Even trace amounts of tobacco can kill.
Need another reason to quit smoking?
Cigarette butts, one of the most ubiquitous forms of garbage in the world, have been found to be toxic to saltwater and freshwater fish.
Even with a small amount of unburnt tobacco clinging to it, a single cigarette butt soaked for a day is enough to turn a liter of water a sickly yellow brown and kill 50 percent of fish swimming in it. Without tobacco, it takes about 4 smoked filters to do the same job.
That's a lot of butts in a small area, and the research team that conducted the laboratory study, led by Elli Slaughter of San Diego State University, is quick to point out that no research has been done yet to test how much poison leaches from butts into ponds, lakes, streams and the ocean.
Still, humans are inadvertently carpeting the planet in cigarette butts. According to one estimate, some 4.5 trillion filters from spent smokes make their way into the environment every year.
When immersed in water, each one becomes a time-released capsule of compounds like nicotine, cancer-causing benzenes, heavy metals and other dangerous compounds.
Team member Richard Gersberg, also of San Diego State University, said that some states and municipalities have begun moving toward legislation that would ban smoking on beaches, where butts are commonly discarded. However, such measures are brought up largely because the filters make for unsightly trash that is hard to pick up.
"I've been a biologist for thirty years. I've even smoked some cigarettes, but I never thought about the chemicals that could leach out," Gersberg said.
Gersberg compared the vast number of discarded butts to the swirl of plastic and refuse in the North Pacific Ocean known as the "Pacific Garbage Patch."
"In my view, cigarette butts are more toxic than a bunch of plastic floating around in the ocean," he said. "You might as well have small vials of toxins -- trillions of them -- in the water."
In the study, researchers tested toxicity on juvenile fathead minnows (Pimephales promelas) and top smelt (Atherinops affinis), fresh and saltwater species that the United States Environmental Protection Agency uses as benchmarks in water pollution studies. The team presented their findings earlier this month at the annual meeting of the American Public Health Association.
"We've got to become intolerant towards this kind of litter, the same way we are towards larger forms of litter," Kathleen Register, executive director of Clean Virginia Waterways, which is associated with Longwood University in Farmville, Va.
"In beach cleanups around the world, cigarette butts are the number one thing volunteers pick up," she added. "So obviously we have an enormous education challenge to inform people about this problem."