causes of copd

Smoking

The primary risk factor for COPD is chronic tobacco smoking. In the United States, 80 to 90% of cases of COPD are due to smoking.^[9] Exposure to cigarette smoke is measured in pack-years, the average number of packages of cigarettes smoked daily multiplied by the number of years of smoking. Not all smokers will develop COPD, but continuous smokers have at least a 25% risk after 25 years.^[10] The likelihood of developing COPD increases with increasing age as the cumulative smoke exposure increases. Inhaling the smoke from other peoples' cigarettes (passive smoking) can lead to impaired lung growth and could be a cause of COPD. It should be noted that, although tobacco smoking is the most common cause of COPD, the inhalation or smoking of other substances or drugs, for example cannabis, are also linked to the development of COPD.

Intense and prolonged exposure to workplace dusts found in coal mining, gold mining, and the cotton textile industry and chemicals such as cadmium, isocyanates, and fumes from welding have been implicated in the development of airflow obstruction, even in nonsmokers^[11]. Workers who smoke and are exposed to these particles and gases are even more likely to develop COPD. Intense Silica dust exposure causes silicosis, a restrictive lung disease distinct from COPD however less intense silica dust exposures have been linked to a COPD-like condition^[12]. The effect of occupational pollutants on the lungs appears to be substantially less important than the effect of cigarette smoking^[13].