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Fatal Work-Related Inhalation of Harmful Substances in the United States^*

^* From the Epidemiology Unit (Dr. Valent), Center for Injury Sciences; the Section of Trauma, Burns, and Surgical Critical Care (Dr. McGwin), Division of General Surgery, Department of Surgery; and Department of Epidemiology and International Health (Dr. Barbone), School of Public Health, University of Alabama at Birmingham, Birmingham, AL; and the Clinical Unit of Occupational Medicine (Dr. Bovenzi), Department of Public Health Sciences Trieste General Hospital, University of Trieste, Italy.

Correspondence to: Gerald McGwin, Jr., MS, PhD, Center for Injury Sciences, 120 Kracke Building, 1922 7th Ave South, University of Alabama at Birmingham, Birmingham, AL 35294-0016; e-mail: gerald.mcgwin{at}ccc.uab.edu

	Abstract

TOP Abstract Introduction Materials and Methods Results Discussion Conclusion References

 
Study objectives: Inhalation of harmful substances is common in the workplace. The purpose of this study was to describe the epidemiology of fatal occupational inhalations in the United States.

Design: Data from the Census of Fatal Occupational Injuries from 1992 to 1998 were analyzed. Information on demographic characteristics, occupation, and industry was used to calculate specific mortality rates, and the inhaled substances were identified.

Results: Nationwide, there were 523 cases of fatal occupational inhalation, with a mortality rate of 0.56 deaths per 1,000,000 worker-years. The rate of death was greater for men (1.01/1,000,000) than for women (0.03/1,000,000), and workers 65 years of age had the highest mortality. Mining was the industry with the highest mortality rate (6.64/1,000,000). The occupations with the highest rate were firefighters (3.54/1,000,000) and farming, forestry, and fishing occupations (2.84/1,000,000). Nearly half of the inhalation victims were constructing, repairing, cleaning, inspecting, or painting when the injury occurred. Overall, carbon monoxide was the most frequently inhaled substance (33.5%). The incidence of fatal carbon monoxide inhalations was twice as high in the winter as in the summer. The proportion of workers killed by carbon monoxide poisoning increased with increasing age.

Conclusions: Work-related inhalations cause more deaths than any other mode of exposure to harmful substances. Recognizing those circumstances that pose a higher risk for maintenance and repair workers, as well as upgrading carbon monoxide poisoning prevention programs, could have a major impact in reducing fatal work-related inhalation injuries.

Key Words: carbon monoxide • Census of Fatal Occupational Injuries • industry • inhalation • injury • mortality • occupation • occupational exposure source

	Introduction

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Inhalation is a common manner of exposure to harmful substances in the workplace. In the United States, in each year from 1992 to 1998, the United States Department of Labor, Bureau of Labor Statistics (BLS) reported an average of > 11,000 nonfatal injuries and illnesses involving days away from work, caused by occupational exposure to harmful substances through the respiratory tract.¹ In the same years, the BLS also reported an annual average of 68 deaths following job-related inhalations.² Inhalations represented < 23% of the nonfatal injuries caused by exposure to caustic, noxious, or allergenic substances,¹ but they accounted for > 58% of harmful substance-related deaths.²

In a study of nonfatal work-related inhalations based on a probability sample of hospital emergency departments in the United States, Henneberger et al³ estimated the national number of cases and rates, as well as identified the categories of subjects, the industries at high risk of inhalation, and the sources of injury. According to that study, male and young workers experienced the highest rates of nonfatal inhalations, public administration and transportation/public utilities appeared to be high risk industries, and the most frequently inhaled substances were: (1) carbon monoxide, carbon dioxide, and engine exhaust; (2) fire smoke; (3) minerals; (4) bleach; (5) acids and ammonium compounds; (6) plastics, paints, and solvents; and (7) chlorine. Findings regarding nonfatal inhalations should not be generalized to fatalities, because death rates are influenced not only by injury rates, but also by injury severity and other factors affecting postevent survival. Epidemiologic data describing fatal occupational inhalations in the United States have not been published. Adekoya and Myers⁴ studied fatal events resulting from exposure to harmful substances or environment, but their analysis was restricted to agriculture.

The purpose of our study was to conduct a comprehensive analysis of fatal occupational injuries due to inhalation of harmful substances in the United States. The demographic characteristics of the injured workers, the frequency of inhalation in specific occupations and industries, and the substances that produced the injury were evaluated.

