26 Compensation and Working Conditions Fall 1998

Job Fatalities Due

to Unintentional

Carbon Monoxide

Poisoning, 1992-96

Safety and Health

In any given year, numerous deaths

result from accidental exposure

to carbon monoxide

poisoning.

CHRISTOPHER A. JANICA K

Christopher A. Janicak is an assistant professor of safety, Illinois State University, Normal, IL. The author’s views are his own and do not necessarily

reflect those of the Bureau of Labor Statistics or the U.S. Department of

Labor.

Telephone: (309) 438-7237

E-mail: cajanic@ilstu.edu

Carbon monoxide is a clear, colorless, odorless toxic gas

that is a product of incomplete combustion. It is one of

many chemicals found in engine exhaust. Carbon monoxide can rapidly accumulate even in areas that might appear

to be well ventilated. Carbon monoxide combines with hemoglobin to form carboxyhemoglobin which interferes with

the oxygen-carrying capacity of blood, resulting in a state

of tissue hypoxia.1 Carbon monoxide exposure levels of

80–100 parts per million (ppm) for 1 to 2 hours can create

adverse health affects. The concentration that the National

Institute of Occupational Safety and Health (NIOSH) considers immediately dangerous to life and health is 1,200

ppm.2 The Occupational Safety and Health Administration has set permissible exposure levels to 50 ppm for an 8-

hour time weighted average.3

Carbon monoxide poisoning is common in the United

States with an estimated 10,000 persons seeking medical

attention or missing at least 1 day of normal activity each

year because of it.4

 In any given year, numerous deaths

result from the accidental exposure to this toxic gas. Studies from the Center for Disease Control indicate that there

are as many as 600 deaths annually in the United States

due to unintentional carbon monoxide poisoning.5 The

Bureau of Labor Statistics (BLS) estimates that there were

867 nonfatal poisonings requiring time away from work to

recuperate and 32 fatal poisonings in private industry in

the United States in 1992.6

Most fatal unintentional carbon monoxide poisonings

are associated with motor vehicles and are preventable.

Exposure can result from these primary sources: The operation of a motor vehicle with a faulty exhaust system or

an inadequately ventilated passenger compartment; the operation of a motor vehicle in an enclosed space; and the use

of auxiliary fuel burning heaters.7

Other studies have identified various pieces of power

equipment as the primary sources for a number of carbon

monoxide deaths. Examples of such equipment include

power washers, space heaters and generators.8

Safety standards are in place that are designed to minimize a person’s exposure to lethal levels of carbon monoxide in the workplace. These standards establish protection

requirements and limit the levels of carbon monoxide a

person may be exposed to. While these standards are effective in reducing the potential for carbon monoxide poisoning, many cases still result from activities that are not recognized as hazardous by the victims.

The purpose of this study is to identify the industries

and activities that most often result in carbon monoxide

poisoning. By identifying these situations, prevention measures can be developed and directed to those who would

benefit the most.

Unintentional carbon monoxide poisonings

From January 1, 1992 through December 31, 1996, unintentional carbon monoxide poisonings caused 148 fatalities. The service sector accounted for the largest share of

the fatalities, 25 percent. (See table 1.) Within this sector,
 Compensation and Working Conditions Fall 1998 27

Carbon Monoxide Poisoning

automotive repair, services, and parking industries accounted for almost half of the unintentional carbon monoxide deaths.

Proportionate mortality ratios identified three industries

with proportions of deaths due to carbon monoxide poisoning that were significantly different than what was expected.

(See table 2.) The transportation industry had significantly

fewer carbon monoxide deaths than expected while the services industry and the nonclassifiable industries had significantly more.

The services sector includes vehicle repair and vehicle

maintenance occupations. Employees in these occupations

who died from carbon monoxide poisoning were most often overcome by fumes while they were maintaining or repairing a vehicle with the engine running in an enclosed

space.

In the nonclassifiable industries, the majority of deaths

also involved automobile exhaust. Victims were most often found dead in, or near, a vehicle with a running engine.

Gasoline powered equipment such as power saws, pumps,

and space heaters accounted for the majority of the remaining deaths. In most instances, the victims were using the

equipment in an enclosed space.

