Fire fighters' exposure to carbon monoxide during Australian bushfires

Fatal entrapments of Australian bushfire fighters have led to suggestions that carbon monoxide (CO) poisoning could have contributed to these accidents by impairing the fire fighters' judgement. Carboxyhemoglobin saturation (COHb%) levels were assessed from alveolar CO levels in 24 fire fighters working with handtools and in 12 accompanying scientific observers, before and after fire fighting (duration 37-187 min) on 15 experimental bushfires. Carboxyhemoglobin levels increased on average by 0.7% per hour in the fire fighters and by 0.3% per hour in the observers. Nonsmoking fire fighters had lower COHb% after fires than the smokers had before fires. Estimates of environmental CO concentrations (including cigarette smoke) during the fires averaged 31 parts per million (ppm) for the smokers, 17 ppm for the nonsmoking crew members, and 11 ppm for the observers, none of whom smoked. The highest estimates of environmental CO arising solely from bushfire smoke were 40 to 50 ppm. Smokers were exposed to as much CO from their cigarettes as from bushfire smoke. Carboxyhemoglobin levels at the end of 8-hr fire fighting shifts, predicted from these levels of environmental CO, averaged about 5% (maximum 11%) in smokers and about 3% (maximum 7%) in nonsmokers. Acute levels of COHb% of this degree are not considered to have significant effects on health or performance. These results indicate that bushfire fighters are generally unlikely to experience hazardous levels of CO exposure.     

Occupational exposures in California wildland fire fighting.

Industrial hygiene measurement of exposures to wildland fire fighters 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 (National Institute for Occupational Safety and Health Method 2539) was used to identify the presence of specific aldehydes. Results show that wildland fire fighters 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-hr exposure limits may be necessary to provide adequate protection. In part, because of the rigors of performing industrial hygiene measurements under fire fighting conditions, data are limited and could not be considered representative of the full range of exposures fire fighters may encounter.(ABSTRACT TRUNCATED AT 250 WORDS)     

Baseline measurements of smoke exposure among wildland firefighters

Extensive measurements of smoke exposure among wildland firefighters are summarized, showing that firefighters can be exposed to significant levels of carbon monoxide and respiratory irritants, including formaldehyde, acrolein, and respirable particulate matter. Benzene was also measured and found to be well below permissible exposure limits, with the highest concentrations occurring among firefighters working with engines and torches burning petroleum-based fuel. Exposures to all pollutants were higher among firefighters at prescribed burns than at wildfires, while shift-average smoke exposures were lowest among firefighters who performed initial attack of wildfires in the early stages of the fires. Smoke exposure reaches its highest levels among firefighters maintaining fire within designated firelines and performing direct attack of spot fires that cross firelines. These events and the associated smoke exposures were positively correlated with increasing ambient wind speeds, which hamper fire management and carry the convective plume of the fire into firefighters' breathing zone. The pollutants measured in smoke were reasonably well-correlated with each other, enabling estimation of exposure to multiple pollutants in smoke from measurements of a single pollutant such as carbon monoxide.     

Carbon monoxide levels in the breath of smokers and nonsmokers: effect of domestic heating systems.

Breath and ambient (room) carbon monoxide (CO) levels were measured in a random sample of 168 adults in their own homes. The levels of breath CO in the 69 smokers ranged from 3 ppm to over 100 ppm, 74% being above 10 ppm; mean levels in the 99 nonsmokers were lower than in the smokers, 79% being below 6 ppm. In the remaining 21% of nonsmokers with higher breath levels than expected, the ambient CO was also found to be elevated, ranging up to 38 ppm. A close correlation in the nonsmokers was found between the breath and ambient CO levels (r = 0.952, p less than 0.001). The rooms with the elevated ambient CO levels (above 5 ppm) were those which, at the time of testing, were being heated by gas radiant heaters, open fires or stoves. The maximum ambient CO in the rooms of smokers with non CO generating heating was 16 ppm. The results suggest that many people, both smokers and nonsmokers, may be at risk from CO generated by certain domestic heating systems and that nonsmokers are far more likely to be exposed to high levels of CO from these sources than from being in a room with a heavy smoker. Poor ventilation associated with the current trend towards excluding all draughts is likely to exacerbate the situation for both smokers and nonsmokers.     

