Exposure to burning solid fuel indoors for heat and cooking may cause the lung ailment known as chronic obstructive pulmonary disease, a study of more than 20,000 people in China has shown.

The finding, published in the European Respiratory Journal, is significant because COPD has long been associated with smoking and little research has been done to find out why non-smokers also suffer from the disease.

COPD includes chronic bronchitis and emphysema.

Emphysema is the loss of elasticity of lung tissues, resulting in the collapse of small airways and leading to shortness of breath and hyperventilation.

The study covered 20,245 people over 40 years of age in seven Chinese provinces who were interviewed about their smoking habits, family health history and exposure to smoke from solid fuels, such as wood, coal and dung.

Among the participants, 12,471 were non-smokers and 5.2 percent of them were diagnosed as suffering from COPD, wrote the researchers, led by Ran Pixin at the State Key Laboratory of Respiratory Disease in southern China's Guangzhou City.

The prevalence of COPD among non-smokers varies widely between countries: 6 percent in Mexico City, 9 percent in the United States and 16 percent in Santiago de Chile. These statistics suggest the illness may be linked to other causes such as differences in lifestyle, behavior and exposure to various toxic substances.

After adjusting for other possible causes, including passive smoking, the Chinese researchers found that exposure to various types of smoke in the home, such as that produced by burning coal and biomass, was the leading cause of COPD in non-smokers.

About 73 percent had been exposed for at least a year to burning fuel indoors for the purpose of heating or cooking.

In four out of 10 cases, kitchen ventilation was poor and both men and women were harmed, they added.

Nearly four-fifths of the non-smokers, or 78 percent, were also found to have lived with tobacco fumes.

It is well known that children of smoking parents are more likely to suffer from respiratory disease as adults and the researchers said the problem will be more acute in China, where nearly 40 percent of adults smoke.

"Our results can probably be applied to other developing countries, such as India and Nepal, which have a similar indoor pollution problem", wrote the researchers.

They hoped a substantial number of COPD cases could be avoided through health education, better ventilation in kitchens and getting people to quit smoking.

(Shanghai Daily February 21, 2009)