Chronic obstructive pulmonary disease (COPD) is a leading cause of morbidity and mortality
worldwide. Tobacco smoking is established as a major risk factor, but emerging evidence
suggests that other risk factors are important, especially in developing countries.
An estimated 25-45% of patients with COPD have never smoked; the burden of non-smoking
COPD is therefore much higher than previously believed. About 3 billion people, half
the worldwide population, are exposed to smoke from biomass fuel compared with 1.01
billion people who smoke tobacco, which suggests that exposure to biomass smoke might
be the biggest risk factor for COPD globally. We review the evidence for the association
of COPD with biomass fuel, occupational exposure to dusts and gases, history of pulmonary
tuberculosis, chronic asthma, respiratory-tract infections during childhood, outdoor
air pollution, and poor socioeconomic status.