Polyethylene plastic bags are made from the world's largest commercial polymer, polyethylene, which requires petroleum and toxic materials to manufacture. Most plastic bags end up in landfills or oceans, where they can take over 1000 years to degrade and contribute to pollution. Plastic bags in oceans break down into microplastics that enter the food chain and can ultimately reach humans, threatening wildlife and ecosystems. Many communities have implemented restrictions and bans on plastic bags to reduce their environmental impact.