The studies found that … elevated levels of copper and zinc (but not chromium and tin) were found in sediments at slipping facilities. Significant DDT levels were found in all sampling sites, from Jane Brook to Chidley Point. The levels of DDT ranged from 0.01mg/kg to 4.8 mg/kg (at Royal Freshwater Bay Yacht Club). In addition, Dieldrin was detected at 0.01 mg/kg in Freshwater Bay Yacht Club.
The second study, in particular, showed that the use of anti-fouling paints (containing the pesticide tri-butyl-tin) by boat owners was leading to residues in the river environment. Also that DDT was widespread throughout the river sediments, possibly reflecting its historical use in urban Perth, and much more recent use in agricultural areas….
P49 Monitoring Pesticides – A Review – A Report to the Environmental Protection Authority by Peter A Rutherford. Environment Protection Authority. Perth Western Australia. Bulletin 407. December 1989.