To be fair it is only a problem with certain clubs, namely LFC. I have a great view of the South stand upper tiers from my seat in East Stand Upper. With Chelsea it was very few items and looked like empty plastic glasses so the chance of injury was not high. It is always a problem with Liverpool fans just as it is at Anfield. The easiest solution is just to ban them or drastically reduce their allocation. Most other opposition fans don't behave like animals.
Unfortunately City won't do that as they've now got a new memorandum of understanding with Liverpool Football Club.
If City tried to reduce Liverpool's ticket allocation the cult would kick off and the clubs would be at loggerheads again, after just agreeing to work together and to get on better with each other.