Taken from truthonpot.com (Bold is my highlight)
Many studies have set out to investigate the toxicity of cannabis and its various constituents. These studies measure toxicity levels by determining the median lethal dosage (LD-50). The LD-50 measurement is the point at which 50% of the test animals die (a 50% lethal dosage).
Studies involving small animals such as rats have established an LD-50 point for THC at incredibly high levels (around 1000mg/kg).
Studies involving larger animals such as monkeys and dogs have failed to achieve an LD-50 point, even at enormous doses of over 3000mg/kg.
Although an LD-50 rating has never been established in humans, estimates can be made by extrapolating the results of animal studies.
The non-fatal dosage of 3000mg/kg given in studies of larger animals would be equivalent to an average 70 kg human ingesting 210 grams of pure THC. Given that the average level of THC found in marijuana is
approximately 10%, a person would have to smoke 2.1 kg of marijuana all at once in order to reach the same levels of THC as seen in toxicity studies.
With these numbers in mind, its easy to see why marijuana is far less toxic than everyday substances such as aspirin (LD-50: 200mg/kg) and caffeine (LD-50: 192 mg/kg). In 2008, The Canadian Medical Association Journal published a
review study spanning 30 years of research, concluding that there are no serious adverse effects of using marijuana.
Keep in mind they are talking about MG's of pure THC here, not plant material...
