Researchers from several Danish universities claim that long-term exposure to traffic-related air pollution is linked to the development of chronic obstructive pulmonary disease (COPD). Zorana J. Andersen, et al., “Chronic Obstructive Pulmonary Disease and Long-Term Exposure to Traffic-Related Air Pollution: A Cohort Study,” Am. J. Respir. Critc. Care Med. (2010). In a national cohort study, researchers followed 57,053 Danes, ages 50 to 64, from 1993 to 2006. They assessed the association between exposure to air pollution and COPD incidence for the full cohort and for participants with and without health conditions, including asthma, diabetes or cardiovascular disease. They also estimated the levels of nitrogen dioxides and nitrogen oxides at the participants’ homes beginning in 1971.

The researchers concluded that 25 to 35 years of exposure to high levels of nitrogen-based air pollution created by traffic was a significant risk factor for COPD. The impact of air pollution was greater in those who had asthma and diabetes, according to the study.