Warning sticker on metal wheels package

[Gion]

On the back of the packages of 92421 metal wheels there is a sticker warning about cancer and other nasty effects if the product is used in California. Why is this so? Plastic softener, chemical blackener or what else?

[the Bach-man]

Dear Gion,
This is a label required by California. I saw a similar label on a jetway as I boarded a plane in Anaheim. As long as you don't smoke your wheels, or, I suppose, eat them, you'll be fine!
Have fun!
the Bach-man