Mae Sefydliad Iechyd y Byd wedi disgrifio llygredd aer fel y risg unigol mwyaf yn y byd o ran iechyd yr amgylchedd a llygredd sŵn fel yr ail risg fwyaf yng Ngorllewin Ewrop.
The World Health Organisation has described air pollution as the world’s largest single environmental health risk and noise pollution as the second largest risk in Western Europe.