Ceir amrywiaeth o lygryddion aer a allyrrir o ddiwydiant a thraffigy mae'n hysbys neu yr amheuir eu bod yn effeithio'n niweidiol ar iechyd pobl a'r amgylchedd. Gall lefelau uwch o lygredd aer a/neu amlygiad hirdymor iddo arwain at symptomau a chyflyrau sy'n effeithio ar y system anadlol a'r system lidiol, a chyflyrau mwy difrifol megis clefyd y galon a chanser hefyd.
A variety of air pollutants emitted from both industry and traffichave known or suspected harmful effects on human health and the environment. Elevated levels and/or long-term exposure to air pollution can lead to symptoms and conditions affecting the respiratory and inflammatory systems, and also more serious conditions such as heart disease and cancer.