The project was led by the Port of London Authority in partnership with Thames Water Utilities and the environmental charity Thames21. WRc, part of RSK Group, was asked by Thames Water to examine the material in detail to understand the composition of the waste and identify the types of products contributing to the build-up.
WRc Principal Consultant Peter Henley explained that six samples were rinsed to remove river sediment, allowing the team to categorise the remaining items. Twelve material types were identified, including baby wipes, incontinence wipes, wet wipes, cosmetic wipes, panty liners, tampons, unknown plastics, hand towels, fabric and unidentifiable fibrous masses.
The analysis found:
- Eight of the twelve product categories match those commonly found in sewer blockages, suggesting the material originated from sewer discharges.
- All items in these eight categories are considered ‘non-flushable’ and should have been disposed of in the bin.
- Four categories were likely to have entered the river as litter.
- Most items were wipes or wipe-derived material, often entangled into large masses.
- Baby wipes made from polypropylene fibres were present in all samples.
- Period products were identified in five of the six samples.
Peter Henley said the findings align with previous WRc research for Water UK, which shows that more than 60% of sewer blockages are caused by plastic-based wipes. Nationally, Water UK estimates that clearing blockages costs close to £200 million each year.
“These materials simply do not break down in our sewer systems,” Peter said. “When combined with fats, oils and grease, they contribute to blockages and can form fatbergs. If they escape into the environment, they accumulate into large, long-lasting deposits such as those found at wet wipe island.”
Thames Water Pollution Improvement Project Manager Alex Dudfield said the autopsy provided valuable insight following the large-scale removal effort.
“The results will help guide our messaging around the most problematic materials found, reinforcing the importance of only flushing the Three Ps: pee, poo and paper.”
The assessment comes as the UK Government moves ahead with legislation to ban plastic in single-use wet wipes. The draft law passed through Parliament and was announced on 18 November. Following an 18-month transition period, the sale of wet wipes containing plastic will end, with exceptions for specific medical uses. Manufacturers have already committed to phasing out plastic wipes.
However, WRc notes that many other items found in the autopsy—such as sanitary products and plastics—are also entering sewers incorrectly. The organisation emphasises that public awareness remains essential for preventing blockages and protecting the environment.
