Epidemiological Evidence That Air Pollutants May Accelerate or Delay Breast Cancer Mortality: A Retrospective Cohort Study.

Purpose: To explore the effects of long-term exposure to air pollutants on risk of death and survival time of breast cancer patients. Methods: We retrospectively collected data of 4,438 primary breast cancer patients treated at the Affiliated Tumor Hospital of Xinjiang Medical University between January 1, 2014, and May 31, 2023. We analyzed the effects of single and multiple pollutants on mortality risk using both univariate and multivariate Cox proportional hazard models. Meanwhile, we employed the Cox model to investigate the interaction between pairs of air pollutants. Then, an accelerated failure time (AFT) model was used to quantify the effects of air pollutants on the survival time of breast cancer patients, quantifying whether they accelerate or delay survival. Results: The multivariate Cox model revealed that the highest quartile (Q4) of SO2 (HR=11.96, 95% CI: 4.68-30.55), CO (HR=4.58, 95% CI: 2.82-7.44), NO2 (HR=3.83, 95% CI: 2.50-5.86), PM2.5 (HR=2.67, 95% CI: 1.88-3.80), and PM10 (HR=2.67, 95% CI: 1.88-3.80) significantly increased the risk of breast cancer mortality. In contrast, O3 showed a dose-dependent protective effect (HR=0.19, 95% CI: 0.08-0.21). NO2 significantly increased risk of death in breast cancer patients after introduction of particulate matter. The accelerated failure time model further revealed that SO2 (Q4-TR=0.18, 95% CI: 0.08-0.41) and CO (Q4-TR=0.20, 95% CI: 0.12-0.33) reduced survival time to 18%-20% of the reference group (Q1). O3 demonstrated a dose-dependent reduction in mortality risk (Q4-TR=7.29, 95% CI: 4.51-11.78); Notably, NO2 and particulate matter (PM2.5, PM10) had a bidirectional effect-low concentrations (Q2-Q3) extended survival time (TR: 1.47-2.64), while high concentrations (Q4) accelerated death (TR: 0.26-0.39). Conclusion: Air pollution collectively impacts breast cancer mortality, with complex pollutant interactions modulating risk. This highlights the need for holistic environmental health strategies.