The amount of copy on Canadians' cigarette packs just got denser. Ottawa has ordered companies to include amounts of benzene, hydrogen cyanide and formaldehyde contained in a cigarette's smoke on each package. They currently display only data for tar, nicotine and carbon dioxide. As well, makers of chewing tobacco and snuff must now display the amounts of 3 toxic substances — lead, nicotine and nitrosamines — on their packaging.