High pollution may increase SARS death rate

Air pollution is associated with an increased risk of dying from SARS, according to a report published this week in Environmental Health: A Global Access Science Source. The study shows that patients with SARS are more than twice as likely to die from the disease if they come from areas of high pollution.

5,327 cases of SARS have been diagnosed in mainland China since November 2002 and so far 349 patients have died from their disease. SARS death rates vary between regions of China, with higher rates in the north of the country. A team of researchers from the University of California in Los Angeles, the Jiangsu Provincial Center for Disease control and Prevention, and Fudan University School of Public Health investigated whether these differences could be explained by differences in air pollution levels.

Using publicly available SARS data, the researchers assessed the death rates of patients with SARS in five different regions of China. They used data published by the Chinese National Environmental Protection Agency, to assess the air pollution levels in these different regions between April and May 2003. These dates coincide with the time when the majority of SARS cases were diagnosed.

Data analysis revealed a strong positive correlation between air pollution and SARS fatality. The researchers write: “Our studies demonstrated a positive association between levels of air pollution and SARS case fatality in the Chinese population.”

The researchers categorised the regions according to their level of air pollution. Guangdong, with an air pollution index of 75, was said to have a low level of pollution, Tianjin, with an air pollution index of over 100, a high level of pollution and Shanxi, Hebei and Beijing, moderate pollution levels.

Mortality rates of patients with SARS increased as pollution levels increased. In regions with low air pollution, the death rate was 4.08%, whereas in areas with moderate or high air pollution levels, the death rates were 7.49% and 8.9%, respectively.

The authors suggest that, “long-term or short-term exposure to certain air pollutants could compromise lung function, therefore increasing SARS fatality.”

The researchers acknowledge that their study is limited. They were not able to take into account the socioeconomic status or the smoking habits of the SARS patients, nor did they consider the treatment that the patients were given. All of these may have contributed to the patients’ outcome.

However, the two regions with the highest case fatality rates were Beijing and Tianjin. The researchers suspect that patients would probably have received better clinical support in these areas. If this is the case, then air pollution may play an even greater role in increasing death rates than their data suggests.