Although it may seem easy to throw old nail polish into the trash, it is not something you should do. Nail polish contains toxic chemicals, including formaldehyde and toluene. Which, if not handled properly, can penetrate the ground and contaminate groundwater and soil. So do not pour the nail polish out or throw the bottle directly into the trash.
To dispose of old nail polish, the bottles need to be taken to a hazardous waste collection station. You can search these sites in your area online and send them over. Some communities or cities set hazardous waste collection days to collect used cleaning supplies and similar hazardous waste. Which is an opportunity to properly dispose of nail polish.
If none of this is possible for you, some networks suggest removing the nail polish cap, letting it solidify, and then putting the bottle in the trash can, but this should not be your first choice.
If your nail polish is good, but you are tired of its color and brand, you can consider giving it to teenagers. Teenagers love to paint bright colors on their nails, and they may make good use of your old nail polish. So you don’t need to throw them in the trash or send them to a waste recycling bin. Of course, you can also use old nail polish to repair the scratches on the shoes or to decorate the keys, see this article for details：What To Do with Old Nail Polish?
If you concern about the effects of some chemicals in nail polish on health, especially for pregnant women, <Is It Ok to Get nails down while pregnant >can give you the answer? Now some big brands of nail polish are removing or reducing the toxic chemicals in nail polish.
These results can be found in the online cosmetics database. These databases list the ingredients in cosmetics and give them a numerical rating. Even if you buy more environmentally friendly nail polishes, you still need to properly dispose of them at hazardous waste collection sites.
In fact, the US Environmental Protection Agency has added nail polish and nail polish remover to the list of dangerous products, which makes them illegal if not handled properly. All cities in the United States require hazardous waste disposal sites. You need to take your nail polish there to get proper and professional disposal.