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Posted By Chris Knagg
Could someone offer me a plain english explanation to LD50, or tell me where I could find an explanation of LD50.
Thankyou
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Posted By Juliet Fennell
My understanding is that LD 50 refers to the lethal dose administered to test subjects (usually mice or rats) in which 50% of the subjects died when the level stated was administered. The material safety data sheet on the product should state what animal the product was tested on. I hope this helps. Juliet
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Posted By Neil Budworth
The LD50s are often used as part of the labelling criteria for hazardous chemicals, certain key value LD50s will trigger, harmful, toxic and very toxic labels.
There is also an equivalent for gases and for substances in water etc the LC50 Lethal Concentration 50% again these are used to as part of the classifictaion process.
Drop me a line if I can be of any more help
Best Regards
Neil
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Posted By Jay Joshi
LD50--Lethal Dose Fifty--is a calculated dose of a material that is expected to cause the death of 50% of an entire defined experimental animal population. It is determined from the exposure to the material, by any route other than inhalation, of a significant number from that population. Other lethal dose percentages, such as LD1, LD10, LD30, and LD99, may be published in the scientific literature for the specific purposes of the author. Such data would be published if these figures, in the absence of a calculated lethal dose (LD50), were the lowest found in the literature---
LC50--Lethal Concentration Fifty --a calculated concentration of a material in air, exposure to which for a specified length of time is expected to cause the death of 50% of an entire defined experimental animal population. It is determined from the exposure to the material of a significant number from that population.
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Posted By Nancy Lett
What our colleagues say is fine, but the conclusions drawn from LD50, etc., rates are challengeable. EH40 threshold limits are often based on a 'totting up' process. The lethal concentration is increased in line with the body weight of the average human being, and an assumed 'LD' is calculated.
There are problems with the assumtion in that there is not necessarily any corrolation in this generalism, nor is there much resemblance in the physiology of a rat (the most commonly used animal)and a human!
It's still the best we've got in many instances, so it's better than nothing, but please treat the assumtion with caution.
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Posted By Merv Newman
all the previous technical replies are correct, but still leave LD50 a bit hard to grasp - why does it kill only 50% and not the others ?
Simply because an animals resistance to sustances varies, assumed to be a normal distribution.
If an LD50 is 1gr/Kg of body weight, some stonger, fitter more resistant animals might be able to absorb much more without dying. Others might be killed by just half as much.
So the LD50 is just saying that, on average, 50% of the animals will be killed by a dose of 1 gr per Kg
I hope you didn't really need that explanation
Merv Newman
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Posted By David J Bristow
Chris
LD50 = Lethal Dose 50
As far as my memory serves me, LD50 is a term given to the testing of a "substances" on 50 animals - they could be rabbits, rats,mice etc, etc.
The 50 animals are subjected to a dose of a chemical and after a given period of time the number of animals that surfive (from the origial 50), or not as the case may, will indicate the "Lethal dose" of the given chemical.
I hope this information is of use
Regards
David B
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Posted By Adrian Watson
Dear David,
I'm sorry to have to correct you. The LD50 is the dose that kills 50 percent of a test population. The number of test animals varies according to the test protacol but normally varies between 30 and 100 test animals.
Whilst the LD50 is a useful starting point, there are a number of problems with its use as stated in the discussion. These include that it does not give an indication of intra and inter species toxicity. Furthermore it also does not indicate the shape of the toxicity curve. A substance with a shallow curve allows a greater degree of safety rather than a steep curve which goes from safe to dangerous doses over a smaller scale.
Further details are given in good toxicity textbooks such as Principles of toxicity Williams, James and Roberts.
Regards
Adrian Watson MSc Dip Occ Hyg
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Posted By David J Bristow
Reply to Adrian Watson
I stand corrected Arian,thank you for your comments.
Regards
David B
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