A mystery glue-like sludge which has been endangering rare seabirds along the south coast was finally identified yesterday as an oil additive used in ship engines.
Experts at the University of Plymouth say the substance is polyisobutene, or PIB, which is added to lubricating oils.
The findings represent a vital breakthrough in the bid to save thousands of birds found on beaches from Cornwall to Sussex covered in the substance.
More than 300, mostly guillemots but also some razorbills, have been treated at the RSPCA West Hatch centre near Taunton, Somerset.
Professor Steven Rowland, a chemical analyst, said PIB was non-toxic but had the consistency of wallpaper glue.
He said: “It’s a mixture and the chemicals involved in it range from oils right through to solids. It’s used and transported around the world as an additive to lubricants.
“It’s not toxic according to manufacturers’ reports but it’s very sticky and glue-like.
The substance could remain in the water for some time because it’s not biodegradable.
He added: “It’s quite big as a molecule, and quite difficult for bacteria and other weathering processes.
“Residues will probably stay around in the environment for some time, though hopefully not in this large mass that pollutes the birds.”
The Maritime and Coastguard Agency and the RSPCA yesterday continued to treat birds covered in the additive.