Public Health Air Quality Act of 2020 This bill requires the Environmental Protection Agency (EPA) to implement policies, programs, and regulations related to air quality monitoring. Specifically, the EPA must implement a program using specified methods and technologies to administer or conduct the best available form of fenceline monitoring (i.e., monitoring of ambient air concentration using technology at a site's property line) of specified stationary sources of hazardous air pollutants. The stationary sources to be monitored must include the 25 high-priority facilities named in the EPA Inspector General report (#20-N-0128) from March 31, 2020, and at least another 25 major sources or synthetic area sources. Among other requirements, the EPA must also determine whether whether to add fenceline monitoring for any additional stationary sources, complete an evaluation and promulgate a determination on whether any existing emission factors must be updated to better reflect or account for the results of fenceline monitoring data collected under the established program, promulgate regulations establishing emission standards for specified source categories, require an additional 80 National Core multi-pollutant monitoring stations, and deploy at least 1,000 air quality sensors to monitor specified pollutants in census tracts or counties with per capita death rates from COVID-19 (i.e., coronavirus disease 2019) that are at least 10% higher than the national average. Finally, the Department of Health and Human Services and the EPA must carry out a Centers of Excellence on Environmental Health Disparities Research grant program to establish and support at least 10 research centers.