Cigarette filters are made of 12,000 individual strands of a high-grade plastic called cellulose acetate. Cellulose acetate is also used to make sunglasses, textiles, good old-fashioned photographic film, personal hygiene products, and more.
Cigarette filters look like cotton, paper, or some other kind of natural fiber, because cellulose acetate is derived from cotton in a complex way I finally understand after reading Patricia dePra’s explanation.

Cellulose acetate is used instead of natural fibers such as cotton or paper because it holds up against heat and moisture—handy and practical features to have at the mouth-end of a lit cigarette—and because it’s cheaper and more uniform to manufacture than biodegradable alternatives.

Most smokers don’t litter other forms of plastic. And, people as a rule avoid deliberately contaminating their environment—most wouldn’t toss dead batteries off the dock or down a storm drain. But it’s still common practice to flick a plastic butt loaded with lead, cadmium, arsenic, nicotine, and other toxins on to the ground, where they leach these nasty contaminants into the water and soil, threatening life on land and at sea. Just one smoked cigarette butt was found to kill half the fish in one liter of water.

Why do smokers do this? I wish I could tell you. I’m a former smoker, and I did it too. I can tell you that I didn’t know that cigarette butts are plastic—and never thought about the toxins they trap. Nor did much thought or awareness go into that flick. It was just what you did when you finished your cigarette.

Some who study this will say that it’s because smokers want to distance themselves from their habit, and subconsciously that may be true, but mostly I think it’s because cig butts stink to high heaven and there’s often nowhere to safely toss them out. Not an excuse, I know. But it is a reason. Until we’re aware that our actions cause harm, we have no reason to change them.

The real rub is that cigarette filters do not reduce the harm of smoking, and may in fact increase it. They’re a marketing tactic used by tobacco companies to sell more cigarettes. Filters require smokers to draw more heavily on the cigarette when they take a puff, and smoke more cigarettes to get the same nicotine fix.

It’s maddening that the most littered item in the world is not only toxic and plastic, but completely unnecessary. Here in San Francisco, Surfrider’s Hold on to Your Butt program is working to change this by educating smokers, installing cigarette receptacles, advocating for enforcement of littering laws, and demanding that big tobacco get their plastic out of smokers’ butts. Together, we can keep this toxic trash out of our environment.