An estimated 1.25 billion adults around the world use some form of tobacco. And when they’re done smoking or chewing, many simply toss their cigarette butts or smokeless tobacco packaging onto the ground, according to Johns Hopkins University.

Roughly 4.5 trillion cigarette butts are littered every year, making them the most littered item on the planet, according to WHO. That’s particularly problematic because most cigarette butts contain filters, which are made of nonbiodegradable plastic and contain toxic chemicals that leach into the soil and water. The tobacco industry has historically marketed filtered cigarettes as healthier—despite the overwhelming majority of research suggesting otherwise.

Beyond litter, tobacco harms the environment in other ways, such as requiring forests to be cleared to make room for tobacco farms and using charcoal to cure tobacco leaves.