Fireworks display could be causing significant microplastic pollution in River Thames

For the last three years, I have investigated the sources and abundance of microplastics within the River Thames and its Estuary as part of my PhD in the Sustainability Research Institute. Whilst plastics within the river are not surprising, as they have been found in even the remotest of regions, I could not find any studies that considered the impact fireworks have on plastic abundance. Arguably every day, a firework is going off somewhere, not necessarily a big display like New Years’ Eve, but small personal displays to celebrate a birthday or a wedding for example. As such, their impact has the potential to be fairly substantial. So, after discussions with my supervisory team, we decided if I wanted to look at the impact of fireworks, I needed to go bigger, and the biggest night for fireworks is New Year. Each year almost every country will have a “main” display, the majority of which are located over water, for example, UK (London), Australia (Sydney harbour), Brazil (Rio de Janeiro, Copacabana beach) and Singapore (Marina Bay. This knowledge resulted in a study on the New Year firework celebrations of 2020 at Westminster, London.

The study was conducted over a nine-day period at Westminster, close to the Millenium Eye, and involved some very early mornings to catch the 1st high tide of the day. Each day 3 Litres of water were collected, filtered, and then examined using light microscopy. Whilst we expected an increase in microplastics’ presence, we did not expect over a 1000% increase from the sample taken on the 30th December 2019 to the one taken 6 hours after the firework display on the 1st January 2020 roughly 24 hours later. The first thing that was evident, however, was the visible colour difference between these samples. This is possibly from soot from the fireworks. However, this cannot be confirmed and must be examined further.

Observed colour differences of water samples taken from the River Thames, Westminster on the 31/12/19 (clear) and 1/1/20(dark). Image taken by Ria Devereux

In total, 2760 pieces of microplastics were found over the course of this study, with 45% of these pieces identified from the sample collected on the 1st of January. Fibres were the most abundant type found, making up 99% of the plastics, and 93% of all plastics identified were black. This is because fibres can enter rivers through multiple sources. The most likely is through clothes shedding fibres during the washing process, which has recently led to talks on filters being fitted into washing machines to catch the fibres and reduce the amount getting into waterways. Rivers, in general, are a significant pathway for plastic pollution, with an estimated 1.15 to 2.41 million tonnes per annum worldwide entering the sea via this route, with 80% of plastic originating from the terrestrial environment.

Mean (± stderr /SE) microplastic total abundance (MPT) per litre in water samples collected in the River Thames, Westminster, London on consecutive days at high tide from the 29/12/19 to 5/1/20 and on the 23/1/20 and rainfall (mm) records during the sampling period

Due to the massive spike on the 1st, rainfall was considered a possible cause. Although rainfall will move water from rivers to the sea faster, it also adds water to the system through sewage treatment works getting overwhelmed or by flooding, which causes an increase in plastic debris entering the system overall. However, we had a very dry few days during this study, and the first sign of rain was after the 1st January, making that possibility very unlikely. The other thing that made us believe this spike was down to the display was that I have been collecting water samples from the River Thames monthly from 2019- 2021 as part of my PhD and never had a reading that high, the closest I have ever got was 61 pieces L-1, which is well off the 510 pieces per L-1 on the 1st January 2020 observed throughout this study.

Microplastics can leach and absorb harmful toxins from the surrounding environment. As a result, it is essential to monitor plastics, as pollutants can be transferred into organisms and result in bioaccumulation and biomagnification within food chains. The effects of microplastics are not just limited to the water system, as microplastics have been found within the soil. This decreases soil fertility, affecting farming and ultimately having devastating consequences on livelihoods and health. As fireworks are not solely used over waterways but also used overland, further studies would be needed to look into the impacts of this. For example, how much microplastic stays within the terrestrial environment and how much makes its way into the water environment?

 During this study, 24 different types of polymers were identified as well as anthropogenic microfibers such as cotton. The most abundant was polychloroprene and polyvinyl chloride (PVC). PVC can have detrimental effects on human health, not just on marine or terrestrial organisms such as cancer, immune system damage and hormone disruption.

Whilst I knew that fireworks already impacted the environment and wildlife, it never occurred to me that the rivers and water systems might be affected. Every year, we are subjected to firework debris littering the streets, or news articles on how much air pollution had been emitted, or domestic animals such as cats and dogs under stress caused by the loud noises from fireworks. While less publicised, there are likely also impacts through disturbance to wildlife such as bats, birds and foxes, and even humans. Some people don’t like fireworks, while others have noise sensitivities or PTSD. One bonus from the Covid pandemic was the introduction of drones and light shows with a smaller number of fireworks or as an alternative altogether. So maybe this is the start of a new kind of New Year celebration, a more sustainable and environmentally friendly one with less environmental impact resulting from firework displays.

With a potential link between New Year’s Eve fireworks events and microplastic pollution identified in this study, further investigation to explore this pattern is warranted.

The research, “Microplastic abundance in the Thames River during the New Year period” has been published in Elsevier – read the full report.

By Ria Devereux

N.B. This article was amended on the 1st April 2022 based on feedback gratefully received.