Nicotine has a lethal dose at only 40-60mg. The typical accepted LD or lethal dose for many prescription medications is only ten pills. And a the amount of Tylenol in a typical sized bottle is a lethal dose as well. But there is no such thing as a lethal dose of smoked Cannabis sativa. And you don't hear about chain smokers dying from nicotine poisoning, although they probably have very toxic quantities of nicotine in their system. Why are people so worried about one of the safest plants on Earth, Cannabis sativa? If anything, it's probably protecting you from all that harmful crap. And the lethal dose of caffeine is 10 grams, drink to that.