Groundwater plumes, the Massachusetts Military Reservation (MMR), and significant breast cancer hot spots. Adjusted, 20 years of Latency. Odds ratios are relative to the whole study area. a) Breast cancer map estimated using indicator variables to signify missing covariate data with an optimal span of 0.15 (Fig. 3c). b) Imputed map drawn using its optimal span of 0.35 (Fig. 5c). c) Location of the MMR and groundwater plumes from the MMR and other sources such as landfills. From a statistical point of view, both span sizes appear to be appropriate. However, because of the low population density around the military base, use of the larger span size tends to merge two "hot spots" in the center and the northwest corner of the map.