How does greenness contribute to reducing lung cancer risks associated with particulate matter exposure?

Abstract

The increasing global incidence of lung cancer, which now ranks first among all cancer types, along with the highest risk of lung cancer mortality in East Asia and the narrowing gender gap in incidence since the turn of the century, presents a significant and growing public health concern in Chinese cities. This research investigated how greenness affects the relationships between the incidence of lung cancer and PM₁, PM_2.5 and PM₁₀ concentrations via a linear mixed model (LMM) and a generalized linear mixed model (GLMM). The findings revealed that particulate matter was associated with increased incidence of lung cancer, with the most substantial changes observed for PM₁ (4.92), followed by PM_2.5 (4.57) and PM₁₀ (4.22). Our study also revealed that counties with higher levels of greenness experienced a decrease in the incidence of lung cancer among both males and females compared with counties with lower greenness levels, suggesting a protective effect of greenness against lung cancer. The joint associational analysis of particulate matter and NDVI greenness revealed elevated RRs of lung cancer incidence (male: 33 % for PM₁, 40 % for PM_2.5, 30 % for PM₁₀; female: 43 % for PM₁, 51 % for PM_2.5, 42 % for PM₁₀) in high particulate matter and low greenness (the highest-impacted group) relative to those exposed to low particulate matter and high greenness (the least-impacted group). The moderating role of greenness was stronger in females than in males (PM₁: RERI_female = 0.106; PM_2.5: RERI_female = 0.208, RERI_male = 0.043; and PM₁₀: RERI_female = 0.139, RERI_male = 0.017) and more pronounced in areas with medium greenness than in those with high greenness. These findings remained consistent in the smoking-adjusted and region-adjusted models and with an alternative index of the lung cancer mortality rate and greenness. These findings underscored the importance of urban greenness in the development of healthy cities.