Serious health problems can be caused by the AC and the place where you park your car makes a massive difference.
While parking your car in the shade can amass 400-800 mg benzene, leaving it in the sun with temperatures over 16°C, the benzene level can reach 2000-4000 mg (40 times the normal level).
Naturally the first thing you do when you get in the car is turn the AC on with the windows closed.
This affects your kidneys, liver and bone tissue, the benzene causes irreparable damage to them. To prevent this from happening, open the windows and let some fresh air in and after that turn the AC on.
The warmed ventilate from the cooling system is started before the ac starts and in combination with the benzene is the source of many diseases.
Before your next car ride if you intent to use your AC remember to let some fresh air in before you turn on the AC, because this might just be the thing that saves your life.