If there's a question about pathogen transfer via manure application, careful washing or peeling will remove most of the pathogens responsible for disease. Thorough cooking is even more effective at killing pathogens on garden crops. Also, keep human, pig, dog and cat manure out of your compost pile, he warned. Herbicides are also inactivated by binding with organic matter in the compost. If you let your grass clippings decompose on the lawn, or let your compost with treated grass clippings sit for a year or more, this will allow for nearly complete breakdown of the herbicides.
Plants treated with insecticides registered for use on food crops are safe to compost.
Avoid composting chemically treated wood products, such as sawdust from chemically-treated wood. For example, pressure treated wood may contain toxic arsenic, copper and chromium compounds. Avoid composting meat and fatty food wastes that attract pests like rats.