Longitudinal relationships between lung cancer mortality rates, smoking, and ambient air quality: a comprehensive review and analysis

Abstract

Lung cancer mortality (LCM) has been associated with smoking and air pollution. This article draws on smoking relationships to clarify air pollution relationships. We analyzed cohort and population-based smoking studies and identified effects of latency and cumulative exposures. We found cogent relationships through longitudinal rather than cross-sectional analysis, thus involving historical data. We also considered passive smoking, occupational exposures, radon, and established carcinogens. We found stable nonsmoking LCM rates during periods of improving ambient air quality. We considered 59 crosssectional studies of lung cancer and air pollution and found similar statistically significant relative risks for PM 2.5 , PM 10 , EC, NO 2 , SO 2 , SO 2À 4 , and O 3 , and minimal risks for benzo(alpha)pyrene and trace metals. Most air pollution studies did not consider latency, exposure duration, or temporal trends; none included estimates of smoking risks implied by their models. We conclude that while LCM studies of smoking, radon, and occupational exposures appropriately considered latency and cumulative exposures; ambient air quality studies have not. Lung cancer has a long memory and exposure histories are required. Effects of cumulative exposures after pollution abatement include substantially reduced risk estimates, delayed health benefits, inability to show accountability for the abatement. However, associations of lung cancer with ambient air pollution cannot be ruled out, especially for historic periods when much higher exposures persisted. Given the major reductions in air quality and smoking habits that have been realized since the Clean Air Act, new studies of LCM and air pollution, including smoking histories and exposure data decades before diagnosis, are needed. HIGHLIGHTSLifetime cigarette consumption is a good predictor of lung cancer risk. The latent period for lung cancer ranges from about 10 to 30 y. Lung cancer risks for nonsmokers have been stable during the period when ambient air quality improved substantially. Risks of established airborne carcinogens may have been important in the past but not under current conditions. Radon can be important. Air pollution-lung cancer risks should be evaluated jointly with smoking risks but are sensitive to their accuracy. When cumulative exposures to conventional air pollutants are considered rather than concurrent, the applicable risk estimates may decrease by an order of magnitude and abatement benefits will not be readily apparent. Most of the recent cross-sectional studies of lung cancer and regulated air pollutants did not consider latency, duration of exposure, or established carcinogens and their findings have been misinterpreted. Effects of smoking on LCM are now well established as are the spatial distributions of ambient air pollution; however, linkages among the three parameters remain uncertain.

From kidney injury to kidney cancer

“…1 Tissue injury is a known trigger of cancerogenesis for 2 reasons: (i) its potential to induce DNA damage and somatic mutations, especially in tissue-resident long-lived stem cells 2 ; and (ii) its potential to promote the expansion of such mutated cells during the process of tissue repair. 3 For example, these 2 mechanisms contribute to inflammatory bowel disease-related colorectal cancer 4 and to lung cancer related to exposures to toxic smokes and dust particulates, 5 atrophic gastritis-related gastric cancer, 6 and cirrhosis-related hepatocellular carcinoma. 7 Numerous epidemiologic studies report the association between chronic kidney disease (CKD) and kidney cancer (Table 1 [8][9][10][11][12][13][14][15] ).…”

Incidence trends in bladder and lung cancers between Denmark, Finland and Sweden may implicate oral tobacco (snuff/snus) as a possible risk factor

“…Because of the low level of smoking among Swedish men, it is evident that the population attributable fraction of smoking for bladder cancer is declining, and other factors may exert a detectable role. Considering the lag time between smoking and bladder cancer of 20 to 40 years, smoking related bladder cancer should still be declining in Swedish men [ 3 , 4 ]. Thus, new factor(s) appear to counteract this decline.…”

“…The incidence trends of lung and urinary bladder cancers have marked the cigarette smoking epidemic which started in various countries before or after World War II [ 1 , 2 ]. The incidence rates followed the consumption of cigarettes with a lag time of 20 to 40 years and have started to decline as the number of smokers has diminished [ 3 , 4 ]. Relative risks for tobacco-related lung cancer are of the order of 10 to 20 in active smokers compared to non-smokers, depending on pack-years smoked and other factors, and they remain at levels of 3–5 after 20 years of quitting [ 5 , 6 ].…”

Air Pollution and Mortality: Timing Is Everything

“…Most of the long-term mortality studies have interpreted positive responses as indicating that presence of outdoor ambient pollution caused new cases of chronic disease. I showed that this was not the case for lung cancer [39], because of neglecting timing effects and underestimating smoking effects. There have been few studies of long-term disease progression or morbidity [40].…”