Much has been written about the short term effects of air pollution on health but relatively little about possible long term effects such as lung cancer. Now data from Norway have suggested a link between lung cancer and air pollution.

A population based study of cardiovascular disease included 16 209 Oslo men aged 40–49 in 1972–73. Data from this study were linked to data from Norwegian national cancer and death registries. Data from the Norwegian Institute for Air Research were used to estimate air pollution levels (sulphur dioxide and nitrogen oxides) at the home address of each subject each year for 1974–98. During the period of follow up 2892 men (17.9%) developed cancer and 422 (2.6%) developed lung cancer (1.19/1000 men/year). Between 1973 and 1995 estimated sulphur dioxide concentrations tended to fall and estimated nitrogen oxide concentrations tended to rise. After adjusting for age, smoking, and education there was an 8% increase in lung cancer risk for each 10 μg/m³ increase in average home address nitrogen oxide concentration between 1974 and 1978 (risk ratio 1.08, 95% confidence interval 1.02 to 1.15). For the same increase in sulphur dioxide the corresponding risk ratio was 1.01(0.94 to 1.08). Average five year (1974–78) exposure to nitrogen oxides at a level of 30 μg/m³ or greater increased the risk of lung cancer by 37% (crude risk ratio 1.37) compared with an average level of less than 10 μg/m³.

Increased home address exposure to nitrogen oxides is associated with increased risk of lung cancer. Compared with smoking urban air pollution is a weak risk factor for lung cancer.