The most pervasive form of plastic pollution on Earth isn’t plastic bags or even plastic straws. It’s cigarette butts. Every year, an estimated 4.5 trillion cigarette butts, containing plastic filters, are littered by the 76 to 84 percent of smokers who toss the ends of a smoke rather than disposing of them into a trashcan or ashtray.
The choice to pollute with a cigarette butt may seem small, but it brings repercussions over time.
Most recently, scientists from England’s Anglia Ruskin University discovered that cigarette butt litter can significantly harm plants. In a paper published July 18 in Ecotoxicology and Environmental Safety, they report that the presence of butts in soil harms how well clover and grass germinated and grew.
“Many smokers think cigarette butts quickly biodegrade and therefore don’t really consider them as a litter. In reality, the filter is made out of a type of bioplastic that can take years, if not decades to break down.”
After Green and her team surveyed three of the largest parks in Cambridge, England, they found an average of 2.6 butts per square meter, with a maximum of 126 butts per square meter near park benches specifically. This prompted a burning question: What was the cost of all these cigarettes?
To figure that out, the team added cigarette butts to pots with either perennial ryegrass or clover seeds. These species are commonly found in urban green spaces and are important forage crops for livestock. White clover is also considered ecologically important because it provides nectar to pollinators and fixes nitrogen in the soil.
One group of pots received the butts from smoked and unsmoked regular and menthol cigarettes, while the other received small wooden dowels in their soil as a control object. After 21 days, shoot length (how tall a stem grows) and germination success were significantly reduced by exposure to both types of cigarettes in both plant species. Cigarette butts cut down germination and shoot length of clover by 27 and 28 percent, respectively, while the same factors were reduced in the grass by 10 and 13 percent. The clover also grew 57 percent less weight in roots.
While it’s previously been established that one littered cigarette filter can contaminate plants with nicotine, the fact that the filters of unsmoked cigarettes still harmed these plants shows that the filter is probably an overlooked source of damage. Most cigarette filters are composed of up to 12,000 cellulose acetate fibers, which can take between 7.5 and 14 years to break down in the environment. Although further work is needed to know exactly how the filters harm plants, the team hypothesizes that chemicals called plasticizers — which are added to the fibers to make them more flexible — could be doing the damage.
With a little over a billion people around the world who smoke cigarettes, Green suggests that the most immediate solution to the issue is the adoption of cigarette butt deposit schemes, in which cigarette manufacturers are forced to offer money in exchange for returned butts. San Francisco has already initiated a 60-cent per pack fee as a way to raise money that can be used to clean up discarded cigarette filters.
Meanwhile, some advocates argue for banning filters outright. The idea behind filters is that they block the dangerous chemicals in smoke, but they also make it easier to take deeper puffs and inhale more smoke overall.
And this new research suggests they may be doing more harm than previously suspected.
Cigarette filters (butts) are currently the most abundant form of anthropogenic litter on the planet, yet we know very little about their environmental impacts on terrestrial ecosystems, including plant germination and primary production. When discarded, filters contain a myriad of chemicals resulting from smoking tobacco and some still contain unsmoked remnants. 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 Lolium perenne (perennial ryegrass) and Trifolium repens (white clover). After 21 days, shoot length and germination success were significantly reduced by exposure to any type of cigarette filter for the grass and clover. Although total grass biomass was not measurably affected, the root biomass and root:shoot ratio were less in the clover when exposed to filters from smoked regular cigarettes and those with remnant tobacco. Cigarette filters caused an increase in chlorophyll-a in clover shoots and an increase in chlorophyll-b in grass shoots. Accordingly, whilst the chlorophyll a:b ratio was increased in the clover exposed to cigarette filters, it was decreased in grass. This study indicates the potential for littered cigarette filters to reduce growth and alter short-term primary productivity of terrestrial plants.