	Materials and Methods

TOP Abstract Introduction Materials and Methods Results Discussion Conclusion References

 
Fatal occupational injuries in the United States from 1992 to 1998 were analyzed using the BLS Census of Fatal Occupational Injuries (CFOI). The CFOI is a federal/state cooperative program, implemented in all 50 states and the District of Columbia since 1992, which monitors fatal work injuries in the United States through a national census approach. The CFOI uses multiple sources to identify fatal worker injuries. Information about each occupational death is obtained by cross-referencing the records from several sources, such as death certificates, workers’ compensation reports, coroner, medical examiner and autopsy records, Occupational Safety and Health Administration (OSHA) fatality reports, the Mine Safety and Health Administration, the Employment Standards administration, news media, follow-up questionnaires, state motor-vehicle crash reports. To determine whether a fatality is work related, state personnel who collect, code, and verify fatality data use a case definition that stipulates that "the decedent must have been employed (that is, working for pay, compensation, or profit or in the family business) at the time of the event and engaged in a legal work activity or present at the site of the incident as a requirement of his or her job."⁵ Suicides and homicides meet the case definition if they occur at work. Fatalities that occur while traveling to and from work (commuting) are not considered work related. In general, each fatality must be verified by two source documents. In those instances where a second source document cannot be located, the fatality is included only if sufficient information exists from the first source to determine that the fatality was work related.^{2 5}

In the CFOI data files, the event or exposure that produced the injury and the source of injury are coded using the Occupational Injury and Illness Classification Structures (OIICS).⁶ Occupation is coded according to the Census Occupation Classification System (COCS), 1990.⁷ Industry is coded according to the Standard Industrial Classification Manual (SIC), 1987 Edition.⁸

For this study, we selected fatal occupational events classified by OIICS as inhalation of substance (codes 3410 through 3412). In addition, for event codes 3000 (exposure to harmful substances or environments, unspecified), 3400 (exposure to caustic, noxious, or allergenic substances, unspecified), 3490 (exposure to caustic, noxious, or allergenic substances, not elsewhere classified), 3800 through 3890 (oxygen deficiency, not elsewhere classified), 3900 (exposure to harmful substances or environments, not elsewhere classified), 9000 (other events or exposures), and 9999 (nonclassifiable), we reviewed the narratives describing the circumstances of the injury. Those cases for which the verbal description was consistent with an occupational inhalation were added to our study (48 subjects). Both inhalations in enclosed, restricted, or confined space and inhalations in open or nonconfined space were included in the analysis. Suicides and homicides were excluded from this study.

Mortality rates were calculated using denominators derived from the 1990 and 1998 Current Population Survey (CPS) files.⁹ The CPS is a Census Bureau survey of the noninstitutionalized population of the United States and the standard source of national data on employment. The CPS does not include persons on active duty in the armed forces. To have comparable death rate numerators and denominators, we excluded from our study six fatal occupational injuries that occurred to subjects whose occupation was "military" (COCS codes 903 to 905). Rates were expressed as deaths per 1,000,000 worker-years. In addition, a descriptive analysis was performed of the chemical and nonchemical sources of fatal inhalations.

	Results

TOP Abstract Introduction Materials and Methods Results Discussion Conclusion References

 
In the United States, from 1992 to 1998, 523 civilian workers died as a result of the inhalation of harmful substances. The mortality rate was 0.56 deaths per 1,000,000 worker-years. Inhalation was the most common manner of fatal occupational exposure to caustic, noxious, or allergenic substances. Nationally, in the same period, only 25 persons died on the job as a consequence of a skin/tissue contact with harmful substances; 86 workers were killed by injections, stings, and venomous bites; and 121 fatally injured subjects were exposed to the harmful substance through ingestion.

Demographic Characteristics
Table 1 shows the demographic characteristics of the victims of inhalations and the mortality rates. Only 13 fatal inhalation cases (2.5%) were in female subjects. The mortality rate was greater among men than among women (rate ratio, 33.67). Almost 60% of all the subjects who died from fatal inhalation were between 25 years and 44 years of age. However, the highest death rate was found among workers 65 years old. White workers had the highest mortality rate, and they accounted for nearly 85% of the cases.

