Personally I've had one small infection from a graze but I don't often slide so it hasn't been a big issue for me. I have trained and played on Wakefield this season and have had sore joints (mainly knees) the day/s after which hasn't been the case after games on the natural fields.
In the case of infections I would encourage your clubs to mention it to CF. Hopefully they get enough feedback to look into it and make sure the parks are being sprayed.
For injuries it's a tough one but I wonder if ACC might have records of turf related injuries and whether or not the introduction of more artificial turfs has had an impact on knee and ankle injuries. They should have a question on their forms asking what surface the injury happened on IMO.