Air Pollution in Road Tunnels

As a part of a study of pollution of the air by motor vehicles, measurements have been made in two London road tunnels during periods of high traffic density. The concentrations of smoke and polycyclic hydrocarbons found there are much higher than the average values in Central London, but they are of the same order of magnitude as those occurring during temperature inversions on winter evenings when smoke from coal fires accumulates at a low level.

An attempt has been made to relate the concentration of each pollutant to the type and amount of traffic. Both diesel and petrol vehicles make some contribution to the amounts of smoke and polycyclic hydrocarbons found in the tunnels, but in the case of smoke, fluoranthene, 1: 2-benzpyrene, pyrene, and 3: 4-benzpyrene, the concentrations appear to be more closely related to the density of diesel traffic than to that of petrol traffic. The concentrations of lead and carbon monoxide have also been determined, and these are very closely related to the density of petrol traffic. During the morning and evening rush hours the mean concentration of carbon monoxide was just over 100 p.p.m. and peak values up to 500 p.p.m. were recorded at times. Oxides of nitrogen were determined in some of the experiments and there was always much more nitric oxide than nitrogen dioxide. Eye irritation was experienced but its cause was not investigated.

The concentration of pollution in the tunnels does not appear to be high enough to create any special hazards for short-term exposures. The amosphere at peak periods may become very dirty and unpleasant and the concentration of carbon monoxide would be sufficient to produce some effect over a period of several hours' continuous exposure. The total emission of pollution from road vehicles must still be small in comparison with that from coal fires, but the effect of traffic on the concentration of smoke, polycyclic hydrocarbons, carbon monoxide, and lead in the air of city streets deserves continued study.

     

A study of serum thiocyanate concentrations in office workers as a means of validating smoking histories and assessing passive exposure to cigarette smoke

Patients in clinical practice often falsely report their smoking status. To see if this was so in occupational surveys we have validated smoking histories (using a serum thiocyanate assay) in 206 randomly sampled office workers who completed a smoking questionnaire administered by a doctor. Past and present cigarette consumption was determined with an assessment of exposure to passive cigarette smoke at home and at work in the non-smokers. Serum thiocyanate concentrations were measured by the ferric nitrate method. All smoking groups showed mean thiocyanate concentrations greater than non-smokers except those smoking five or fewer cigarettes a day. There was a significant increase in plasma thiocyanate with increasing smoking (p less than 0.01). Non-smokers with and without exposure to passive smoke could not be separated by thiocyanate concentration. In our hands serum thiocyanate concentrations identified moderate and heavy smokers but could not distinguish between non-smokers, light smokers, and passive smokers. Fourteen non-smokers had serum thiocyanate concentrations higher than 70 mumol/l which were still raised on a repeat sample. On a further questionnaire two admitted to smoking. To help confirm non-smoking status, expired carbon monoxide levels were also checked in this group. One person had a level of 22 ppm and subsequently admitted to smoking. In the others the levels were less than or equal to 10 ppm. Using a combination of serum thiocyanate assay and exhaled breath carbon monoxide levels, non-smoking was confirmed in 98% of those stating that they were non-smokers. In non-smokers exposure to passive cigarette smoke was much more likely to occur at work than at home.     

A study of serum thiocyanate concentrations in office workers as a means of validating smoking histories and assessing passive exposure to cigarette smoke.

