:scared: Sorry to hear about your wheels Lynn! I don't think this would have happened with just A2Z, although it IS quite strong and effective. It's possible that you would have had problems with most wheel cleaners if it sat that long.
I think a lot of chemicals, especially wheel cleaners, can be dangerous if you let them concentrate too highly. Depending on how warm the weather is or how warm the wheels are, wheel cleaner can dry out surprisingly quickly. Once you let a liquid chemical dry out, it super-concentrates and can get very dangerous. This is similar to how people get acid rain damage on their cars.
I haven't had a problem with wheel cleaners yet personally, and I've tried quite a few. On the other hand, I never let the stuff dry out on me if I have to scrub it or otherwise let it sit for very long. I either rinse it off, or quickly hit it with the "mist" setting on my water spray gun to keep it wet.