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Health Hazards of Smoke Winter/Spring 1992


This section includes research abstracts and notes related to the health hazards of forest fire smoke.

Occupational Exposures in California Wildland Fire Fighting. B. Materna et al., American Industrial Hygiene Assoc. Journal, 53:69, 1992.

Industrial hygiene measurement of exposure to wildland firefighters was conducted in northern California during three consecutive fire seasons (1986-1989) in conjunction with three separate health effects studies. Chemicals that were monitored included carbon monoxide, total and respirable particulates, polyaromatic hydrocarbons (PAHs), crystalline silica, aldehydes, and benzene. Measurements were taken at both wildland fires and prescribed (planned) burns. A variety of collection methods were employed - colorimetric detector tubes and a CO monitor were used for direct-reading area measurements; colorimetric diffusion tubes, filter cassettes, sorbent tubes, and passive vapor monitors were used for determining personal time-weighted average exposures. A new screening method (NIOSH Method 2539) was used to identify the presence of specific aldehydes. Results show that wildland firefighters may at times be exposed to concentrations of carbon monoxide, total or respirable particulates, or silica at levels near or higher than recommended occupational exposure limits, although group means were generally well below the limits.

Time-weighted average formaldehyde levels, measured in a few instances above 0.37 mg/m³ (0.3 ppm), indicate a potential for formaldehyde-induced eye or respiratory irritation under these conditions. Certain characteristics of the work such as high altitude, temperature, and breathing rate; extended work shifts; and additional off-shift exposures suggest that adjustment of 8-hour exposure limits may be necessary to provide adequate protection. In part, because of the rigors of performing industrial hygiene measurements under firefighting conditions, data are limited and could not be considered representative of the full range of exposures firefighters may encounter. Further exposure monitoring is needed, particularly to identify job tasks and fire conditions that contribute to higher exposures. Short-term measurements should be done for acute hazards such as carbon monoxide and aldehydes. Recommendations are made for exposure reduction, medical surveillance, training, and additional research.

The Use Of Respiratory Protective Devices By Wildland Firefighters. J. Driessen, B. Sharkey, and D. Buskirk, Missoula Technology and Development Center, 1992.

Based on field interviews, a questionnaire was constructed to assess field use of respiratory protective devices by wildland firefighters during wildfire suppression or prescribed burning. Questionnaires were sent to field units of federal and state agencies for distribution and, therefore, represent a non-probability sample. Of the 300 respondents to the questionnaire, 53.8 percent were Forest Service' employees and 46.2 percent were employees of other federal or state agencies. A wide range of job titles was represented—47 forestry techs, 30 hotshots, and 17 fire management officers were the most common. Ages ranged form 18 to 56 years with a mean of 33.6 years; 94.6 percent of the respondents were male. Firefighting experience range from 1 to 36 years, with a mean of 11.1 years.

When asked, "Do you feel the health hazards of smoke in wildland firefighting and/or prescribed burning warrant the use of respiratory protective devices 82.2 percent responded yes. Of the 50.6 percent of respondents who had used respiratory protection, the overwhelming majority (92.9%) responded yes, protection was warranted. Seventy-two percent of those who had not used a device felt protection was warranted. Respondents felt protection was needed during direct attack (70.4%), line holding (79.8%), and mop-up (64.8%). Of those who had used a device, 37.5 percent used a disposable, 43.8 percent a half-face, and 18.8 percent a full-face respirator (18.8% marked other, and wrote in bandanna). Of those who had used a device, 76.1 percent said the device provided relief, but 75 percent reported that the device adversely affected productivity. In addition, 84.6 percent reported satisfaction with the fit of the device; only 7.1 percent reported problems with a beard, 12.6 percent with glasses, and 5.5 percent with hard hat and goggles. Also, 69.1 percent said the device interfered with communication (talking, radio), while 48.6 percent said a device that provides protection from some but not all hazards could provide a false sense of security. Most added that training would minimize that problem. The results indicate that firefighters believe that the health hazards of smoke warrant the use of respiratory protection, that the perceived need for protection increases with respirator use, and that fit and other problems are minor and manageable with proper training. (See summary of responses in Firefighters Respond).

Acrolein Effects Reviewedin Toxicological Profile for Acrolein, by U.S. Dept. of Health and Human Services, from National Technical Information Services, 1990.

In addition to throat irritation and a reflex suppression of respiratory rate, acrolein can cause destruction of the respiratory epithelium and its inherent defense mechanisms. Subjects experienced eye irritation after exposure to 0.6 ppm acrolein for 7.5 min, or to 0.17 ppm for 1 hour. Lacrimation (tears) occurred within 20 seconds in individual exposed to 0.81 ppm, and within 5 seconds at 1.22 ppm. A summary of human data shows that concentrations between 0.5 and 5 ppm caused lacrimation and various degrees of eye irritation in exposure periods of 10 minutes or less.

