Carbon Monoxide Poisoning as a New Method of Suicide in Hong Kong

It is well known that individuals in different countries tend to use different methods for committing suicide (1). Jumping from a building has been the most prevalent method in Hong Kong, where 95 percent of the population lives in high-rises, followed by hanging. These two methods accounted for about 50 percent and 30 percent, respectively, of the 3,917 suicides that occurred in Hong Kong between 1995 and 1999 (2).

Before 1997, carbon monoxide poisoning accounted for less than 2 percent of all suicide cases in Hong Kong. Domestic gas, which has not been detoxified in Hong Kong, was the most common source of carbon monoxide. Suicide by using car exhaust was also uncommon, with only three cases reported in 1998. A MEDLINE search uncovered no reports of intentional carbon monoxide poisoning by charcoal burning.

Such a case occurred in Hong Kong in November 1998. The incident made front-page news and was extensively covered by the media. We investigated the incidence of such suicides both before and after the publicized case.

Methods

We searched for the keywords "suicide," "carbon monoxide poisoning," and "burning charcoal" in the Hong Kong NewsBots—an Internet database of six major newspapers—for a two-year period, from January 1, 1998, to December 31, 1999. We supplemented this with a manual search of newspaper clippings. The collected data were checked against a list from the government's birth and death registry on suicide by carbon monoxide poisoning, excluding cases in which domestic gas was used. The sex and age of the victims, the details of the suicide scene, and the methods of suicide were noted on the database forms.

Results

Between January 1998 and December 1999, a total of 1,750 suicides were reported in Hong Kong—886 by jumping and 533 by hanging. Fifty-six suicides by charcoal burning—including five suicide pacts involving nine people—were reported during the same period. No suicides of this type were reported between January 1998 and November 23, 1998, when a case was reported in the media. Twenty-two of the 56 cases (39 percent) occurred in the nine weeks after the first reported incident. Over the following months, the number of cases fluctuated between zero and four, but rose to seven in December 1999, the last month of the study period (Figure 1).

The mean±SD age of the victims was 39±9.3 years (range=19 to 62 years); 36 (64 percent) were men. Individuals who committed suicide by charcoal burning were younger on average than those who used the more common methods of jumping (47± 20 years) and hanging (55±19 years) (t=-6.2 and -11.7, df=79 and 92, respectively, p<.001). Sex differences among the three groups were not significant.

Almost 90 percent of the charcoal burning suicides occurred in the victims' homes in Hong Kong. Evidence suggesting the use of alcohol or hypnotic agents was found in 11 of the cases (20 percent). Suicide notes were found in 33 of the cases (59 percent). All of the victims used barbecue charcoal to produce the carbon monoxide.

Discussion and conclusions

The influence of the media on suicide rates among young people has been well studied, and visual imagery in the media has been shown to be a powerful tool for imitative suicide (3). The victim of the first reported case in Hong Kong of suicide using charcoal burning reportedly learned of the method from a Japanese film. Before the extensive media coverage of the first case, this method was unheard of in Hong Kong. Similar suicides in the months following the highly publicized case may have been due to the copycat effect, with the number of cases leveling off as the effect diminished. As winter approached, the number of incidents again rose.

Carbon monoxide poisoning by charcoal burning is a relatively simple method of committing suicide, and it is especially suited to the local culture. Poisoning with car exhaust requires both a car and a garage or a remote area, which are scarce in Hong Kong. The odor of domestic gas is easily detectable in the densely populated housing units, and the risk of an explosion that could harm others probably deters people from using it as a suicide method. In interviews with the authors, some survivors who had attempted suicide by charcoal burning indicated that they chose this method because it was easy and painless. Many had used alcohol or hypnotic drugs during the attempt, so they felt no discomfort at all.

Cultural attitudes toward death may influence the choice of method of suicide (4). Traditional Chinese belief emphasizes preservation of the complete corpse for burial, which ensures a good beginning for the next incarnation. Therefore, carbon monoxide poisoning inside a quiet room may be preferable to the physical trauma caused by jumping from a tall building. In four of the cases we studied, a traditional religious basin for worshipping ancestors was used to hold the burning charcoal, perhaps in the hope of smoothing the transition of the soul to the next world.

Long-term studies are needed to determine whether charcoal burning is replacing other forms of suicide or whether it is contributing to a rise in the overall suicide rate in Hong Kong.

The authors are associated with the department of psychiatry at the Chinese University of Hong Kong, 11/F, Prince of Wales Hospital, Shatin, N.T., Hong Kong, SAR, China (e-mail, chungwsd@ netvigator.com).