In western countries chronic obstructive pulmonary disease is seen as predominantly a disease of smokers - and the only way to halt its progression is to stop smoking.
In China however, thousands of non-smokers shows signs of non-reversible airways obstruction - and the reasons seem to be the country's ubiquitous use of dirty coal for cooking and heating. A study of 300,000 Chinese adults who have never smoked has found that one in twenty (5%) have COPD, with the condition more common in women than in men.
The main factors associated with COPD were low income, lack of education, living in a rural area and a prior history of tuberculosis. However, another major factor was cooking with coal.
The study researchers, from the Chinese Academy of Medical Sciences, Beijing, and Oxford university, said the link between low income and lung disease might be due to higher exposure to infections and to air pollution.
The findings are published in the European Respiratory Journal.