Abstract 833: No association between air pollution and lung cancer incidence in a 2 million South Korean cohort
Authors: Kim Sun-Young , Park Jeongho , Kim Ok-Jin , Shin Miyoun , Kang Sungchan , Hwang Seung-sik , Kim Youngwook , Cho Young-Jae 
Published: March 2024

Abstract
Background: Accumulating evidence has consistently suggested long-term exposure to air pollution as a risk factor of lung cancer incidence. Our previous study of long-term exposure to particulate matter air pollution and lung cancer incidence in a South Korean cohort showed no association with hazard ratios greater than one. This inconsistent finding with those from previous cohort studies could be due to limited exposure assessment relying on district averages and a relatively small sample size of 80 thousand people. The present study aimed to overcome the two major limitations and re-analyzed the association for long-term exposure to particulate matter ≤ 10 µm and 2.5 µm in diameter (PM10 and PM2.5), nitrogen dioxide (NO2), and ozone. Specifically, we improved our exposure assessment for individual exposure using 100-meter grid addresses, and increased the population size to 2 million people based on the National Health Insurance Database (NHID) composed of the entire South Korean population.
Methods: Our study population included 1,976,265 people who aged 30 years or older, had no history of cancer for 2002-2006, underwent health screening for 2005-2007, and resided in the Seoul Metropolitan Area. We defined lung cancer incidence as the first diagnosis based on the International Classification of Diseases 10th revision code and identified the incidence for 10 years of follow-up from 2007 through 2016. We estimated individual long-term exposure to PM10, PM2.5, NO2, and ozone as five-year average concentrations on each year at 100-meter grid addresses of participants’ homes by using previously-validated exposure prediction models. Finally, we applied time-varying Cox proportional hazard model to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for a 10 µg/m3 or 10 ppb increase of each of the four pollutants after adjusting for individual- and area-level characteristics.
Results: Out of 1,976,265 people, 15,707 people (0.79%) developed new cases of lung cancer for 10 years of follow-up. In all analyses for long-term exposure to four pollutants and lung cancer incidence, we did not find an association (PM10: HR= 0.999 [95% CI=0.956 - 1.044]; PM2.5: 0.890 [0.787 - 1.006]; NO2: 1.002 [0.967 - 1.037]; ozone: 1.027 [0.978 - 1.077]). Our stratified analyses by individual and area-level characteristics as well as 79 districts showed that the null findings in the total population were not derived by specific subpopulations.
Conclusion: Despites the considerable improvement in exposure assessment and population size, our findings are contradictory to previous evidence. In addition to the possibility of no association, our null findings could be due to a relatively short period of exposure, the lack of histological information, and exposure measurement error resulting from indoor-outdoor difference and time activity. Future studies should overcome these limitations and re-examine the association.
Citation Format: Sun-Young Kim, Jeongho Park, Ok-Jin Kim, Miyoun Shin, Sungchan Kang, Seung-sik Hwang, Youngwook Kim, Young-Jae Cho. No association between air pollution and lung cancer incidence in a 2 million South Korean cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 833.