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Background: Ethylene oxide (EtO) is a carcinogenic gas used in chemical production and to sterilize medical equipment that has been linked to risk of breast and lymphohematopoietic cancers in a small number of occupational studies. We investigated the relationship between environmental EtO exposure and risk of these cancers., Methods: Using the US Environmental Protection Agency's Toxics Release Inventory, we estimated historical exposures for National Institutes of Health-AARP Diet and Health Study participants enrolled in 1995-1996. We constructed 2 metrics at 3, 5, and 10 km: 1) distance between residences and EtO-emitting facilities, weighted by the proportion of time the home was downwind of each facility, and 2) distance-weighted, wind direction-adjusted average airborne emissions index (AEI=∑[lbs EtO/km2]). We estimated risk (hazard ratio [HR], 95% confidence interval [CI]) of incident breast cancer (in situ and invasive) among postmenopausal women (n = 173 670) overall and by tumor estrogen receptor status and non-Hodgkin lymphoma in the full cohort (n = 451 945)., Results: We observed an increased risk of breast cancer associated with EtO-emitting facilities within 10 km (HR[≤10vs>10] = 1.05, 95% CI = 1.00 to 1.10) that appeared stronger for in situ (HR[≤10vs>10] = 1.13, 95% CI = 1.00 to 1.27) than invasive (HR[≤10vs>10] = 1.03, 95% CI = 0.97 to 1.09) disease. Risk of breast cancer in situ was also increased in the top AEI quartiles, and associations weakened with larger distances (HR[Q4vs0] = 1.60, 95% CI = 0.98 to 2.61; HR[Q4vs0] = 1.28, 95% CI = 0.92 to 1.79; HR[Q4vs0] = 1.25, 95% CI = 1.02 to 1.53 at 3, 5, and 10 km, respectively). No differences in breast cancer risk were observed by estrogen receptor status. We found no clear pattern of increased non-Hodgkin lymphoma risk., Conclusions: A novel potential association between EtO emissions and risk of in situ, but not invasive, breast cancer warrants additional evaluation., (Published by Oxford University Press 2023.)

Exposure models are needed to evaluate health effects of long-term exposure to ambient ultrafine particles (UFP; <0.1 μm) and to disentangle their association from other pollutants, particularly PM 2.5 (<2.5 μm). We developed land use regression (LUR) models to support UFP exposure assessment in the Los Angeles Ultrafines Study, a cohort in Southern California. We conducted a short-term measurement campaign in Los Angeles and parts of Riverside and Orange counties to measure UFP, PM 2.5 , and black carbon (BC), collecting three 30-minute average measurements at 215 sites across three seasons. We averaged concentrations for each site and evaluated geographic predictors including traffic intensity, distance to airports, land use, and population and building density by supervised stepwise selection to develop models. UFP and PM 2.5 measurements (r = 0.001) and predictions (r = 0.05) were uncorrelated at the sites. UFP model explained variance was robust (R 2  = 0.66) and 10-fold cross-validation indicated good performance (R 2  = 0.59). Explained variation was moderate for PM 2.5 (R 2  = 0.47) and BC (R 2  = 0.38). In the cohort, we predicted a 2.3-fold exposure contrast from the 5 th to 95 th percentiles for all three pollutants. The correlation between modeled UFP and PM 2.5 at cohort residences was weak (r = 0.28), although higher than between measured levels. LUR models, particularly for UFP, were successfully developed and predicted reasonable exposure contrasts., (Copyright © 2019. Published by Elsevier B.V.)