Exposure to passive smoking is linked to increased prevalence of chronic obstructive pulmonary disease (COPD) and this association could cause 1.9 million deaths among non-smokers in China, according to a study published in this week's edition of The Lancet.

It is the largest study ever in China showing a strong relationship between passive smoking and COPD, a lung disease in which the lungs are damaged making it hard to breathe.

Dr Peyman Adab and Professor K K Cheng, University of Birmingham, the United Kingdom, and colleagues from the Hong Kong School of Public Health and Guangzhou 12th Hospital used data from the Guangzhou Biobank Cohort Study to do their research. A total of 15,379 non-smokers aged over 50 were included in this analysis.

The researchers found that people exposed to high levels of passive smoking, equivalent to 40 hours a week for more than five years, were on average 48 percent more likely to develop COPD.

There were also significant associations between reported respiratory symptoms and increasing passive smoking exposure, generally a 16 percentage increased risk for any respiratory symptom.

The authors conclude: "If our risk estimates are correct, and assuming that current mortality and passive smoking exposure patterns continue, of the 240 million people aged over 50 alive today in China, high exposure to passive smoking would result in about 1.9 million excess deaths from COPD among those who have never smoked."

The prevalence of COPD ranged from 0.23 percent to 18.3 percent worldwide. A recent large epidemiological survey estimated the prevalence of COPD in China was 8.2 percent.

Figures from the Ministry of Health show that China has an estimated 350 million smokers, almost a third of the world's 1.1 billion smokers. According to Cheng, in China smoking is a major risk factor for COPD, and also the proportion of non-smokers who develop COPD is much higher than in most other countries.

Though passive smoking poses a smaller risk compared to active smoking, the impact is quite considerable. According to a study published in the 2005 Chinese Journal of Epidemiology, more than 460 million Chinese are regularly exposed to second-hand smoking, the majority being women and children.

Generally, most women are non-smokers and they are exposed to high levels of passive smoking at home, at work and other public places.

"This is a big public health problem as 100,000 people died due to passive smoking each year in China, with COPD contributing about half of them," says Cheng.

Except for smoking and passive smoking, occupational exposure, some genetic variants and indoor air pollution from biomass combustion may contribute to COPD.

"Not smoking is the main way to prevent COPD. Many lives of non-smokers could be saved if they are not exposed to passive smoking," suggests Cheng.

Due to relaxed smoking laws and a strong smoking culture, few restrictions exist to forbid passive smoking in many public places in China.

The upcoming Olympics is regarded as a good opportunity to promote smoking ban in public places. All Olympic stadiums, the Olympic village and all restaurants with The Beijing Organizing Committee for the Games of the XXIX Olympiad (BOCOG) contracts will be smoke-free zones.

It is also estimated that by the end of the year Ministry of Health will complete the revision on Regulations on Hygienic Management in Public Places, which will supposedly support a smoking ban in public places.

(China Daily September 5, 2007)