Smoking and air pollution exposure and lung cancer mortality in Zhaoyuan County

Simultaneous exposure to high levels of air pollution and high tobacco consumption at the same place is rare. The aim of the present study was to evaluate the impact of the two factors on the risk of developing lung cancer.

Data on the number of deaths due to lung cancer and on population from 1970 to 2009 were obtained from Zhaoyuan County. Data on the smoking populations were obtained at random sampling survey during the time in Zhaoyuan. Data on the components of atmospheric surveillance were obtained from the local environmental protection offices. Logarithmic linear regression and general log-linear Poisson age-period-cohort (APC) models were used to estimate age, period, cohort, gender, smoking, and air pollution effects on the risk of lung cancer mortality.

The standardized mortality rates of lung cancer drastically increased from 8.43 in per 100 000 individuals in the 1970-1974 to 25.67 in per 100 000 individuals in the 2005-2009 death survey. The annual change of lung cancer mortality was 3.20%. In the log linear regression model, the age, proportion of smokers, gender, period, and air pollution are significantly associated with lung cancer mortality. The APC analysis shows that the relative risks (RRs) of gender, smoking, and air pollution are 2.29 (95% confidence interval (CI): 2.16-2.43), 3.05 (95% CI = 2.76-3.36), and 1.42 (95% CI = 1.19-1.69), respectively. Compared with the period 1970-1974, high RRs were found during 1995-2009. Compared with the birth cohort 1950-1954, the RRs increased in the birth cohorts of 1910 to the 1940. Compared the aged 35-59 and 60-84 in the 1980-1984 death survey (not exposed to air pollution) with that in the 2005-2009 death survey (exposed to air pollution), The two age groups exposed to air pollution, 25 years later, had an increased mortality rates for lung cancer by 2.27 and 3.55 times for males and by 1.47 and 3.35 times for females.

The mortality rates of lung cancer drastically increased in the past 35 years. The trend of lung cancer mortality may be in a great extent possibly due to the effects of combined smoking and air pollution exposure.