Before revision:  Through these substantially different approaches, we robustly obtain that PM_{2.5} levels are the main predictor of R_0 in USA states, with corrections from factors such as other pollutants, prosperity measures, population density, chronic disease levels, and possibly racial composition.
After revision:  Through these substantially different approaches, we robustly obtain that PM_{2.5} is a major predictor of R_0 in USA states, with corrections from factors such as other pollutants, prosperity measures, population density, chronic disease levels, and possibly racial composition.