Acid rain in some areas close to heavy industry can etch glass. I parked a car of mine outside of Sudbury, Ontario for three days and it etched the glass and the paint. The glass was not too bad but the paint was a mess. Inco the polluter, paid for repairs, being a visitor to the area I knew nothing about this though. The area around Sudbury looked like the Moon, there was no plant life, it slowly got greener as you moved away from Sudbury. Their solution was to build a taller smokestack among other changes.