Air pollution and lung cancer in Trieste, Italy: Spatial analysis of risk as a function of distance from sources

To investigate the relationship between four sources of environmental pollution (shipyard, iron foundry, incinerator, and city center) and lung cancer risk, we conducted a case-control study of deceased men in Trieste, Italy. We identified 755 cases of lung cancer and 755 controls through the local autopsy registry. Information on smoking habits, occupational history, and place of residence were obtained from the subjects' next of kin. The case-control design was used to properly account for subject-specific confounders, which represent a major problem in geographical analysis. Spatial models were used to evaluate the effect of sources of pollution on lung cancer after adjustment for age, smoking habits, likelihood of exposure to occupational carcinogens, and levels of air particulate. The models are based on distance from the sources and enable estimation of the risk gradient and directional effects separately for each source. The risk of lung cancer was highly related to the city center (p = 0.0243), with an excess relative risk at zero distance of 2.2 and a smooth decrease moving away from the source (-0.015), and related to the incinerator (p = 0.0098), with an excess relative risk of 6.7 in the source and a very steep decrease (-0.176). These results are consistent with findings of previous analyses and provide further evidence that air pollution is a moderate risk factor of lung cancer.