From js250's review:

The odor of fresh, new plastic was seriously prevalent when I removed the cap from its box. After about 15 minutes of airing out, it pretty much went completely away. There was no odor whatsoever after about half an hour of airing out.

You know how a plastic shower curtain smells like a plastic factory just threw up in your bathroom when you first take it out of the package and then the smell fades away rather quickly and you never think about it until you have to buy another one? Well, I think that's pretty much the same thing going on here.

Safety ratings are issued for things that go inside of your body, not on your body. I don't think anyone would be exposed to something dangerous just by using a shower cap. less

Eh, some of us have sensitive noses and shower curtains continue to reek for their entire existences. This is why some hardware stores carry cloth shower curtains (which you have to launder pretty frequently, but it still beats your bathroom smelling like shower curtain), or glass-doored showers. less