Worker Activities and Locations
The activities workers were doing at the time of fatal inhalation are shown in Table 5 . Almost 40% of the fatal inhalations (n = 204) occurred at industrial places. Of these, 22 fatal inhalations took place at construction sites. Sixty-four fatal inhalations occurred in farms. In particular, 11 fatal inhalations occurred in silos and grain bins and 22 occurred in other farm buildings.

	Discussion

TOP Abstract Introduction Materials and Methods Results Discussion Conclusion References

Our finding that women had lower mortality rates than men is consistent with what reported by Henneberger et al³ about nonfatal work-related inhalations, although the difference between genders was much greater in our study. In fact, using the National Electronic Injury Surveillance System (NEISS), Henneberger et al³ estimated that > 30% of the individuals who visited hospital emergency departments because of occupational inhalations were women, and that the incidence rate among male patients was less than twice that among female patients. Dissimilarly, in our study, < 3% of the victims were women and the mortality rate among male patients was > 30 times as great as among female patients. A possible explanation for the discrepancy between fatal and nonfatal inhalations is the difference between the sources of data used in the two studies. In fact, a surveillance system based on hospital emergency care captures events of different severity, and if women are more prone than men to seek care after an injury occurred, nonsevere cases among male patients might have been underrepresented in the NEISS sample. On the contrary, since death was the outcome of interest in our study, this hypothesized differential reporting of the event was less likely. In addition, it is likely that the sensitivity of the CFOI system is high as compared to the NEISS system, because multiple data sources are used to identify fatal worker injuries.⁵ However, part of the discrepancy of gender differences between fatal and nonfatal inhalations could be real. An explanation could be a different exposure opportunity between male and female workers. For example, women might be assigned to environments with lower concentrations of toxic substances or where the substances they are exposed to have a lower degree of toxicity, or they might hold jobs requiring less hazardous tasks. Or, alternatively, female workers might be more willing to adopt safety measures than male workers.

We found that workers 65 years old had the highest mortality rate from inhalations. This is consistent with other studies. A high rate of fatal occupational exposures to harmful substances and environments among the elderly was reported by Adekoya and Myers⁴ in agriculture. Kisner and Pratt¹⁰ identified workers 65 years old as having the highest mortality rate for job-related injuries. Several factors could contribute to the higher mortality in elderly workers, such as comorbidities worsening the harmful effect of inhaled substances, or physical impairments increasing the overall likelihood of injury or preventing a quick escape in case of danger, or possibly a reduced use of safety devices. Henneberger et al³ reported that the rate of nonfatal inhalations declined with increasing age, but the oldest age group in their study included all workers 45 years old. Therefore, our results are not comparable. In our study, consistent with what reported by Henneberger et al,³ similar mortality rates were found among white and black workers.

We identified industries and occupations with high rates of fatal inhalations, as well as the substances associated with the injuries in each industry. Carbon monoxide was more frequently involved than any other substances in fatal inhalations. Our data on fatal carbon monoxide inhalation are consistent with estimates of severe nonfatal inhalation cases as estimated by emergency department visits requiring hospitalization.³ However, the NEISS study found that irritants, particularly chlorine gas and chlorine compounds, were the most common sources of emergency department visits not requiring hospitalization. Our results confirm that the relatively high incidence of severe cases of unintentional carbon monoxide inhalation continues to be a problem in the United States, particularly during the winter.¹¹ We found that carbon monoxide poisoning was the most common cause of death among older workers. This means that either fatal inhalations of substances other than carbon monoxide were less common among the elderly than among younger workers, or carbon monoxide intoxication occurred more frequently in the oldest age group. The latter possibility is compatible with a higher lethality of carbon monoxide exposure in the elderly. In fact, the higher prevalence of atherosclerosis among the elderly makes their organs more susceptible to carbon monoxide toxicity.

Exposure to carbon monoxide was a major problem across industries, and in most cases it was not the result of being trapped in a fire. In fact, we included in our study only those fatal injuries in which the reported event or exposure was an inhalation or an unspecified exposure to harmful substance or environment when the narrative of how the injury occurred described an inhalation without doubts. In this way, victims of fires and explosions (OIICS event codes 5000 through 5290) did not match our case definition, even though, in addition to burns and other lesions, inhalation of smoke and/or carbon monoxide had almost certainly occurred. Therefore, the majority of carbon monoxide poisonings analyzed in this study were the consequence of defects and malfunctioning of vehicles, machines or tools, such as propane powered machines or heaters, or were the result of improper worker behavior, such as working on/with vehicles with motor running in closed and unventilated environments. Considering all of this, as Ely et al¹² pointed out, awareness of the various occupational settings in which exposures to carbon monoxide can occur is a fundamental requirement to prevent serious intoxications.

