spear and Cannell 2002: 66). The diammonium phosphate in retardants may cause dermatitis, emphysema, asthma attacks, and irritations of the eyes, respiratory tract, and gastrointestinal tract. Long-term exposure to retardants may cause irritations to the eyes, skins, and respiratory tract.