Cannabis smoke ‘has more toxins’. BBCnews, Dec.19, 2007.Cannabis is the most commonly used illegal drug Inhaled cannabis smoke has more harmful toxins than tobacco, scientists have discovered. The Canadian government research found 20 times as much ammonia, a chemical linked to cancer, New Scientist said. The Health Canada team also found five times as much hydrogen cyanide and nitrogen oxides, which are linked to heart and lung damage respectively. [ See ]