Dozens of Victorian shearers may have been unknowingly poisoned by a chemical linked to the manufacture of nerve gas, unions say. The Australian Workers Union is contacting shearers who think they have been exposed to the chemical diazinon, found in many sheep dips. Mr Bill Shorten, AWU organiser, said many shearers may have been poisoned by using diazinon products in confined spaces or through getting it on their clothes and skin.