Patients in clinical practice often falsely report their smoking status. To see if this was so in occupational surveys we have validated smoking histories (using a serum thiocyanate assay) in 206 randomly sampled office workers who completed a smoking questionnaire administered by a doctor. Past and present cigarette consumption was determined with an assessment of exposure to passive cigarette smoke at home and at work in the non-smokers. Serum thiocyanate concentrations were measured by the ferric nitrate method. All smoking groups showed mean thiocyanate concentrations greater than non-smokers except those smoking five or fewer cigarettes a day. There was a significant increase in plasma thiocyanate with increasing smoking (p less than 0.01). Non-smokers with and without exposure to passive smoke could not be separated by thiocyanate concentration. In our hands serum thiocyanate concentrations identified moderate and heavy smokers but could not distinguish between non-smokers, light smokers, and passive smokers. Fourteen non-smokers had serum thiocyanate concentrations higher than 70 mumol/l which were still raised on a repeat sample. On a further questionnaire two admitted to smoking. To help confirm non-smoking status, expired carbon monoxide levels were also checked in this group. One person had a level of 22 ppm and subsequently admitted to smoking. In the others the levels were less than or equal to 10 ppm. Using a combination of serum thiocyanate assay and exhaled breath carbon monoxide levels, non-smoking was confirmed in 98% of those stating that they were non-smokers. In non-smokers exposure to passive cigarette smoke was much more likely to occur at work than at home.     

EVALUATED COMMUNITY FIRE SAFETY INTERVENTIONS IN THE UNITED STATES: A REVIEW OF CURRENT LITERATURE

The purpose of the study was to assess the state of fire prevention research, provide an updated synthesis of evaluated fire prevention programs, and discuss the role of fire fighters and data systems in prevention efforts. The review included all evaluations of U.S. based fire prevention interventions published between January 1998 and September 2004 and any earlier articles about U.S. fire prevention interventions not included in two prior review articles. We retrieved information from each identified study including evaluation findings, involvement of fire service personnel and use of existing data systems. We identified twelve articles: seven reported on smoke alarm interventions, three on multi-faceted programs, and two other programs. Five programs involved fire service personnel in the design, implementation, and/or evaluation, and three used existing data systems. Studies reviewed suggest that canvassing and smoke alarm installations are the most effective means of distributing alarms and increasing the functional status of distributed alarms. The functionality of smoke alarms, an issue noted in earlier reviews, remains a problem. Programs involving partnerships with fire departments have indicated success in preventing fires and deaths, improving smoke alarm ownership and functional status, and improving children's fire safety knowledge. Using existing data systems to target and to evaluate interventions was effective. In the years since prior reviews, some improvements in the rigor of evaluation designs have been made, but there is still a need for high quality evaluations that will inform fire injury prevention efforts.     

Effects of carbon monoxide on behavior in monkeys in relation to human fire hazard

Although studies have been made of the behavioral effects of low levels of carbon monoxide in man, there is little information on the behavioral incapacitation resulting from short exposures to high concentrations likely to be encountered in fires. Monkeys, trained to perform behavioral tasks during exposures to 900 ppm carbon monoxide, were seriously affected after 20 to 30 min exposure, achieving carboxyhemoglobin levels of 25-30%. The tests were as sensitive as tests in man for detecting psychomotor deficits induced by carbon monoxide, and measurements of carbon dioxide production presented a more sensitive method for detecting early deficits. It is concluded that a man exposed to 1000 ppm carbon monoxide while engaged in light activity (e.g., walking) could be seriously affected within 30 min.     

Human factors in firefighting: ergonomic-, cardiopulmonary-, and psychogenic stress-related issues

Summary There are many issues in firefighting that involve human factors and cardiopulmonary conditioning. Population-based mortality and disability surveillance studies suggest a relatively small but significant excess of disability but not mortality from nonmalignant cardiovascular disease for fire fighters. More targeted cohort and case-control studies do not support such an excess and instead suggest a strong healthy worker effect. Pulmonary function among fire fighters has been extensively studied, with contradictory findings. Extreme exposures and long-term exposure in combination with cigarette smoking may be risk factors for respiratory disorders and accelerated decline in airflow. It appears likely that individual fire fighters who show early signs of illness are often selectively transferred out of active firefighting positions. Despite exposure to substances such as carbon monoxide that may predispose to cardiovascular mortality and morbidity, excesses are not consistently shown in mortality studies. Clinical studies of individual fire fighters do suggest an elevated risk for myocardial ischemia. The ergonomic demands of firefighting are extreme at peak activity because of high energy costs for activities such as climbing aerial ladders, the positive heat balance from endogenous and absorbed environmental heat, and encumbrance by bulky but necessary protective equipment. The psychological stresses of firefighting include long periods of relative inactivity punctuated by highly stressful alarms and extremely stressful situations such as rescues, as reflected in physiological and biochemical indicators. Fire fighters are at risk for depression and posttraumatic stress disorder, although morale overall is generally much higher than in comparable occupations. Women firefighter candidates as a group perform less well on selection test simulating the demands of active firefighting, but some individual women perform very well.     

