4.5 trillion cigarette butts are littered yearly, and it’s hurting plants, study finds

Smokers cast off roughly 4.5 trillion cigarette butts each year on sidewalks, streets and parks around the world, and now scientists say that — for the first time — they have measured the impact all that litter has on plant life.

Scientists at Anglia Ruskin University in the United Kingdom found in a study published last week that those ubiquitous discarded tobacco products noticeably stunt the germination success and stem length of clover and grass, researchers said in a news release on Friday.

“Many smokers think cigarette butts quickly biodegrade and therefore don’t really consider them as litter,” Dannielle Green, the study’s lead author and a biology lecturer at Anglia Ruskin University, said in a statement. “In reality, the filter is made out of a type of bioplastic that can take years, if not decades, to break down.”

In soil where cigarette butts were present, clover was 27 percent less successful at germinating, its stems were 27 percent shorter, and its roots weighed 57 percent less, researchers said. For grass growing in that same cigarette-tainted soil, germination was 10 percent less successful and shoots were 13 percent shorter, according to the study.

“Ryegrass and white clover, the two species we tested, are important forage crops for livestock as well as being commonly found in urban green spaces,” Green said. “These plants support a wealth of biodiversity, even in city parks, and white clover is ecologically important for pollinators and nitrogen fixation.”

The British academics who carried out the study sampled soil from across Cambridge, including some spots where there were up to 128 littered butts in just one square meter, researchers said.

And with trillions of those butts discarded yearly worldwide, the researchers called cigarette butts “the most pervasive form of plastic pollution on the planet.”

“Dropping cigarette butts seems to be a socially acceptable form of littering,” Green said, adding that “we need to raise awareness that the filters do not disappear and instead can cause serious damage to the environment.”

The study was published in the journal Ecotoxicology and Environmental Safety.

Researchers wrote in the study that “a greenhouse experiment was used to assess the impacts of discarded filters of regular or menthol cigarette, either from unsmoked, smoked, or smoked cigarettes with remnant tobacco, on the growth and development” of the two plant species.

After three weeks, stem length and germination success were measured. Researchers wrote that stem length and seedling success were both “significantly reduced by exposure to any type of cigarette filter for the grass and clover.”

Bas Boots, another biology lecturer at Anglia Ruskin University and a study co-author, said in a statement that “although further work is needed, we believe it is the chemical composition of the filter that is causing the damage to plants.”

“Most are made from cellulose acetate fibres, and added chemicals which make the plastic more flexible, called plasticisers, may also be leaching out and adversely affecting the early stages of plant development,” Boots said.

Research from environmental nonprofit Keep Britain Tidy found that more than 10 percent of smokers don’t think of discarding their butts in the open as littering, according to the BBC.

“These butts are toxic and plastic and cause significant damage when they get into our aquatic and marine environments,” said Allison Ogden-Newton, chief executive of the nonprofit, BBC reports. “Now we know they are having an impact on our plant life too.”

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Jared Gilmour is a McClatchy national reporter based in San Francisco. He covers everything from health and science to politics and crime. He studied journalism at Northwestern University and grew up in North Dakota.