| Region | Communities, n | Level 1 | Level 2 | Level 3 | Level 4 | Difference (level 4–1)* | |
| Current day | Northeast | 15 | 1.02 (−1.67 to 3.13 ) | 4.82 (2.43 to 7.70) | 5.45 (1.91 to 10.23) | 11.20 (6.44 to 16.17) | 10.18 (4.79 to 15.78) |
| Industrial Midwest | 19 | 1.44 (−0.69 to 3.58) | 4.74 (2.45 to 6.76) | 3.79 (1.06 to 6.17) | 9.72 (6.34 to 13.05) | 8.28 (4.35 to 12.07) | |
| Upper Midwest | 7 | 0.07 (−5.15 to 2.97) | 4.25 (0.75 to 7.40) | 3.53 (−1.62 to 7.65) | 6.18 (−1.16 to 11.99) | 6.10 (−2.32 to 13.80) | |
| Northwest | 12 | 0.65 (−2.24 to 2.96) | 3.63 (0.02 to 6.32) | 4.80 (1.80 to 8.12) | 9.09 (5.35 to 12.87) | 8.43 (3.83 to 13.18) | |
| Southeast | 26 | 1.22 (−1.05 to 3.30) | 4.18 (1.43 to 6.54) | 3.02 (0.05 to 5.58) | 7.23 (2.84 to 10.51) | 6.01 (1.01 to 10.23) | |
| Southwest | 9 | 1.65 (−0.95 to 4.82) | 4.59 (1.66 to 7.72) | 4.07 (0.48 to 7.78) | 6.43 (0.80 to 10.85) | 4.78 (−1.61 to 10.04) | |
| Southern California | 7 | 2.08 (−0.43 to 5.04) | 4.27 (1.12 to 6.81) | 5.47 (2.62 to 9.05) | 8.55 (4.47 to 13.28) | 6.46 (1.44 to 11.88) | |
| National | 95 | 1.17 (−1.06 to 3.06) | 4.35 (2.12 to 6.41) | 4.31 (1.59 to 7.08) | 8.31 (4.22 to 11.99) | 7.15 (2.63 to 11.40) | |
| Lag 1 | Northeast | 15 | 1.08 (−1.66 to 3.65) | 4.53 (2.00 to 7.67) | 4.95 (1.77 to 9.07) | 10.59 (6.18 to 15.52) | 9.50 (4.50 to 15.14) |
| Industrial Midwest | 19 | 1.47 (−2.05 to 6.32) | 4.22 (2.06 to 6.52) | 4.23 (1.82 to 6.44) | 9.96 (6.55 to 13.58) | 8.49 (2.78 to 13.60) | |
| Upper Midwest | 7 | −0.46 (−5.13 to 2.76) | 3.70 (0.42, 6.88) | 3.74 (−1.08, 7.07) | 6.94 (0.10 to 12.36) | 7.39 (−0.33 to 14.68) | |
| Northwest | 12 | 0.02 (−2.87 to 2.47) | 3.01 (−0.27 to 5.61) | 4.59 (1.90 to 7.39) | 9.37 (5.66 to 13.19) | 9.35 (4.93 to 14.13) | |
| Southeast | 26 | 0.73 (−1.85 to 2.73) | 3.62 (0.91 to 6.01) | 3.82 (0.72 to 6.07) | 7.17 (3.42 to 10.45) | 6.44 (1.81 to 10.57) | |
| Southwest | 9 | 0.73 (−1.85 to 2.73) | 3.89 (0.85 to 7.09) | 4.03 (0.27 to 7.04) | 7.27 (1.78 to 11.17) | 6.18 (−0.15 to 11.29) | |
| Southern California | 7 | 1.68 (−0.99 to 4.88) | 3.12 (−0.78 to 5.96) | 5.10 (2.45 to 8.37) | 8.95 (4.89 to 13.71) | 7.26 (2.14 to 12.79) | |
| National | 95 | 0.80 (−1.63 to 3.26) | 3.73 (1.47 to 5.94) | 4.35 (1.93 to 6.56) | 8.62 (4.85 to 11.99) | 7.82 (3.25 to 12.11) |
*Difference of the Bayesian meta-analysis between level 4 (highest) and level 1 (lowest) of maximum hourly ozone concentration; the values in the parentheses are 95% posterior intervals (PI).