Smoke inhalation: an ultrastructural study of reaction to injury in the human alveolar wall

This study was undertaken to determine the site of initial pulmonary injury in smoke inhalation. A hotel fire in Houston, Texas, resulted in the on-site deaths of 10 white people (2 to 62 years of age). All underwent autopsy examinations which included measurement of carbon monoxide (CO) and cyanide (CN) levels, as well as electron microscopy of lung samples. Average CO levels of 40% and CN levels of 0.6 ppm were obtained. In all cases, the lungs were heavy, hyperemic, and edematous with soot staining the tracheobronchial mucosa. Light microscopy showed soot, pulmonary congestion, and edema. Electron microscopy confirmed the presence of interstitial and intraalveolar congestion and edema. Carbon particles were also present, and occasionally were seen undergoing phagocytosis by alveolar macrophages. Intracellular edema with focal bleb and vesicle formation was prominent within Type I pneumocytes in 9 of 10 cases. Endothelial cells showed similar but much less severe changes, lacking the distinct blebs seen in the Type I cells. This investigation reveals that smoke, like ammonia inhalation and nitric acid instillation, appears to cause pulmonary edema by initial injury to the Type I pneumocyte.     

Validation of self-reported smoking status by simultaneous measurement of carbon monoxide and salivary thiocyanate

OBJECTIVE: The objective of this study was to determine the validity of tobacco questionnaires when using as gold standard either a single biomarker or a combination of two biomarkers. METHODS: The methods were self-reported smoking compared with salivary thiocyanate and expired carbon monoxide in a 1996, population-based, Swiss survey of 552 men and 565 women. RESULTS: Sensitivity of self-reported smoking relative to salivary thiocynate or carbon monoxide alone was low (38.2% for salivary thiocyanate > or = 100 mg/L, 56.4% for salivary thiocyanate > or = 150 mg/L and 62.6% for carbon monoxide > or = 9 ppm). When defining true positive smokers as people with high concentration of both salivary thiocyanate and carbon monoxide, overall, sensitivity was 88.6% and specificity was 87.2%. In women, sensitivity increased from 85 to 89% when removing subjects exposed to passive smoking. When excluding heavy smokers, sensitivity decreased to 63% in men and to 71% in women. Older women had tendency to misreport smoking. CONCLUSIONS: This comparison of questionnaire data with the simultaneous measurement of salivary thiocyanate and expired carbon monoxide indicates that valid responses can be obtained for self-reported, current smoking in population-based surveys. However, the validity of questionnaires can be underestimated if the gold standard (of exposure to tobacco smoke) is either high levels of carbon monoxide or high levels of salivary thiocyanate.     

Injuries on the fireground: risk factors for traumatic injuries among professional fire fighters

This case-control study within a metropolitan fire department evaluated the effect of self-contained breathing apparatus (SCBA) and other risk factors on three types of injury at the scene of a fire (smoke inhalation, burns, and falls). Data on 75 injured fire fighters and 144 controls came from telephone interviews and department records. The two sets of uninjured fire-fighter controls were matched to cases on incident (n = 72) or on job position and fire type and size (n = 72). Smoke inhalation cases were not significantly different from controls in SCBA use, cigarette smoking, previous fires in the shift, or injury history. Jobs with high risk of burns included nozzle operator, engine officer, and forcible-entry person in first-due companies (OR = 20.1). Other risk factors for burns were: basement origin of fire (OR = 10.2); prior fire-fighting training outside the present department (same fire: OR = 11.2; similar fire: OR = 3.9); and on-duty injury in the prior 12 months (same fire: OR = 4.3; similar fire: OR = 3.5). When other risk factors were considered, consistent SCBA use was associated with falls (same fire: OR = 11.8; similar fire: OR = 4.3) but not with burns. Risk of falls also was elevated among members of truck companies (OR = 17.7) and fire fighters without children (same fire: OR = 8.4; similar fire: OR = 7.4). On-duty injury in the past 12 months was associated with falls when one compared cases with similar-fire controls (OR = 5.5), but not with controls attending the same fire. Neither age nor experience was related to injury in this population.     

