A controversial herbicide linked to Parkinson's disease has been approved for restricted use in Australia, drawing celebration from grain growers and condemnation from health groups.Paraquat and diquat will remain available for use after the Australian Pesticides and Veterinary Medicines Authority made its final decision after a 30-year review into the chemicals' impacts on human health and the environment."Both chemicals remain available for use with significant new restrictions on application rates and permitted uses," the chemical regulator's chief executive Scott Hansen said."To protect users from acute exposure, new restrictions will phase out backpack sprayers and require enclosed mixing and loading systems...