Acid rain does not directly affect human health. It does only indirectly by contributing to sulfate and nitrate particles. So the air quality indices usually do not include direct rainwater pH .

More info here:

http://www3.epa.gov/acidrain/effects/health.html

However but their products (fine aerosols) are regulated and included into air quality indices (PM2.5). See how air quality health index is calculated in Canada:

Stieb DM, Burnett RT, Smith-Doiron M, Brion O, Shin HH, Economou V. A new multipollutant, no-threshold air quality health index based on short-term associations observed in daily time-series analyses

Article in Journal of the Air & Waste Management Association (1995) 58(3):435-50 · March 2008 

Thank you sir for your valuable suggestions.

I think you can and as per as my knowledge no one had ever tried that before. If you can correlate aerosol data and rain quality for a very long period of time there might be chance to find a pattern. i think a parameter can be developed.