Respiratory Irritants in Australian Bushfire Smoke: Air Toxics Sampling in a Smoke Chamber and During Prescribed Burns

Bushfire smoke contains an array of organic and inorganic compounds, including respirable and inspirable particles, aldehydes, and carbon monoxide. These compounds have been found to be a health hazard for firefighters in the United States. Despite the high frequency of bushfires in Australia, analyses of bushfire smoke components are scarce. As part of an occupational health study investigating the respiratory health effects of bushfire smoke in firefighters, air toxics sampling was undertaken in a smoke chamber and during prescribed burns. Levels of formaldehyde and acrolein were demonstrated at respectively 60% and 80% of the Short Term Exposure Limit in the smoke chamber. Carbon monoxide levels exceeded the peak limit of 400 ppm significantly. Although concentrations were lower during the prescribed burns, the study shows that Australian bushfire smoke contains air toxics of concern and provides justification for further research into the levels of air toxics measured at bushfires and the associated health impacts.     

Annoyance and irritation by passive smoking

The acute irritating and annoying effects of smoke have been investigated in field and laboratory studies by examining the concentration of some smoke components in air. In the workplace, 30 to 70% of the indoor carbon monoxide, nitrogen oxide, and particulate concentrations are due to tobacco smoke; 25-40% of the employees are disturbed and/or annoyed by smoke and 25% suffer from eye irritation at work. Subjective eye, nose, and throat irritations and eye blink rate increase with increasing smoke concentration and increasing exposure duration. Irritation is due mainly to the particulate phase of environmental tobacco smoke, whereas the gas phase is, to a large extent, responsible for annoyance. It is concluded that healthy individuals can tolerate an environmental tobacco smoke level that corresponds to a carbon monoxide concentration of 1.5 to 2.0 ppm. Above these limits, countermeasures to protect passive smokers are necessary. In order not to exceed the upper tolerable threshold limit of 2.0 ppm carbon monoxide, it is necessary to have a fresh air supply of 33 m3 per hour per cigarette smoked. Special attention should be paid to groups of people with increased sensitivity to environmental tobacco smoke, e.g., asthmatics, allergic individuals, chronic bronchitis sufferers, and children.     

A longitudinal study of pulmonary function in fire fighters

Pulmonary function changes among fire fighters were evaluated by re-examining 632 Baltimore city fire fighters six to ten years after a baseline examination. Spirometry was used to determine forced expiratory volume in 1 second (FEV1). Information about exposures was obtained by questionnaire and by combining data from fire department records regarding the number of fires fought by fire fighting units with individual work histories. Men who never wore a mask while extinguishing fires experienced a 1.7 times greater rate of FEV1 decline than mask wearers. Men with ammonia exposure experienced a rate of decline 1.7 times greater than non-exposed men. Neither length of time spent in exposed jobs nor number of responses were associated with the rate of decline. Active fire fighters experienced a rate of decline 2.5 times greater than those who had retired or resigned. Some effects differed between men who were able to perform repeatable pulmonary function tests and those who were not.     

Air Pollution in Native Huts in the Highlands of New Guinea

The degree of air pollution in native huts in the New Guinea Highlands has been assessed The “average” concentrations of smoke density, aldehydes, and carbon monoxide measured in the Eastern Highlands, at an altitude of 7,200 feet, were 666 μg/m³ 1.08 ppm and 21.3 ppm, respectively, but these figures do not include peak values of 4,862 μg/m³, 3.8 ppm and 150 ppm which were obtained on one occasion soon after startup of the fire. Comparable “average” values in the Western Highlands, at 4,000 to 5,200 feet were 359 μg/cum, 0.67 ppm and 11.3 ppm, respectively.

