Ambient Fine Particulate Matter, Residential Greenness, and Childhood Cancer Risk by Trimester of Exposure in Minnesota 2000 to 2014: A Case-Control Study

BACKGROUND: Outdoor air pollution is a suspected risk factor for childhood cancer, and there is some evidence that greenness may reduce cancer risk. We examined relationships between prenatal exposure to ambient fine particle air pollution [particulate matter <2.5 µg/m3 (PM2.5)], greenness, and childhood cancer risk in Minnesota. METHODS: Cases included individuals born in the state of Minnesota and reported to the Minnesota Cancer Reporting System between 2000 and 2014 (n = 1272, ages 0-14 years at diagnosis) and birth year-matched cancer-free controls (n = 5245). We used Network Common Data Form to estimate monthly PM2.5 exposure and the normalized difference vegetation index for census tract-level greenness. We estimated ORs and 95% confidence intervals (95% CI) between high PM2.5 (≥12 µg/m3) and normalized difference vegetation index (≥0.3) exposure and each childhood cancer per trimester (T1, T2, and T3) and full pregnancy using adjusted logistic regression. RESULTS: High PM2.5 exposure was associated with increased odds of Burkitt lymphoma [ORT1: 1.93 (1.13-3.30)], lymphoreticular neoplasms [ORT1: 1.43 (1.01-2.01)], Hodgkin lymphoma [ORT2: 2.60 (1.52-4.45)], lymphoid leukemias [ORT3: 1.17 (1.01-1.37)], B-cell leukemia [ORT3: 1.20 (1.02-1.41)], and intracranial and intraspinal embryonal neoplasms [ORT3: 1.90 (1.07-3.37)]. High residential greenness during early life was associated with reduced risk of malignant epithelial neoplasms and melanomas [ORT1: 0.34 (0.13-0.91)]. Unexpectedly, greenness was also associated with increased risk of renal tumors [ORT2: 1.52 (1.11-2.08); full pregnancy OR: 1.30 (0.98-1.72)] and neuroblastoma [ORT3: 1.44 (1.03-2.03)]. CONCLUSIONS: We observed elevated risk associated with PM2.5 exposure throughout pregnancy for multiple individual cancers, namely leukemias, lymphomas, and central nervous system tumors. IMPACT: These findings demonstrate the complex relationship between PM2.5 and greenness.