Flooding can also cause silting. In the 1980s, anti-fouling paints polluted several major estuaries in NSW, as well as in France, the USA and Great Britain. This causes shell deformities in the Sydney rock and Pacific oysters. In 1989 anti-fouling paints were banned for use on boats under 25m. This has reduced the pollution from paints and shell deformities have declined.
Pollution also comes from sewage and industrial waste put into rivers.
Problems are sometimes the result of government inaction. This occurred in the Georges River region, where sewage pipes were carrying more than 3 times the sewage they were built for. When there were floods, raw sewage overflowed into the river. The farmers have since made moves to protect their stock in such times but the council would prefer to move them than repair the pipes.