Cigarette butts harm plant life

In this hot weather, many of us will be flocking to parks and gardens. All too often though you’ll likely come across cigarette butts lying on the grass. And apart from being unsightly, a study from Anglia Ruskin University suggests that these butts can harm local plant life. Danielle Green sprinkled pot plants with cigarette butts and measured the impact they had on how her plants grew. So what did she find? Emma Hildyard caught up with her at the local park to find out...

Danielle - There's one, there's one. Actually, there's a cluster of three yeah, and they are the most common litter item that's found on cleanups and stuff like that, accounting for 30% of litter in some places.

Emma - so we need to get rid of them?

Danielle - Yeah, we need to bin them - bin the butt.

Emma - What made you interested in this study?

Danielle - Walking around the parks and all these beautiful green spaces around Cambridge that we have and just seeing cigarette butts everywhere, and I started to think; “I wonder if this is having an effect on the plants”. It's quite a simple pot experiment where we had either grass seeds or clover seeds, and we had a piece of wood as a control. We had menthol versus regular, we had smoked versus unsmoked to see if it was the plastic in the filter that was having an effect as well. Most cigarette filters are made out of a bio-based plastic called cellulose acetate which is derived from plants essentially. They don't biodegrade very quickly; some studies say two years, some say more than ten. Furthermore, cigarette butts are made up of thousands of tiny little microfibres which are a type of micro plastic essentially, so even when they do break down there's a possibility that they're still persisting as micro plastics.

Emma - So every time we throw a cigarette butt onto the grass we are effectively throwing plastic into the ground and into the ecosystem of the plants?

Danielle - Yeah, exactly. When you’ve smoked a cigarette you're also containing all those toxins from the cigarette into it as well, so there's thousands of different types of chemicals and toxins that have been shown to have effects on different plants and animals, on their own. Nicotine would be the most obvious one. They use cigarette butts in some countries to prevent malaria so they might put them in water bodies to try to kill the larvae of the mosquitoes, for example. So there are some uses for them as well, but it's obviously not what you want.

Emma - In your study you've tested unsmoked cigarettes, smoked cigarettes so just the filter is left, and you've left some tobacco in some of them, so it's half smoked, so what did you see?

Danielle - I expected to see that the ones with the tobacco would have a stronger effect, but overall, even the unsmoked filters had really similar effects to those that were smoked. In some cases there were stronger effects of the smoked cigarettes but overall, the plastic itself is decreasing plant germination and growth, and the root biomass of clover was reduced by around half.

Emma - So the roots are the bit of the plant that take in the nutrients in the water from the soil, so if the root mass is smaller does that mean they get less food and water?

Danielle - Yeah. Similar effects have been found in response to drought, for example. So plant roots might shrink and in this case, first of all they’re not stable, and secondly they're not able to absorb as much water and nutrients as well.

Emma - So they won’t grow as well, they won't grow as fast?

Danielle - Yeah, exactly. There has been another study done in aquatic ecosystems. They also discovered that even the unsmoked butts had an impact on fish, so freshwater and marine fish and could actually lead to mortality. They found a stronger effect of the smoked ones.

Emma - What would you say to people that smoke and throw their cigarettes all over the floor?

Danielle - I'd say it's just as bad as littering any other sort of plastic, and please don't. This study has actually gotten attention worldwide, and there have been quite a few anti-littering campaigners that have been tweeting it and sharing it on their social media. So hopefully there's going to be some action coming from this to either create more bins, raise awareness that they are plastic. Do whatever we have to do to reduce it. There are some studies that are actually recycling cigarette butts and using them as some sort of building materials and stuff like that. So if we can reuse them that would be even better.