Appendix II - Summaries Of and Data From Articles On Poisonings From Vehicle-Generated Carbon Monoxide

    The thrust of the research effort behind this report was to gather data, from whatever source, on selected non-traffic motor vehicle related safety hazards. The sources reviewed included academic research articles. The basic findings of the articles reviewed are presented in the body of this report. A brief summary of each article reviewed and selected data from each article is presented here.

Mott JA, Wolfe MI, Alverson CJ, Macdonald SC, Bailey CR, Ball LB, Moorman JE, Somers JH, Mannino DM, Redd SC. National vehicle emissions policies and practices and declining US carbon monoxide-related mortality. JAMA 2002;Aug 28;288(8):988-95.
    This comprehensive study examined 31 years (1968-1998) of national mortality and motor vehicle emissions data. The study describes the reductions in overall carbon monoxide related deaths during this period and particularly the reductions in motor vehicle-related carbon monoxide deaths. While rates of reduction varied during portions of the 31-year period studied, overall unintentional motor vehicle-related carbon monoxide death rates declined from 20.2 deaths to 8.8 deaths per 1 million person-years, or about 57.8 percent. After 1975, the year in which catalytic converters were introduced into automobiles, the authors found a reduction in vehicle-related carbon monoxide deaths of 76.3 percent, a decline from 4.0 to 0.9 deaths per 1 million person-years. While not drawing any hard and fast conclusions, the authors nonetheless felt compelled to comment on this saying, “the concurrent decline in motor vehicle-related emissions and poisoning deaths that only occurred following the first national intervention to reduce CO in automobile exhaust appears unlikely to be coincidental.”
    Two areas of data presented in this article are of particular value to the non-traffic research in this report. First, there were 238 unintentional motor vehicle-related deaths from carbon monoxide in 1998,, which is consistent with both other articles summarized below and the death certificate research conducted for this report. It adds to the certainty as to the magnitude and scope of the problem. Second, the data presented in the study (see table below) indicate that vehicle-related carbon monoxide deaths primarily affect adults, which is again consistent with information derived from death certificate research and other sources.

Table XV: (from Mott JA, et.al.) 1998 CDR (crude death rate) per 1 Million Person-years (No. of Deaths)

Shelef M. Unanticipated benefits of automotive emission control: reduction in fatalities by motor vehicle exhaust gas. Sci Total Environ 1994 May 23;146-147:93-101.
    This article is simply noted here because it also documents what is more completely described in the article cited above.

Fatalities Associated With Carbon Monoxide Poisoning From Motor Vehicles, 1995-1997. Research Note, April 2000, National Highway Traffic Safety Administration.
    Figures presented in this note are consistent with the article by Mott et. al. and the death certificate research conducted in support of this report. Of particular note is the fact that this note identified a consistent annual number of vehicle-related carbon monoxide deaths in moving vehicles, something that the researchers involved in this report did not find, although one such incident was located. Also, the note presented data that support the notion that carbon monoxide poisonings from motor vehicle exhaust are more likely to occur in the cooler months. Data from this article relevant to the research on which this report is based appear in the following tables.

Table XVI: (from NHTSA Research Note) Vehicle-Related Deaths Associated With CO Poisoning: 1995-1997*

*Suicides were intentionally left out of this chart. Percentages are based on totals that include suicides.

Table XVII: (from NHTSA Research Note) Accidental CO Fatalities with Stationary Vehicles by
Vehicle Location: 1995-1997

Table XVIII: (from NHTSA Research Note) All Accidental Vehicle-Related CO Fatalities in 1995-1997
by Season of Occurrence

Marr LC, Morrison GC, Nazaroff WW, Harley RA. Reducing the risk of accidental death due to vehicle-related carbon monoxide poisoning. J Air Waste Manag Assoc 1998 Oct;48(10):899-906.
    Rather than focus on the numbers of incidents of carbon monoxide poisoning, this paper sets out measures of the risk of carbon monoxide poisoning in the typical settings in which most of the carbon monoxide poisonings continue to occur. Using various data sources and methods of statistical analysis, the authors came up with the relative risk of death in a number of situations. That is reflected in the table below.

Table XIX: (from Marc LC et. al.) Risk of Death for Four Accidental Poisoning Scenarios With All vehicles and
With Pre-1975 Vehicles Removed

*A range in the risk of death in garages is presented because of uncertainty in garage air-exchange rates.

