Toxicity
THC has an extremely low toxicity and the amount that can enter the body through the consumption of cannabis plants poses no threat of death. In lab animal tests, scientists have had much difficulty administering a dosage of THC that is high enough to be lethal. It also appears that humans cannot die from ingesting too much THC, unless it were introduced into the body intravenously (See also: Intravenous Marijuana Syndrome).[citation needed] Indeed, a 1988 ruling from the United States Department of Justice concluded that "In practical terms, marijuana cannot induce a lethal response as a result of drug-related toxicity."[24]
According to the Merck Index,[25] the LD50 (dosage lethal to 50% of rats tested) of Δ9-THC by inhalation is 42 mg/kg of body weight. For oral consumption, the LD50 for male rats is 1270 mg/kg, and 730 mg/kg for females—equivalent to the THC in about a pound of 15% THC marijuana.[26]
The ratio of cannabis material required to produce a fatal overdose to the amount required to saturate cannabinoid receptors and cause intoxication is 40,000:1 [12][13]; consumption of such a large dose is virtually impossible. There have been no reported deaths or permanent injuries sustained as a result of a marijuana overdose [14][15][16][17][18]. It is, for all practical purposes, impossible to overdose on marijuana, as the user would certainly either fall asleep or otherwise become incapacitated from the effects of the drug before being able to consume enough THC to be mortally toxic. According to a 2006 United Kingdom government report, using cannabis is much less dangerous than tobacco, prescription drugs, and alcohol in social harms, physical harm, and addiction.[27] It was found in 2007 that while tobacco and cannabis smoke are quite similar, cannabis smoke contained higher amounts of ammonia, hydrogen cyanide, and nitrogen oxides, but lower levels of carcinogenic polycyclic aromatic hydrocarbons (PAHs).[28]