As compared to carbon monoxide, exposure to other substances was more industry specific, and preventive strategies must address industries individually. The Centers for Disease Control and Prevention had identified mining, agriculture, forestry, and fishing, and construction as the industries with the highest rates of fatal occupational injuries overall, based on the 1980–1994 data from the National Traumatic Occupational Fatalities surveillance system.¹³ In this study, we found that the same industries had the highest rates of fatal inhalations. In addition, we identified the auto and miscellaneous repair services to be an industry with increased inhalation mortality rate.

Nearly one fourth of the victims were doing repair or maintenance activities when the fatal inhalation occurred, and almost one tenth were cleaning or washing. This indicates that unspecific job titles such as maintenance, repair, janitorial or cleaning tasks often entail a high risk for this type of injury. In particular, repairing damaged structures or malfunctioning machines might be a dangerous activity if the damage or malfunctioning itself is the cause of a leak of harmful substances. Moreover, cleaning activities might become hazardous if the workers are not properly equipped, trained, and aware of the characteristics of their job environment.

Using the CFOI had a number of advantages. compared to using death certificates alone, the CFOI is more sensitive because it is based on multiple reporting sources.^{5 14 15 16} Its positive predictive value is also probably high, since approximately three fourths of the cases reported to the CFOI have a death certificate as one of their source documents, and each fatality must be verified by two source documents.⁵ The CFOI is also considered as a representative surveillance system for fatal occupational injuries in the United States because of the multiple source of information. Even fatal injuries to workers not covered by the Occupational Safety and Health Act, governmental employees, workers on small farms, and workers < 16 years old can be captured by sources such as death certificates, coroner records, motor-vehicle crash reports, and news stories.⁵ However, the CFOI might underestimate fatalities of self-employed workers not represented in workers’ compensation or OSHA reports.⁵

The CFOI data also include a brief narrative of how the injury had occurred. This could be a very useful tool for the assessment of other factors contributing to inhalations at work. Unfortunately, the quantity and quality of the information reported in such narratives was extremely heterogeneous, at least for the 523 cases we studied, ranging from a few words adding no information to the rest of the data, to longer and detailed descriptions of the event. Some detailed descriptions reported, for example, the use of safety equipment, the number of persons involved in the same event, or the victim’s intent before the injury occurred.

	Conclusion

TOP Abstract Introduction Materials and Methods Results Discussion Conclusion References

 
Every year, approximately 65 people die because of a work-related inhalation in the United States. This mode of exposure causes more occupational deaths than any other exposure to harmful substances. Industry-specific preventive measures should be implemented to address exposure to industry-specific substances. General safety procedures should be monitored to reduce the higher toll paid by maintenance and repair workers. The industry-wide relevance of carbon monoxide poisoning requires enforcement of carbon monoxide preventing measures. These measures include ventilation safety especially during the winter, dissemination of carbon monoxide-monitoring programs and symptoms identification. Education about the higher risks encountered by especially susceptible subjects should be common practice for elderly workers.

	Footnotes

 
Abbreviations: BLS = Bureau of Labor Statistics; CFOI = Census of Fatal Occupational Injuries; COCS = Census Occupation Classification System; CPS = Current Population Survey; NEISS = National Electronic Injury Surveillance System; OIICS = Occupational Injury and Illness Classification Structures; SIC = Standard Industrial Classification Manual

The work was performed at the University of Alabama at Birmingham, Birmingham, AL.

	References

TOP Abstract Introduction Materials and Methods Results Discussion Conclusion References

 

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2. U.S. Department of Labor. Safety and health statistics. Census of Fatal Occupational Injuries (CFOI). Washington, DC: Bureau of Labor Statistics. Available at: http://stats.bls. gov/iif/oshwc/cfoi/cftb138.txt. Accessed January 23, 2001
3. Henneberger, PK, Metayer, C, Layne, LA, et al (2000) Nonfatal work-related inhalations: surveillance data from hospital emergency departments, 1995–1996. Am J Ind Med 38,140-148[CrossRef][ISI][Medline]
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8. Standard industrial classification manual 1987. 1987 U.S. Executive Office of the President, Office of Management and Budget Washington, DC.
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