Taken from this URL: http://www.everything2.com/?node_id=1923488
The lethal dose of water
Fiction -
"..is eight gallons an hour!1" The doctor proclaimed while contorting his face with glee.
But how would you know that, Doctor?
"Oh but that is simple, my dear! Because it is my faavorite form of torture!" And with that he grabbed a huge, rubber hose and shoved it down my throat.
facts -
Water intoxication kills primarily by diluting the blood and causing hyponatraemia (low blood sodium). Water then moves by osmosis from its area of high concentration to its area of low concentration - from the blood to the intracellular space.
The swelling the water causes is called oedema (US - edema), pulmonary oedema in the lungs, cerebral oedema in the brain. Cerebral oedema results in confusion, convulsions, coma and ultimately death.
The figure of 8 gallons/hr is extremely high. The "lethal dose of water" could be very much lower, though I would hesitate to put a figure on it. Leaving wet, dry and secondary drowning aside and considering oral or intravenous fluid, the kidneys of a healthy adult can excrete a maximum of less than 1 litre/hr. This figure may be very much reduced in patients with renal or heart failure in whom fluid balance is notoriously difficult to maintain.
Of course, this does not mean that drinking more than 1 litre/hr will kill you, particularly if you are fluid-depleted. Dehydration is a much more common killer. Homeostasis is quietly effective even in the face of gross physiological insult. Nonetheless, there's a limit.
Drinking large volumes of pure water in a short period, particularly while electrolyte loss is occurring (heavy sweating, bleeding, vomiting, diarrhoea, burns etc.), is dangerous. It remains a major cause of death amongst children worldwide following diarrhoeal illness - though a massive campaign by the UN and WHO has helped. It's what kills people in those inexpressibly stupid water drinking contests. Famously, it's what killed Leah Betts, in whose case excess water consumption was compounded by drug-induced failure of normal homeostasis (see SIADH).
In everyday situations and in normal quantities, pure water is best for rehydration - healthy, readily available and cheap. Dietary sodium intake is almost always more than adequate. When large-volume fluid replacement is required acutely, particularly when electrolytes are being lost (see above), it's often advisable to replace salt and sugar as you go, with isotonic rehydration solutions. You can buy these as sports drinks or sachets of oral rehydration salts. Alternatively you can make your own with 8 level teaspoons of sugar and 1 level teaspoon of salt per litre of water. Half a mashed banana adds flavour and potassium.*
wikipedia on cannabis toxicity and lethal dose
There has never been a documented human fatality from overdosing on marijuana.[11] Information about THC's toxicity is derived from animal studies. The toxicity depends on the route of administration and the laboratory animal. Absorption is limited by serum lipids, which can become saturated with THC, mitigating toxicity.[12] According to the Merck Index, 12th edition, THC has a LD50 (dose killing half of the research subjects) value of 1270 mg/kg (male rats) and 730 mg/kg (female rats) administered orally dissolved in sesame oil.[13] The LD50 value for rats by inhalation of THC is 42 mg/kg of body weight.[13] One estimate of Cannabis's LD50 for humans indicates that about 1500 pounds of marijuana would have to be smoked within 15 minutes.[14] This estimate is supported by studies which indicate that the effective dose of THC is at least 1000 times lower than the estimated lethal dose (a "safety ratio" of 1000:1). This is much higher than alcohol (safety ratio of 10), cocaine (15), or heroin (6).[15]
Animal Administration LD50 [mg/kg]
rat oral 666 [12]
rat (male) oral 1270 [13]
rat (female) oral 730 [13]
rat inhalation 42 [13]
rat intraperitoneal 373 [12]
rat intravenous 29 [12]
mouse intravenous 42 [12]
mouse oral 482 [12]
mouse intraperitoneal 168 [12]
monkey (LDLo) intravenous 128 [12]
dog oral 525 [12]