Prevention strategies

Occupational fatalities caused by unintentional carbon monoxide poisoning accounted for approximately 5 percent of

all fatal unintentional carbon monoxide poisonings in the

United States during the period 1992-96. Prevention strategies for these types of deaths should include the incorporation of both engineering and administrative controls.

Engineering controls include the use of carbon monoxide detectors like those used in private homes. Their use

should be expanded to the workplace especially to automobile repair and maintenance facilities. It would not be unreasonable to incorporate the installation of carbon monoxide detectors into the building codes for those occupancies

that might be exposed to potentially lethal concentrations

of carbon monoxide. Engineering controls should also include the use of ventilation systems that attach to the exhaust pipe of a vehicle and safely discharge exhaust fumes

to outside air. The cost of this equipment is small and the

benefits would include a reduction in the number of fatal

and nonfatal carbon monoxide poisonings that occur each

year in the workplace.

Administrative controls should include the development

and enforcement of safety policies and procedures. Working on running vehicles in enclosed areas without proper

ventilation should be prohibited.

A number of deaths occurred when the victims were

working alone on a vehicle after normal work hours. Prohibiting this practice or assigning a second person to be

available outside of the workspace to periodically check on

the person performing the work, could prevent some deaths.

Other deaths resulted from the use of various types of

gasoline powered equipment such as cement cutters and

generators. Prevention strategies for these types of equipment should include their proper maintenance and use.

When equipment is not running efficiently, the incomplete

combustion process tends to release higher concentrations

of carbon monoxide. Equipment should be used with adequate ventilation and, if necessary, proper personal protective equipment including a self-contained breathing

apparatus. Maintaining equipment will help reduce the levels of carbon monoxide released during combustion.

Finally, employee training should be conducted to inform employees about the hazards of carbon monoxide poisoning. Studies show that potentially lethal levels of carbon monoxide can be reached in a matter of seconds when

small gasoline powered engines are running in enclosed

spaces. People do not fully understand the hazards of carbon monoxide or the situations that can produce lethal carbon monoxide levels. Training should include the identification of equipment and job tasks that present a carbon

monoxide hazard, the proper use of gasoline powered equipment and personal protective equipment, and a review of

all employer provided hazard control policies and equipment.

Methodology

Data. This study used BLS data from the Census of Fatal

Occupational Injuries (CFOI). The CFOI is an official, systematic, verifiable count of fatal occupational injuries that

occur during the year.9

 It has been adopted by the National

Safety Council and other organizations as the authoritative

source for a count of fatal work injuries in the United States.

To ensure that the fatalities are work related, cases are

substantiated with two or more source documents or a source

document and a follow-up questionnaire. Work-related

deaths are classified as such if a working relationship has

been established. A working relationship is established if

an employee is on the employer’s premises to work, the

employee is off the employer’s premises but there to work,

TABLE 1. Unintentional carbon monoxide fatalities by industry,

1992-96

Number Percent

of deaths of total

 Total .................................. 148 100.0

Agriculture ............................. 21 14.2

Mining .................................... 5 3.4

Construction .......................... 21 14.2

Manufacturing ........................ 22 14.9

Transportation........................ 7 4.7

Wholesale trade .................... 4 2.7

Retail trade ............................ 11 7.4

Finance, insurance, and

 real estate ............................ 4 2.7

Services ................................ 37 25.0

Public administration ............. 9 6.1

Nonclassifiable ...................... 7 4.7

Industry

1

1

 Nonclassifiable includes establishments which cannot be

classified in any other industry.
28 Compensation and Working Conditions Fall 1998

or the event or exposure is related to the person’s work or

status as an employee.

This study analyzed deaths that occurred from January

1, 1992 through December 31, 1996 as a result of carbon

monoxide poisoning. Deaths classified as self-inflicted were

removed from the analysis. This ensured that the 148 cases

selected were unintentional and not suicides that occurred

at work. For each case, the industrial classification, date of

the event, and narrative description of the event were analyzed. The cases were classified according to their major

standard industrial classification groups following the methodology outlined in the Standard Industrial Classification

Manual 1987.10

Proportionate mortality ratios. A proportionate mortality ratio (PMR) was calculated for each industry classification following the procedures described by

Spiegelman, Wang, and Wegman11 and Mantel and

Haenszel.12 Proportionate mortality ratios compare the

observed fatalities in a group to the expected number of

fatalities for a particular reason. The expected number

of fatalities is derived from the fatality experience for

the entire population. In this study, the observed number of fatalities due to carbon monoxide poisoning for

each industry was compared to a statistically expected

number of fatalities based upon the proportions of all

fatalities for all industries.