Smoke density was highly correlated with aldehyde concentrations in both areas, r = +0.93 and + 0.88, and with carbon monoxide, r = + 0.87 and +0.72.

Air pollution may be a contributing factor in the genesis and maintenance of the prevalent nontuberculous lung disease in New Guinea highlanders.     

Heart rates in fire fighters using light and heavy breathing equipment: similar near-maximal exertion in response to multiple work load conditions

Intense exertion is an occupational hazard inherent to fire fighting. This study was designed to look at the exertion levels that fire fighters attain during a fire fighting exercise when using (1) no self-contained breathing apparatus (SCBA), (2) light SCBA, and (3) heavy SCBA. Exertion levels were measured as a function of the heart rate increase relative to the maximum predicted heart rate determined by a standard treadmill exercise test. Five fire fighters wore electrocardiographic monitors during a routine fire fighting exercise. Heart rates increased rapidly to 70% to 80% of maximum within the first minute and then plateaued at 90% to 100% until the attack on the fire was completed. There was no significant difference between exertion levels when using no SCBA, light SCBA, and heavy SCBA (split-plot analysis of variance, p greater than .25). These results suggest that fire fighters attain an intense level of physical activity quickly and maintain that level as long as they are actively engaged in fighting fire. These results also suggest that regardless of the weight of the SCBA, if employed, fire fighters exert themselves from 85% to 100% of their maximum and adjust their work output to maintain that near-maximal level.     

Smoky indoor cooking fires are associated with elevated hemoglobin concentration in iron-deficient women.

OBJECTIVE: Indoor air pollution from the burning of such biomass fuels as wood and agricultural waste is associated with a higher risk of a number of respiratory problems. The effect on other health outcomes, such as fetal growth, has not yet been adequately documented. The objective of this study was to determine whether, among women who burn biomass fuels for cooking indoors, the use of "smoky" fires is associated with elevated hemoglobin concentration in comparison to women using "smokeless" stoves, that is, stoves that are designed to reduce indoor air pollution. This research was conducted as part of a series of preliminary studies to determine the feasibility and potential health benefits of a randomized stove intervention to reduce indoor air pollution from the burning of biomass fuels for cooking. METHODS: A cross-sectional observational study was conducted in rural highland communities of Guatemala from March to August 1994. Venous blood samples were collected and analyzed for hemoglobin and ferritin. All the women studied burned biomass fuels and cooked indoors, and none of the women was pregnant. Eighty-nine indigenous women using smokeless stoves (designated as the not-exposed group) and 185 indigenous women from the same communities using smoky fires (the exposed group) were studied. Multiple linear regression analyses were used to investigate the relationship between exposure (smokeless stove or smoky fire) and hemoglobin concentration, with adjusting for potential confounding factors. RESULTS: No effect of exposure (smokeless stove or smoky fire) on hemoglobin concentration was found in univariate or multivariate analyses. In routine post hoc analysis to determine whether hemoglobin elevation is observed in some particular subgroup, we found that the use of a smoky fire was associated with a 5.2 g/L elevation in hemoglobin concentration among women with low ferritin stores (P < 0.10). CONCLUSIONS: The elevation of hemoglobin concentration through exposure to indoor air pollution resulting from the burning of biomass fuels in smoky fires for cooking could have important implications for the diagnosis of anemia. However, considering the observational nature of this study, further research using more rigorous measures of exposure to carbon monoxide as well as additional measures of iron status are needed to confirm the relationships among iron status, exposure to smoke from the burning of biomass fuels indoors, and hemoglobin concentration of women living at moderately high altitude. Further study of this matter could help to assure that appropriate adjustments to anemia cutoffs are made, if warranted, and could assist in clarifying potentially negative outcomes of exposure to smoke from biomass fuels burned indoors.