A case-control study of
lung cancer involving interviews with 965 female patients and 959 controls in Shenyang and Harbin, two industrial cities which have among the highest rates of
lung cancer in China, revealed that cigarette smoking is the main causal factor and accounted for about 35% of the tumours among women. Although the amount smoked was low (the cases averaged eight cigarettes per day), the percentage of smokers among women over age 50 in these cities was nearly double the national average. Air pollution from
coal burning stoves was implicated, as risks of
lung cancer increased in proportion to years of exposure to 'Kang' and other heating devices indigenous to the region. In addition, the number of meals cooked by deep frying and the frequency of smokiness during cooking were associated with risk of
lung cancer. More cases than controls reported workplace exposures to
coal dust and to
smoke from burning fuel. Elevated risks were observed for smelter workers and decreased risks for textile workers. Prior
chronic bronchitis/
emphysema,
pneumonia, and recent
tuberculosis contributed significantly to
lung cancer risk, as did a history of
tuberculosis and
lung cancer in family members. Higher intake of
carotene-rich vegetables was not protective against
lung cancer in this population. The findings were qualitatively similar across the major cell types of
lung cancer, except that the associations with smoking and previous
lung diseases were stronger for squamous/oat cell
cancers than for
adenocarcinoma of the lung.