Several countries blocked moves to add chrysotile asbestos to a list of dangerous substances subject to export restrictions under the Rotterdam Convention, a UN spokesman said Friday. Canada, Ukraine, Kazakhstan, Kyrgyzstan and Vietnam all objected to the move, said a spokesman for the UN environment programme, Michael Stanley-Jones. \"That chemical will come then before the next conference of the Rotterdam parties in 2013,\" he added. Asbestos is used in insulation and fire protection but in some forms is a highly dangerous cancer-causing material Explaining his country\'s position, Henry Lau, a Canadian official noted that \"scientific examinations confirm that the fibres of chrysotile can be used without danger and under controlled conditions.\" States signed up to the treaty decided to add two other toxic substances -- the herbicide alachlor and an insecticide aldicarb -- to the list. Importing countries will now have to issue proof they are aware of the dangers involved in using the product and that they agree to its import after having received relevant information from the exporting country. About 40 products are subject to such export restrictions under the treaty, which came into force in 2004.