Exposure limits for acrolein are 0.1 ppm (OSHA, NIOSH, and ACGIH), with a short-term exposure limit (STEL) of 0.3 ppm (ACGIH or American Council of Government Industrial Hygienists). [Note: Exposure limits for acrolein have been exceeded in a small proportion of the exposure samples taken on wildland firefighters. Due to the sensitivity of the eyes to acrolein, eye irritation may provide warning of excess exposure to forest fire smoke.]

Effects Of Inhaled Particulate Matter. O. Raabe and D. Wilson, University of California, Davis, 1990.

Controlled laboratory studies were conducted using two experimental animal models, one healthy and one impaired with emphysematous lung disease, to evaluate the nature and severity of responses to inhaled respirable aerosols that were typical of air pollution in California, alone and in combination with ozone. Studies were performed with a respirable aerosol (similar to London smog), alone and in combination with sulfur dioxide. Exposures were acute (3 days) or subchronic (30 days). Effects were evaluated with biochemical measures, lung clearance, clinical signs, and histological evidence.

Neither aerosol was effective by itself in causing significant responses in healthy rats, but some significant aerosol effects were observed in association with ozone exposure or lung impairment. In the 3-day studies there were some significant increases in total lung DNA and protein content in rats exposed to the California aerosol compared to controls. In addition. small airway inflammation was observed in animals exposed to ozone, and this effect was exacerbated by inhalation of aerosol or in impaired animals. In 30-day studies, analyses showed increases in lung collagen and potential lung fibrosis in rats exposed to the California smog, and to the London aerosol in impaired animals. Both aerosols decreased the clearance rate with test particles. Airway lesions and fibrosis were associated with ozone exposure and were exacerbated by exposure to the California smog.

The Normal Range Of Diurnal Changes In Peak Expiratory Flow Rates: Relationship To Symptoms And Respiratory Distress. J. Quackenboss, M. Lebowitz and M. Krzyzanowski. American Review of Respiratory Disease, 143:323, 1991.

Measuring peak expiratory flow rates (PEFR) several times a day can provide an objective assessment of functional changes relative to environmental or occupational exposures. This report describes the pattern of diurnal changes in PEFR in a reference population, and defines ranges of normal between and within-day variability. An index of diurnal changes was defined as the ratio between maximal and minimal values where the maximal value was restricted to PEFR measured at noon or in the evening (N,E) and the minimal value was restricted to the morning or at bedtime (M,B). A ratio greater than normal represented an exaggeration of the normal diurnal pattern in PEFR. Normal limits, based on the ninety-fifth percentile in the reference population, were larger for children (130%,) than for adults 15 to 35 years of age (117%) and those older than 35 years of age (118%). The meaningfulness of excessive diurnal changes in PEFR was examined by relating this ratio (max/min) to chronic respiratory symptoms and diseases in 9391 adults and children who recorded PEFR values 2 to 4 times per day for as long as 14 days. There was a strong relationship of diurnal changes in PEFR that exceed normal limits with physician-confirmed asthma (relative risk of 2.99 with max/min) with exertional dyspnea (Grade 2+), and with more frequent reporting of acute symptoms of wheeze, attacks of wheezing dyspnea, cough and chest colds. In addition, those exceeding the normal limits had about 2.9 times greater risk of having FEV 1 below 80 percent of predicted, and nearly 7 times greater risk of being below 70 percent. These associations support the interpretation of excessive diurnal changes in PEFR as an indicator of bronchial responsiveness. [Note: The PEFR were at least as sensitive as provocative methacholine challenge tests in determining bronchial responsiveness. Along with other pulmonary function tests, the PEFR measures could help identify those likely to experience respiratory problems when exposed to forest fire smoke.]

Respiratory Symptoms And Risk Factors In An Arizona Population Sample Of Anglo And Mexican-American Whites. C. Di Pede, et al., Chest, 99:916, 1991.

Prevalence rates of respiratory symptoms and diseases in a large group of Anglos and Mexican-Americans were analyzed. Each subject completed a questionnaire. Among current smokers, chronic productive cough and dyspnea were significantly higher in both ethnic groups; wheezy symptoms were higher in Anglos. There were no significant differences in the symptom prevalence rates between the two groups, after stratifying by current cigarette consumption and childhood respiratory trouble (CRT). The spirometric values were not significantly different. In both ethnic groups, the prevalence rates of wheeze, shortness of breath with wheeze (SOBWHZ) and asthma were significantly higher in those who had CRT. Among Anglos, less educated smokers had significantly higher prevalence rates of SOBWHZ, and dyspnea; nonsmokers with less education had higher prevalence rates of cough, chronic cough, and dyspnea. Our results confirm the importance of CRT and lower educational level as risk factors for respiratory symptoms. Ethnicity is not associated with symptomology or lung function impairment. [Note: Dyspnea is shortness of breath, difficult or labored respiration.]

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