For air quality, since it is so hyperlocal (e.g. you could have a methcooker around the corner, or new furniture or carpet fumes in the house), the best way would be to get a meter. Some airfilters will provide some measurement, like the Philips ones. I use a little handheld device Temtop LKC-1000S which indicates air quality for PM2.5 and PM10 (µg/m3) particles, HCHO and TVOC. Based on that I will run my air filter for the room that I am in, or before bedtime in the bedroom.
Here is a map site for superfund (the most heavily polluted admitted sites):
https://www.epa.gov/superfund/search-superfund-sites-where-you-live#map
For water pollution, this site has a wealth of info:
https://www.ewg.org/tapwater/