    The garage size assumed in determining the risk factors above is 90 m3. Changes in the size of the garage would affect the risks of carbon monoxide poisoning, the authors note. They also cite a number of other factors that would affect the risks involved. These include:

    Another factor that could confound the authors’ results is “the distribution of garaged vehicles versus vehicle age.” “This study has assumed that all vehicles tested in the random roadside emissions inspection are equally likely to be parked in an enclosed garage, but it is possible that a higher fraction of newer vehicles are kept in garages because of socioeconomic factors. It this were true, then the risk of death from CO poisoning has been overestimated because the older vehicles, which are responsible for a disproportionately high fraction of deaths, would be less likely to be parked in enclosed garages.”
    What is interesting about the risk factors presented in this paper is that they are based on what is fairly prolonged exposure to the exhaust from an operating vehicle. As indicated earlier in this report, there have been significant declines in deaths from vehicle-generated carbon monoxide over the past 30 years. Also, the current numbers of vehicle-generated carbon monoxide deaths is quite small. With the addition of the risk factors developed by this paper, a picture emerges, which is consistent with information derived from other sources and provided in this report, that suggests that in the majority of cases of accidental carbon monoxide poisonings from vehicle exhaust, factors beyond the vehicle itself play a major role. These factors may include alcohol abuse or serious errors or lapses in judgment on the part of the victim, such as simply forgetting to turn off an operating vehicle in a garage that is attached to a home.

Girman JR, Chang YL, Hayward SG, Liu KS. Causes of unintentional deaths from carbon monoxide poisonings in California. West J Med 1998 Mar;168(3):158-65.
    Based on unintentional vehicle-related carbon monoxide deaths in California over a 10-year period (1979 to 1988), this study supports certain characteristics of these types of deaths. Among the article’s findings:

Death from motor-vehicle-related unintentional carbon monoxide poisoning – Colorado, 1996, New Mexico, 1980-1985, and United States, 1979-1992. MMWR Morb Mortal Wkly Rep 1996 Nov 29;45(47):1029-32.
    As with the articles reported on above, this article provides further supporting information relating to the circumstances most frequently involved in vehicle-generated carbon monoxide poisonings. Among the findings of this article are:

Yoon SS, Macdonald SC, Parrish RG. Deaths from unintentional carbon monoxide poisoning and potential prevention with carbon monoxide detectors. JAMA 1998 Mar 4;279(9):685-7.
    This study, which basically advocates more extensive use of carbon monoxide detectors, includes findings similar to those found in the paper by Girman, et. al. Alcohol levels of greater than 0.01 percent were found in 53 percent of those identified in the study as having died from motor vehicle-related carbon monoxide. (The study examined a total of 136 deaths from CO poisoning that were investigated by the New Mexico Office of the Medical Investigator, 1980 through 1995.)

Rao R, Touger M, Gennis P, Tyrrell J, Roche J, Gallagher EJ. Epidemic of accidental carbon monoxide poisonings caused by snow-obstructed exhaust systems. Ann Emerg Med 1997 Apr;29(4):561.
    Snow obstructed exhaust systems represent special circumstances that substantially increase the risk of carbon monoxide poisoning from vehicle-generated carbon monoxide. This article reports on the spike in carbon monoxide poisonings that resulted when on January 8, 1996, the New York City metropolitan area was blanketed by more than 24 inches of snow. The article focuses on 25 cases of carbon monoxide poisoning, 18 during the first 24 hours following the snowfall, that were referred to a medical center in New York for hyperbaric oxygen treatment to offset the effects of the patients having been exposed to CO in a stationary automobile with the engine running and the exhaust system obstructed by snow. Usually the patients involved were attempting to keep warm. There was one death from CO in the city that was not included in the study. Twenty (20) of the 25 patients included in the study arrived unconscious at the emergency department.

Baron RC, Backer RC, Sopher IM. Unintentional deaths from carbon monoxide in motor vehicle exhaust: West Virginia. Am J Public Health 1989 Mar;79(3):328-30.
    This article again supports several tendencies inherent in motor vehicle-related carbon monoxide deaths:

Hampson NB, Norkool DM. Carbon monoxide poisoning in children riding in the back of pickup trucks. JAMA 1992 Jan 22-29;267(4):538-40.
    This study identified circumstances that represent a particular risk of carbon monoxide poisoning in children. The authors examined, through follow up telephone interviews, 68 patients treated with hyperbaric oxygen for accidental carbon monoxide poisoning between 1986 and 1991. These patients were treated at a private, urban, tertiary care center in Seattle, WA and ranged from 4 to 16 years old. Twenty (20) of these cases occurred as a result of the children riding in the back of pickup trucks. In 17 of these, the children were riding under a rigid closed canopy on the rear of the truck. In three cases the children rode beneath a tarpaulin. Fifteen (15) of the children who had been riding in pickups had lost consciousness. One died, one had permanent neurologic deficits, and 18 had no recognizable after effects of the carbon monoxide poisoning. In all 20 cases, the truck exhaust system had a previously known leak or tail pipe that exited at the rear rather than at the side of the pickup truck.