Cheng I, et al. - Researchers examined how time-varying air pollution is associated with breast cancer incidence. They estimated air pollutant exposures of particulate matter and oxides of nitrogen by kriging (NO_x, NO₂, PM₁₀, PM_2.5), land use regression (LUR, NO_x, NO₂), and California Line Source Dispersion model (CALINE4, NO_x, PM_2.5) in a cohort of 57,589 females primarily residing in Los Angeles County from recruitment (1993–1996) through 2010. Among all women, they noted a positive—but not significant—association of breast cancer risk with NO_x (per 50 parts per billion [ppb]) and NO₂ (per 20 ppb). African American and Japanese American women exhibited stronger associations of NO_x and NO₂ when subgroup analyses were performed.