Real Simple, one of my favorite magazines, had a blurb in its June issue about how to properly toss old bottles of nail polish. They shouldn’t just be thrown in the trash, because they include chemicals that can seep into the water table and contaminate it. All nail polish, even “eco-friendly” kinds, should be dropped off at a household hazardous waste (HHW) facility, along with hairspray and dye, house paints and pesticides. It is easy to locate your nearest HHW at www.Earth911.com by entering the item type and your zip code in the form at the bottom of the page. I recommend calling the facility first to make sure it is still open at the advertised times, and still accepts the item you want to discard.
The article doesn’t seem to be available on-line. Here’s an image of it instead, written by Andra Chantim: