Individual and joint exposure to PM2.5 constituents and incidence of esophageal cancer: evidence from China cancer registry annual report 2019

Background: In recent years, air pollution, particularly fine particulate matter (PM2.5), has been widely recognized as a significant risk factor for various health issues. PM2.5 consists of multiple components, including organic carbon, elemental carbon, and heavy metals, each of which may have varying potential toxic effects on human health. Esophageal cancer is a common malignant tumor worldwide, especially in China, where its incidence and mortality rates remain high. Although studies have suggested associations between air pollution and various cancers, limited research has focused on the specific components of PM2.5 and their associations with esophageal cancer, particularly the impact of joint exposure to different constituents on the incidence of this disease. This study, based on data from the China Cancer Registry Annual Report 2019, aims to explore the association between individual and joint exposure to PM2.5 constituents and the incidence of esophageal cancer, providing scientific evidence for environmental pollution control and strategies for esophageal cancer prevention. Methods: This study analyzed data from the “China Cancer Registry Annual Report 2019” to examine the association between PM2.5 and its major constituents with the incidence of esophageal cancer. Air pollution exposure assessment data were obtained from the Tracking Air Pollution in China (TAP) database. Population density-weighted methods were used to calculate the average exposure levels over different time scales (1-year, 2-year, 5-year). Generalized linear models were employed to assess the relationship between single pollutants and esophageal cancer incidence, while weighted quantile sum regression (WQS) and Bayesian kernel machine regression models (BKMR) were used to analyze the effects of joint exposure to multiple pollutants. Findings: The study found significant associations between exposure to PM2.5 and its components and the incidence of esophageal cancer, particularly within a 2-year exposure window, where the associations were strongest. Specifically, each 1 μg/m³ increase in the concentration of PM2.5 constituents significantly raised the incidence of esophageal cancer: PM2.5 (0.03, 95% CI: 0.02-0.04, P<0.001), nitrate (NO3) (0.14, 95% CI: 0.09-0.19, P<0.001), sulfate (SO4) (0.12, 95% CI: 0.09-0.19, P<0.001), ammonium (NH4+) (0.20, 95% CI: 0.09-0.19, P<0.001), organic matter (OM) (0.10, 95% CI: 0.09-0.19, P<0.001), and black carbon (BC) (0.18, 95% CI: 0.09-0.19, P<0.001). Subgroup analysis showed that female were slightly more affected than male. Analysis of joint exposure revealed that ammonium (NH4+) and nitrate (NO3−) contributed the most to the risk of esophageal cancer. The WQS and BKMR models further confirmed the significant effects of joint exposure to PM2.5 components, with a stronger linear positive correlation observed in the female population. Additionally, the study showed non-linear synergistic interactions between PM2.5 constituents, especially with ammonium intensifying the effects of other components on esophageal cancer incidence. Interpretation: This study indicates that both individual and joint exposures to PM2.5 and its major constituents significantly increase the risk of esophageal cancer. Nitrate and ammonium contributed the most to the combined effects, with gender differences observed, as females were more significantly affected. Non-linear interactions among pollutants further exacerbated this risk. These findings provide important evidence for strengthening air pollution control to prevent esophageal cancer.