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Unintentional Deaths from Carbon Monoxide Poisoning -- Michigan, 1987-1989

Deaths from unintentional carbon monoxide (CO) poisoning in the United States result primarily from exposure to motor-vehicle exhaust and occur more often during the cold months of the year and in northern and midwestern states (1-3). In Michigan, from 1987 through 1989, 103 deaths were related to unintentional CO poisoning. To identify approaches for prevention of unintentional CO poisoning in Michigan, the Michigan Council on Injury Control (MCIC) studied death records and medical examiner (ME) records to determine the manner of deaths related to unintentional CO poisoning in that state from 1987 through 1989. This report summarizes findings of the investigation.

MCIC used the Michigan Department of Public Health's statewide death registry to identify all death records from 1987 through 1989 with underlying cause of death listed as International Classification of Diseases, Ninth Revision (ICD-9) E codes 868.0- 868.9 (CO or other utility gas). MCIC then selected as cases Michigan residents who died in the state during 1987-1989 and whose cause of death was recorded as unintentional (i.e., not suicide or homicide). Deaths involving fires were excluded.

A total of 121 deaths attributable to unintentional poisoning by CO or other utility gas were identified; records for each case were then requested from the county MEs. Of these, 22 were excluded, including nine that were associated with fires or miscoded, eight that were identified by the ME as suicide, and four that occurred outside Michigan; for one case, no death record was found. Four additional deaths that fit the case definition but that did not appear on the original case list were identified; two of the four cases involved couples of whom only one of the pair appeared on the original list, and the remaining two cases were identified during a manual review of ME records from a large urban county.

Of the 103 deaths that were both unintentional (determined by review of the case report) and involved CO poisoning, 83 (81%) were among males. Exposure to motor-vehicle exhaust caused 69 (67%) deaths, and 34 (33%) were attributed to home-heating devices or other sources.

Motor-vehicle-related deaths occurred most often among persons aged 25-44 years (4.3 per million population compared with 2.4 per million for all ages) and from September through April (78%) (Figure 1). Of the deaths attributed to motor-vehicle exhaust, 64% occurred in a closed garage; of the 49 persons tested for blood alcohol concentration (BAC), 35 (71%) had a BAC of greater than or equal to 0.01 g/dL (Table 1). Of the 42 persons who were tested for drugs, five (12%) were positive. Of the deaths not related to motor vehicles, the rate was highest for persons aged greater than or equal to 65 years (2.7 per million population compared with 1.1 per million for all ages); 87% of these deaths occurred during November-March.

Reported by: MA Gregor, MHA, Michigan Council on Injury Control, Grand Rapids; G Van Amburg, MPH, Office of the State Registrar; JC Thrush, MPH, Injury Research and Control Section, KR Wilcox, Jr, MD, State Epidemiologist, Michigan Dept of Public Health. Air Pollution and Respiratory Health Br, Div of Environmental Hazards and Health Effects, National Center for Environmental Health, CDC.

Editorial Note

Editorial Note: In the United States, deaths attributed to unintentional CO poisoning decreased from 1979 through 1988 by approximately 63 deaths per year (from 1513 to 878) (4). However, because CO is colorless, odorless, and nonirritating, its presence is not easily detected and remains a substantial health risk. Early symptoms of exposure include headache, dizziness, weakness, nausea, visual disturbances, and confusion; with prolonged exposure, coma and death may result (4-6).

The findings in this study underscore the seasonal patterns in unintentional CO-related deaths and the predominance of deaths related to exposure to motor-vehicle exhaust (1-3). In Michigan, most of these motor-vehicle-related deaths occurred in a closed garage, suggesting that many persons may not be aware of the danger of CO exposure. In addition, the findings indicate an increased risk for motor-vehicle-related deaths for young persons and an increased rate of death from other CO sources (e.g., faulty home-heating systems) for older persons.

Public health measures to prevent death from unintentional CO poisoning have included improvements in home-heating appliances and their installation and maintenance, stricter occupational exposure standards, improvements in ventilation in new buildings, prevention education, and improvements in treatment for acute poisoning such as the use of hyperbaric oxygen. Further educational efforts should be directed toward young drivers, particularly males, and toward the elderly or others living in homes with possibly obstructed chimneys and old heating systems, including homes that use butane and kerosene space heaters, wood stoves, and charcoal grills. In addition, the relation between alcohol consumption and risk for CO poisoning, especially motor-vehicle-related risk, should be emphasized in driver's education courses and other programs.

Recent advances in technology have improved the effectiveness of CO detection devices in preventing unintentional CO poisoning. Older CO detection devices measured only CO concentration; however, newer CO detection devices are able to measure cumulative CO exposure, which is a more useful measure of health risk. Underwriters Laboratories has recently implemented a standard (UL 2034) for certifying CO detectors for home use (7).


  1. Cobb N, Etzel R. Unintentional carbon monoxide-related deaths in the United States, 1979-1988. JAMA 1991;266:659-63.

  2. Baron RC, Backer RC, Sopher IM. Unintentional deaths from carbon monoxide in motor vehicle exhaust: West Virginia. Am J Public Health 1989;79:328-30.

  3. Baron RC, Backer RC, Sopher IM. Fatal unintended carbon monoxide poisoning in West Virginia from nonvehicular sources. Am J Public Health 1989;79:1656-8.

  4. Thom SR, Keim LW. Carbon monoxide poisoning: a review. Clinical Toxicology 1989;27:141-56.

  5. CDC. Carbon monoxide levels in indoor tractor-pull events -- Manitoba, Canada. MMWR 1990;39:743-5.

  6. Meredith T, Vale A. Carbon monoxide poisoning. Br Med J 1988;296:77-8.

  7. Underwriters Laboratories. UL 2034: Standard for single and multiple station carbon monoxide detectors. 1st ed. Northbrook, Illinois: Underwriters Laboratories, Inc, April 30, 1992.

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