Rain can be affected by aerosols and fossil fuels

Fossil fuels release toxic chemicals into the atmosphere that can react with other atmospheric molecules to form acids. These acids fall down with precipitation to cause acid rain.

To answer your question about raindrop size, aerosols should be examined. Aerosols are basically just very small particles that tend to float into the air. Once in the air, water more easily collects onto the particles, which results in more, but smaller, water droplets. This doesn’t necessarily mean all water droplets are smaller now when compared to a century ago, but it’s safe to say that areas with more aerosol emissions (like cities) will have smaller but more numerous raindrops.

I hope this somewhat answers your question