Once the cygnets have hatched, you might try to capture the parents and cygnets and move them to a better area with less pollution. We know that swans are protected in England, so there may a legal issue with you doing this. We would suggest you contact Wendy Hermon at Swan Lifeline Rescue Facility in Eton (contact info can be obtained by searching internet). Wendy and her staff do a great job of rescuing swans and they may have a better solution since we are not readily familiar with the area. The Regal Swan