On a chilly Sunday morning beneath Hammersmith Bridge in London, around 40 volunteers participated in a citizen science project aimed at tracking plastic pollution along the River Thames. For nearly a decade, the environmental charity Thames21 has organised these efforts, enlisting volunteers to comb through layers of silt and debris on a 250-metre stretch of foreshore to count and collect flushed wet wipes that persist as a significant source of river pollution.

Volunteers use quadrats—square frames placed on the riverbed—and metal probes to sift through mud, uncovering concealed clumps of wet wipes mixed with plastic, vapes, and other refuse. Dr. Felicity Rhodes, programme manager at Thames21, described the process as unglamorous but vital for creating a robust dataset that provides detailed insight into the scale and distribution of wet wipe pollution along the Thames.

Experts from the Port of London Authority (PLA), including hydrographic surveyors, assist by marking channels and guiding the counting efforts. Jim Powell, a PLA operations manager and surveyor, explained that the location under Hammersmith Bridge is a natural accumulation point due to slower water flow on the inside bend of the river, where debris can trap sediment and other pollutants. This environment encourages materials like wet wipes to build up, creating persistent pollution hotspots.

Many wet wipes contain plastic fibres, which allow them to remain intact even when wet—some are marketed as biodegradable, though this does not guarantee rapid breakdown in the environment. Thames Water estimates that approximately 3.8 billion wet wipes are flushed into its sewage network annually, a volume enough to metaphorically build more than 10 large wet and odorous structures comparable to London’s Big Ben. These wipes predominantly reach the riverbanks through combined sewer overflow events and sewage outfalls.

Last year saw significant interventions aimed at reducing pollution. The long-awaited £4.6 billion Thames Tideway Tunnel, also called the "super sewer," commenced operation to limit raw sewage discharge into the Thames. Shortly afterward, a large-scale cleanup removed "Wet Wipe Island," a 180-tonne mass of compacted wipes spanning 250 metres. Thames21 estimates this effort eliminated some five million wipes from the river.

During the latest survey, volunteers counted 733 wet wipes in 50 sampling squares—a noticeable decline from 1,584 wipes found in the same locations during the previous count in April. While the reduction appears promising, PLA officials caution that such data are preliminary and that factors such as seasonal changes and river conditions might also influence results. Therefore, more sustained monitoring is needed to determine the precise impact of cleanup efforts and new infrastructure.

Looking ahead, Thames21 aims to continue these monitoring sessions to track ongoing trends. The UK government also announced a plan to ban the sale of single-use plastic-containing wet wipes by May 2027, a move supported by advocacy from environmental groups and local politicians, including MP Fleur Anderson.

One volunteer attending with West London Welcome, a community centre for refugees, expressed concern about littering’s environmental impact, highlighting the broader social awareness element of the project. As Dr. Rhodes noted, while wipes will likely continue to wash up for some time, this citizen-led effort is critical to understanding and mitigating the river’s plastic pollution problem before it further impacts marine ecosystems.