At least 15 sewage plants on England’s south coast use the same contaminated plastic beads that were spilled in an environmental disaster in Camber Sands, Guardian analysis can reveal.

Environmental experts have urged water companies to update these old treatment plants to avoid another catastrophic spill, which can lead to plastic beads being permanently embedded in the environment and killing marine wildlife.

The sewage works in these areas, which include some of England’s most treasured beaches, use billions of floating plastic beads in tanks to purify water. Experts say this is a risky method of treating sewage because of the risk that the beads could spill into the sea if one of the mesh screens holding them fails.

The government and regulators keep no record of which water companies use these beads, where the treatment works using them are located, or how many are in use, a government spokesperson confirmed, adding that it was a “matter for water companies”. This analysis reveals the scale of the problem for the first time.

Campaigners have called for water companies to phase out the beads. Rob Abrams of Surfers Against Sewage said: “Once released, bio-beads behave like any other microplastic: they can be ingested by fish, seabirds and shellfish, enter the food chain, carry harmful pollutants on their surface, and pose risks to human health. And the risk is even greater as so many of these systems sit on the coast. Storms, sea levels rising, and increasingly extreme weather only heighten the chance of failures. Yet instead of investing in safe, modern infrastructure, water companies have siphoned money out to shareholders while letting environmental protections crumble.”

The beads are used to create layers of biofilm, bacteria that purify water. Billions at a time are held in tanks, and all that separates them from the environment is a mesh screen. Most of the sewage works using these beads were built about 30 years ago.

Beverley Coombes, of the plastic pollution nonprofit Strandliners, said: “A loss from a coastal plant is much more of a pollution risk. The discharge goes directly out to sea, where the bio-beads can be carried along the coast for many miles or even across the Channel. I think existing treatment centres should be exploring alternatives to bio-beads. Anything that can stop billions of these potentially toxic bio-beads from entering our rivers and seas has to be a step in the right direction.”

The vast majority of the sewage works using beads are in small towns on England’s south and south-west coastlines, in Sussex, Cornwall, Devon and Dorset. Coastal areas affected include Exmouth, Porthleven, Lyme Regis and Peacehaven.

The Guardian scrutinised water treatment centre applications and reports to build a picture of where they are used, as well as drawing on data from the Cornish Plastic Pollution Coalition, which has been tracking the issue in Cornwall.

Camber Sands in East Sussex faced a spill of an estimated 650m of these beads this month. They have found their way along the coastline, contaminating beaches including Hastings and Dungeness, and buried themselves into the shingle and salt marshes around the area. They were spilled due to a failure of the screen on their tank. Southern Water has apologised and committed to paying for cleanup operations.

These beads contain a high number of polycyclic aromatic hydrocarbons, which have been linked to cancer. They often contain toxins including lead, antimony and bromine. Once in the sea, they attract algae, making them smell like food to sea creatures, which then ingest them and can be poisoned.

England’s coastal communities are some of its most deprived, and they have failed to gain investment over past decades, as tourism habits have changed and people fly abroad instead of visiting the coast.

Helena Dollimore, the MP for Hastings and Rye, said: “Southern Water revealed at my public meeting last week that the use of plastic beads is outdated, and modern treatment works don’t use them. So why is our coastline being put at risk? Southern Water must urgently explain how they will ensure an incident like this never happens again. These beads are contaminating some of our most precious habitats, from the salt marsh at Rye Harbour to the sand dunes at Camber. Our area, and especially our wildlife, will be dealing with these beads for many months to come.”

John Penicud, the managing director for wastewater at Southern Water, said: “In our new plant construction since the early 2000s we don’t use beads any more. We use something called membrane technology.” This uses fixed membranes rather than billions of floating plastic beads, so poses less of an environmental risk.

Penicud blamed the government’s focus on sewage pollution for not retrofitting his sites: “Where we have put forward cases for how we can retrofit some of these sites instead, our focus from government has been to continue to improve the environment by reducing discharges, improving the quality of the sewage that we treat every day.” He added that retrofitting these sites was “always under review”.

Cornish plastics campaigners have battled over this issue for years. Volunteers and beachcombers are still finding beads from a major 2010 spill from the Newham sewage treatment works near Truro. In 2017, vandals slashed some sacks holding beads at a treatment centre, causing a spill on to Tregantle Beach, Whitsand Bay.

The Cornish Plastic Pollution Coalition says it frequently finds beads from more low-level spills along the coast, where they have been handled incorrectly.

South West Water, which owns the sewage treatment plants on that stretch of the coast, was initially planning to phase out beads. Instead, it has replaced the smaller beads with newer, larger ones, which should be less likely to escape.

Claire Wallerstein, from the Cornish Plastic Pollution Coalition, said: “We are very concerned that South West Water is using new beads to extend the use of these old wastewater plants beyond the end of their planned 30-year lifespan – we fear this is a recipe for potential disaster.

“A breach in the containment mesh was what caused the devastating Cornish spill back in 2010 and now, 15 years on, the infrastructure of these plants is surely at even greater risk of rupture.”

A South West Water spokesperson said: “Only eight of our 655 wastewater treatment works use bio-beads, which are all fitted with two levels of robust containment measures and are inspected to ensure beads are kept within the treatment works. Decommissioning these plants is very costly as it requires the whole treatment process to be completely replaced. We are aiming to remove the bio-bead process at our remaining sites when they are required to be upgraded in the future.”

Wessex Water has been contacted for comment.

Where the beads are used

Coastal

• Gorran Haven (South West Water)

• Combe Martin (South West Water)

• Porthleven (South West Water)

• Slapton (South West Water)

• Exmouth (South West Water)

• Lyme Regis (South West Water)

• Plympton (South West Water)

• Eastbourne (Southern Water)

• Peacehaven (Southern Water)

• Sandown (Southern Water)

• Broomfield Bank (Southern Water)

• Beckley (Southern Water)

• Kingston Seymour (Wessex Water)

Inland

• Chilton Trinity (Wessex Water)

• Ivybridge (South West Water)