Thousands of tiny 'nurdles' used to make plastic products have been washed up on a Hartlepool beach.
A search of beaches across the UK has found almost three-quarters of them are littered with the lentil-sized pellets which are used as a raw material by industry.
Searches of 279 shorelines in spots ranging from Shetland to the Scilly Isles have revealed 205 of the sites scoured (73%) had the industrial pellets on them.
The largest number recorded in the Great Winter Nurdle Hunt weekend in early February were found at Widemouth Bay, Cornwall, where 33 volunteers collected around 127,500 pellets on a 100-metre stretch of beach.
Hundreds or even thousands of the tiny pellets were spotted by volunteers over a short period of time in locations from Porth Neigwl, Wales, to the shoreline in front of the dunes at Seaton Carew, Hartlepool, and after stormy conditions on the Isle of Wight. A few dozen were also found on the beach at South Shields.
Overall, more than 600 volunteers took part in the Great Winter Nurdle Hunt organised by Scottish environmental charity Fidra in collaboration with the Environmental Investigation Agency, Fauna & Flora International, Greenpeace, the Marine Conservation Society and Surfers Against Sewage.
The small, light-weight nurdles can escape into the environment throughout their manufacture, transport or use, spilt into rivers and oceans or getting into drains where they are washed out to sea, with billions lost in the UK each year.
They are one of the main sources of "primary microplastics" - small pieces of plastic which have not come from larger items broken down into little bits - in European seas and can cause damage to wildlife, such as birds and fish which eat them.
Experts warn they can also soak up chemical pollutants from their surroundings and then release the toxins into the creatures that eat them.
Results from the hunt, which was backed by local community groups and charities, will be fed into the Government's consultation on microplastics, looking at ways of tackling the problem.
Madeleine Berg, projects officer at Fidra, said she was delighted so many nurdle hunters braved the winter weather to take part.
"The information we've gathered will be vital to show the UK Government that pellets are found on beaches all around the UK and, importantly, that so many people care about the issue.
"Simple precautionary measures can help spillages and ensure nurdles don't end up in our environment.
"We are asking the UK Government to ensure best practice is in place along the full plastic supply chain, and any further nurdle pollution is stopped."
Fidra has been working with the UK plastics industry since 2012 to try to promote best practice to end further pellet pollution.