Association between long-term exposure to particulate matter and childhood cancer: A retrospective cohort study.

Although particulate matter is a known carcinogen, its association with childhood cancer is inconclusive. The present study aimed to examine the association between long-term exposure to particulate matter and childhood cancer. A retrospective cohort was constructed from the claims database of the Korea National Health Insurance Service, including children born in seven metropolitan cities in Korea between 2002 and 2012. Monthly mean concentrations of particulate matter with aerodynamic diameter <10 μm (PM 10) and other air pollutants (NO 2 , SO 2 , CO, and O 3) were calculated using data from the AirKorea. Monthly mean concentrations of particulate matter with aerodynamic diameter <2.5 μm (PM 2.5) were estimated based on a data fusion approach. Cumulative exposure was assessed by averaging the monthly concentrations accounting for the residential mobility of the children. The occurrence of cancer was identified by the appearance of diagnosis codes in the claims database. Hazard ratios (HR) and 95% confidence intervals (95% CI) were calculated using Cox proportional regression, adjusting for potential confounders and O 3 concentrations. During the study period, 1,725 patients were newly diagnosed with cancer among 1,261,855 children. HR of all cancers per 10 μg/m3 increment in annual mean concentrations of PM 2.5 and PM 10 were 3.02 (95% CI: 1.63, 5.59) and 1.04 (0.74, 1.45), respectively. PM 2.5 exposure was positively associated with childhood cancer in a large retrospective cohort with exposure assessment accounting for residential mobility. • The association between childhood cancer and PM2.5 was examined. • Long-term exposure to PM2.5 was associated with increased childhood cancer risk. • Retrospective cohort study with health insurance database enabled to observe enough events. • Accounting address change during follow-up made exposure assessment more accurate. [ABSTRACT FROM AUTHOR]