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Effect modifications by district-level indicators in the NO2 (lag 0–5)-respiratory mortality risk in the total population. P-values indicate the statistical test results on the effect modification (i.e. magnitude of differences in estimates for middle or high-levels compared to low-level; not for the hypothesis that OR is one). %: proportion. NO2: nitrogen dioxide. Odd ratios (ORs) for a 0.01 ppm (10 ppb) increase in NO2
