Health impacts of local air pollution reduction used an exploratory epidemiological method- ology similar to that presented in Pope et al. (2009). Specifically, we used the simulated health data at census block group level (derived from county-specific health data and census information on demographics) to evaluate dif- ferent strategies for demonstrating impacts of relatively small changes in ambient pollution (compared to NOx) over multiple years. The outcomes for this analysis were the differences between the number of hospital- izations for 2001 and 2010, as illustrated by Equation 3: ΔHC = (H2010 – H2001)C , [3] where ΔHC is the change in the number of hospitalizations at census block group C and H2010 and H2001 are the number of hospitaliza- tions for the years 2010 and 2001, respectively. We calculated the number of hospitaliza- tions due to congestive heart disease [CHD; International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9CM; World Health Organization 2004), code 428] and asthma (ICD-9CM, code 493) for each census block group for the years 2010 and 2001. We chose these end points based on sig- nificant associations (1.28% increase in risk per 10-gμ/m 3 increase in same-day PM2.5) reported by Dominici et al. (2006) between PM and CHD hospitalizations for the Medicare cohort. We restricted hospitalizations due to CHD to the population > 65 years of age, and we calcu- lated asthma hospitalizations separately for all ages and for the population < 25 years of age, because of known age-dependent differences [Connecticut Department of Public Health (CDPH) 2007]. We calculated the number of hospitalizations for the years 2001 and 2010 as HC = 2001 (CDPH 2001) and 2007 (CDPH 2007), and we used 2007 data for 2010 hospitaliza- tions. The rates are broken down by age and sex, and age and race, but not by age, sex, and race. We therefore assumed constant ratios of rates of hospitalizations for males and females for all races. We calculated hospitalization rates according to sex, race, age (> 65 years of age for CHD, all ages, and < 25 years of age for asthma), health outcome (CHD or asthma), and year (2001 or 2010) as / ^Rate # PopC hFR + ^Rate # PopC hMR , [4] i = R RateFR = where Hc is the number of hospitalizations for census block group C, Rate is the rate of hos- pitalization for females (F) and males (M) of race R (white, Hispanic, black), and PopC is the population of each subgroup (e.g., white female, black male, etc.). We used 2000 U.S. Census Bureau (2001) data to estimate the size of each population subgroup in 2001. We used county-level population projections for 2010 to estimate the proportional change in each population subgroup from 2000 to 2010 and applied this to the 2000 census block group population to estimate 2010 census block populations for each subgroup. Hospitalization rates for both outcomes are available for all of New Haven County for RateR ^PopMR + PopFRh ^Ratio of ratesM/F # PopMRh + PopFR . [5] For example, RateFR is the county-level hospitalization for females of race R; RateR is the county-level hospitalization rate for race R; Ratio of ratesM/F is the ratio of hospitaliza- tion rates between males and females; and PopFR and PopMR are county-level population sizes for females and males of race R, respec- tively. We then calculated RateMR by multi- plying RateFR by Ratio of ratesM/F. Reductions of PM2.5 at each census block group were then regressed against the changes in hospitalizations from 2001 to 2010 at each census block group. All regression analyses were performed using SAS (version 9.1; SAS Institute Inc., Cary, NC). PM2.5: < 8 µg/m3 8–12 µg/m3 12–14 µg/m3 14–16 µg/m3 16–20 µg/m3 > 20 µg/m3 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) 2020 PM2.5 2020 NOx 2030 PM2.5 2030 NOx ) 18 4584 e on4582 z ,M4580 T U4578 (km4576 e nc4574 a ts 4572 i d th4570 u so4568 – trh4566 o N ) 18 4584 e on4582 z ,M4580 TU4578 (km4576 ce4574 n tsa4572 i thd4570 u so4568 – trh4566 o N 2001 PM2.5 2001 NOx 2010 PM2.5 2010 NOx 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) 664 666 668 670 672 674 676 678 680 682 East–west distance (km UTM, zone 18) NOx: < 20 µg/m3 20–40 µg/m3 40–60 µg/m3 60–80 µg/m3 80–100 µg/m3 > 100 µg/m3 Figure 1. Maps of modeled PM2.5 and NOx concentrations for 2001 (baseline), 2010, 2020, and 2030. Environmental Health Perspectives • volume 119 | number 4 | April 2011 489