Seabird eggs contaminated with plastic additives – study A herring gull chick and eggs (Jon Blount/University of Exeter) Herring gull eggs have been found to be contaminated with chemical additives used in plastic production, researchers said. A study looked for evidence of phthalates – a group of chemicals added to plastics to keep them flexible – in newly laid herring gull eggs. The research by the universities of Exeter and Queensland found up to six types of phthalate per egg. The chemicals function as pro-oxidants – potentially causing oxidative stress that can damage cells. Professor Jon Blount, of the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus in Cornwall, said: “Herring gull mothers pass on vital nutrients to their offspring via their eggs.