Mantel-Haenszel Chi-square tests of significance. Mantel-Haenszel Chi-square tests of significance were performed

to determine if the observed deaths were significantly different from what could be expected.

 Total ......................................................................... 31,323 148

Agriculture .................................................................... 4,050 21 19.1 16.6 0.11 109.7

Mining ........................................................................... 844 5 4.0 3.9 .07 125.4

Construction ................................................................. 5,072 21 24.0 20.0 .60 87.6

Manufacturing ............................................................... 3,751 22 18.0 15.5 .92 124.1

Transportation............................................................... 4,880 7 23.0 19.4 14.151 30.4

Wholesale trade ........................................................... 1,306 4 6.2 5.9 1.21 64.8

Retail trade ................................................................... 3,699 11 17.5 15.3 3.17 62.9

Finance ........................................................................ 598 4 2.8 2.8 .16 141.6

Services ....................................................................... 4,297 37 20.3 17.4 15.051 182.2

Public administration .................................................... 2,449 9 11.6 10.6 .89 77.8

Nonclassifiable ............................................................. 377 7 1.8 1.8 12.711 393.0

Carbon

monoxide

deaths

Expected

carbon

monoxide

deaths

Proportionate

mortality

ratio

Industry Variance Total deaths X2

2

1

 Indicates the probability of obtaining these results due to

chance is less than .001.

2 Nonclassifiable includes establishments which cannot be

classified in any other industry.

1

 Hypoxia is a deficiency in the amount of oxygen reaching body tissue.

For additional information, see M. Sittig, Handbook of Toxic and Hazardous Chemicals, Noyes Publications, New Jersey, 1981, p. 137. 2

 NIOSH Alert: Preventing Carbon Monoxide Poisoning from Small

Gasoline-powered Engines and Tools, National Institute of Occupational

Safety and Health, Publication No. 96-118, 1996, p. 3. 3

 “Code of Federal Regulations, 1910.1000,” Occupational Safety and

Health Administration, Washington, DC, U.S. Government Printing Office,

1997. 4

 S. M. Silvers and N. B. Hampson, “Carbon Monoxide Poisoning Among

Recreational Boaters,” Journal of the American Medical Association, Vol.

274, 1994, pp. 1614-16. 5

 See Netzel R. A. Cobb, “Unintentional Carbon Monoxide-related Deaths

in the United States, 1979-1988,” Journal of the American Medical Association, Vol. 226, 1991, pp. 659-663. 6

 NIOSH Alert: Preventing Carbon Monoxide Poisoning, p. 5. 7

 “Deaths from Motor-vehicle-related Unintentional Carbon Monoxide

Poisoning—Colorado, 1996, New Mexico, 1980-1995, and United States,

1979-1992,” Morbidity and Mortality Weekly Report, Vol. 45, 1996, pp.

1029-32. 8

 Center for Disease Control, “Carbon Monoxide Poisoning from use of

Gasoline-fuel Power Washers in an Underground Parking Garage—District

of Columbia, 1994,” Morbidity and Mortality Weekly Report, Vol. 44, May

12, 1995, pp. 356-64. 9

 Data on fatal work injuries are from the Bureau of Labor Statistics’

Census of Fatal Occupational Injuries (CFOI), 1992-96. 10 Industry is classified according to the Standard Industrial Classification Manual 1987. 11 D. Spiegelman, J. D. Wang, and D. Wegman, “Epidemiologic Programs

for Computers and Calculators,” American Journal of Epidemiology, Vol.

118, October 1983, pp. 599-607. 12 N. Mantel and W. Haenszel, “Statistical Aspects of the Analysis of Data

from Retrospective Studies of Disease,” Journal of the National Cancer Institute, Vol. 22, April 1959, pp. 719-48.

TABLE 2. Proportionate mortality ratios for carbon monoxide poisoning fatalities by industry, 1992-96