Scientists have discovered new evidence to make smokers feel even guiltier about their foul habit.

Not only are the tobacco and chemicals in cigarettes carcinogenic. It turns out that their filters are so toxic that discarded butts have become a major threat to the planet’s health, according to San Diego State University Public Health Professor Thomas Novotny and researcher Elli Slaughter.

“Cigarette butts and other tobacco product waste are the items that are most commonly picked up during urban and beach clean-ups worldwide,” the two scientists wrote in an article published on Tuesday in Current Environmental Health Reports, a scientific journal. “An estimated 4.5 trillion of the annual 6 trillion cigarettes sold worldwide do not end up in a dustbin or ashtray, but are simply flicked away along a roadside or on a pavement. The ban on indoor smoking may have exacerbated this.”

Tipplers throwing aside butts on street corners as they head back to the bar, drivers letting butts fly out the window as they cruise the interstate, teenagers tossing furtive butts into the shrubs, and others dispose of around 110 million pounds of butts a year in the US alone, the study found. Each one contains toxins like nicotine and pesticides in its plastic fibers.

Now, 60 years after the first appearance of the rugged Marlboro Man — an advertising ploy to convince guys to smoke filtered cigarettes that previously had been marketed only to women — the butts are piling up.

The Marlboro Man presumably flicked his used-up smokes onto the open prairie from horseback, or from the top of a butte with a good view. In the real world, marine scientists have discovered whales, sea turtles, birds and, other sea creatures with stomachs packed with the non-biodegradable filters. “They can starve to death for thinking they’re full because of cigarette butts,” Darby Hoover of the Natural Resources Defense Council told VICE News.

Volunteers picked up 340,000 butts from California beaches during a daylong coastal cleanup in 2008, according to legislation recently proposed in Sacramento that would ban selling filters with cigarettes in the Golden State.

Taxpayers are also paying big bucks to clean up butts. California spends $41 million a year sweeping them from the sides of highways, according to a State Assembly analysis of the legislation. San Francisco estimates that collecting butts costs around $6 million a year.

The authors of the San Diego State University study support banning filters and other measures to keep butts from contaminating the ecosystem. “Start a deposit-return scheme for used butts. Hold manufacturers responsible for clean-ups. Place warnings on packets about the impact of simply flicking one’s used cigarettes away,” they write.

Ironically, smokers will probably resist those options because many think cigarette filters screen out the most harmful stuff in cigarette smoke. The National Cancer Institute recently found they do no such thing — it’s just as healthy to roll your own, in other words.

“The filters don’t provide any health benefits,” Sue Vang, a policy analyst at Californians Against Waste, a non-profit group that advocates against litter and pollution, told VICE News. “It’s more of a marketing tool.”

Years ago, cigarette companies sold filters as a healthy option for smokers. Now they refer to a “filtering process” that makes no claims about reducing exposure to smoke’s harmful elements.

On its website, Phillip Morris, for example, posts the ingredients of the filters in Marlboro Reds, including the “tipping papers” around the little beige end of a butt.

“Tipping paper is made from cellulose fiber and may have applied to it various colorants (e.g. pigments to give a cork appearance and/or to add a monogram) and coatings (e.g. to prevent the cigarette from sticking to the lips,” the website says.

Follow John Dyer on Twitter: @johndyerjr