The association between ambient PM_2.5's constituents exposure and cervical cancer survival

Increasing evidence links exposure to ambient particulate matter with a diameter less than 2.5 μm (PM_2.5) with reduced survival in cancer survivors, but little was known about the association between PM_2.5 exposure and cervical cancer survival. We analyzed data from 5144 cervical cancer patients diagnosed between January 2014 and December 2020, who completed recommended treatments. Exposure levels were determined by the monthly average concentration of ambient PM_2.5 and its five constituents, obtained from Tracking Air Pollution in China (TAP) based on individual residential addresses. Log-rank tests and multivariate Cox Proportional Hazardous regression were performed to examine the impacts of PM_2.5 and its constituents on overall survival (OS) of cervical cancer patients. We observed that for every increase of 1 μg/m³ in average individual exposure, the hazard ratios (95%CI) for ambient PM_2.5, sulfate (SO₄^2-), ammonium (NH₄⁺), and nitrates (NO₃^-) were 1.078(1.069-1.086), 6.755(5.707-7.996), 2.123(1.935-2.329), and 3.717(3.237-4.267), respectively. Subgroups with longer OS had larger HRs of PM_2.5 and its constituents, which might attributed to more cumulative exposure. No evidence of a threshold for the hazardous effects of PM_2.5 on the OS of cervical cancer patients was identified. Furthermore, long-term exposure to PM_2.5 was negatively associated with pretreatment counts of monocytes, neutrophils, and lymphocytes in peripheral blood of cervical cancer patients. In conclusion, elevated levels of PM_2.5 mass, SO₄^2-, NH₄⁺, and NO₃^- in ambient PM_2.5 exposure were associated with reduced OS among cervical cancer patients. There may be no discernible threshold effect of PM_2.5 on the risk for cervical cancer patients.