This prospective cohort study conducted in China aimed to assess the association between long-term exposure to fine particulate matter (PM2.5) and risk of esophageal cancer. The study included over 510,000 participants without esophageal cancer at the beginning of the study and used a high-resolution satellite-based model to estimate PM2.5 exposure levels during the study period. The findings indicate a linear concentration-response relationship between long-term PM2.5 exposure and esophageal cancer incidence (primarily squamous cell carcinomas). Specifically, for each 10-microgram per cubic meter (µg/m3) increase in PM2.5 concentration, there was a 16% higher risk of cancer (95% confidence interval: 4 – 30%). Those in the highest quarter of PM2.5 exposure had a 1.32-fold higher risk compared to those in the lowest quarter.
The authors also estimated the population attributable fraction, which represents the proportion of esophageal cancer cases that can be attributed to PM2.5 exposure, and reported that nearly one-quarter (23.3%) of esophageal cancer risk could be attributed to annual average PM2.5 concentrations of 35 µg/m3 or higher, which was higher than the risks attributable to lifestyle risk factors such as heavy alcohol consumption or current smoking.
It is important to note that previous cohort studies conducted in the United States showed mixed results regarding the association between PM2.5 and esophageal cancer mortality. The differences in findings between the Chinese and US studies may be attributed to variations in PM2.5 levels, the predominant histologic subtype of esophageal cancer (ESCC in China and adenocarcinoma in the US), and differing characteristics of the populations. As the authors note, some strengths of the study include the large sample size, long follow-up period, and high spatiotemporal resolution of the exposure assessment model and the ability to control for multiple potentially confounding factors.
Overall, the study provides intriguing epidemiological evidence supporting the association between long-term PM2.5 exposure and an increased risk of esophageal cancer, particularly ESCC. As populations across the world are more frequently experiencing elevated fine particulate concentrations resulting from wildfires and other sources, these findings merit following up to determine whether they are causal and to better understand the mechanisms.
Long-Term Exposure to Fine Particulate Matter and Incidence of Esophageal Cancer: A Prospective Study of 0.5 Million Chinese Adults.
Sun D, Liu C, Zhu Y, Yu C, Guo Y, Sun D, Pang Y, Pei P, Du H, Yang L, Chen Y, Meng X, Liu Y, Zhang J, Schmidt D, Avery D, Chen J, Chen Z, Lv J, Kan H, Li L; China Kadoorie Biobank Collaborative Group.
Copyright © 2023 The Authors.
BACKGROUND & AIMS: Evidence is sparse and inconclusive on the association between long-term fine (PM2.5 mm) particulate matter (PM2.5) exposure and esophageal cancer. We aimed to assess the association of PM2.5 with esophageal cancer risk and compared the esophageal cancer risk attributable to PM2.5 exposure and other established risk factors.
METHODS: This study included 510,125 participants without esophageal cancer at baseline from China Kadoorie Biobank. A high-resolution (1 x 1 km) satellite-based model was used to estimate PM2.5 exposure during the study period. Hazard ratios (HR) and 95% CIs of PM2.5 with esophageal cancer incidence were estimated using Cox proportional hazard model. Population attributable fractions for PM2.5 and other established risk factors were estimated.
RESULTS: There was a linear concentrationresponse relationship between long-term PM2.5 exposure and esophageal cancer. For each 10-mg/m3 increase in PM2.5, the HR was 1.16 (95% CI, 1.04–1.30) for esophageal cancer incidence. Compared with the first quarter of PM2.5 exposure, participants in the highest quarter had a 1.32-fold higher risk for esophageal cancer, with an HR of 1.32 (95% CI, 1.01–1.72). The population attributable risk because of annual average PM2.5 concentration 35 mg/m3 was 23.3% (95% CI, 6.6%–40.0%), higher than the risks attributable to lifestyle risk factors.
CONCLUSIONS: This large prospective cohort study of Chinese adults found that long-term exposure to PM2.5 was associated with an elevated risk of esophageal cancer. With stringent air pollution mitigation measures in China, a large reduction in the esophageal cancer disease burden can be expected.