"A lethal dose of one point three to two point one (or one and three tenths to two and one tenth) nanograms per kilogram in humans."
So are they saying nanograms of the stuff per kilograms of the human?
In other words are they saying it's a ratio compared to the weight of the person?
That is correct. The ratio is nanograms of substance to kilograms of bodyweight
Thank you
Yeah, personally I would say that it's per kg bodyweight.
But I would also do my darndest to try write it, since "ng/kg" is kind of just nonsense. It makes it look like you could divide the grams out of that to get a fixed ratio, which is not correct at all.
But it is a fixed ratio.
If it was in pounds, metric tons, moles or atomic mass units... It doesn't change the ratio, the actual number.
Would it be acceptable to drop the unit all together?
"Lethal dose is 0.000000012 : 1 (substance : bodyweight)" (I made up the number).
I'm not sure if there is a better way of writing the ratio.
Could a fraction be more applicable?
"lethal dose is 1/600000 of bodyweight"
I'm sure it's written as ng/kg to show the base units are the same, and the rest is just "fiddling" scientific notation
moles
would not work, as they are no mass unit. 1 mol of Botox does not have the same weight as 1 mol of human (If that is defined at all, as organisms are no pure substances).
Ah, yes good point
Well, what I meant with that, is that it's semantically important that it's ng of the substance per kg bodyweight.
If it was ng of the substance per kg of the substance, then in proper mathematical physics, the unit would disappear completely.
So, for example:
42000000000 ng of the substance / kg of the substance
Is equivalent to:
42000000000 * 0.000000001 * kg of the substance / kg of the substance
Which means in the end, you just have: 42
As my physics teacher would often say: Is that 42 potatoes or sausages or what is it?
A number without a unit is just devoid of meaning...
Thank you
Yeah - the dose is the poison (if you drink enough water it becomes toxic), so if you are talking precisely you need to describe the concentration of a substance in which it is likely lethal to a person, and that's typically expressed as mass of a substance per mass of bodyweight. A lot of the time you will also see this expressed as an "LD50" value; the dose at which you'd expect 50% of people to die. This accounts for the fact that people's metabolisms vary quite widely.
~1ng/kg ~= 0.08ug for a typical (~80kg) person, which is a very tiny amount - whatever you are talking about is incredibly toxic.
A quick Google of the numbers says OP is likely talking about botulism so I guess they perhaps have been reading about Botox
LD50 is per kg of rat by weight
You can say "nanograms per kilogram." You could shorten it to "nanograms per kilo."
If it were mg/kg, you could say "migs per kig." You won't trick me into saying the equivalent for nanograms, though.
Edit: Not sure what you mean by how to write it as a decimal number. It's 0.0000000021g per kg. It wouldn't be standard to give just a ratio of like mass to mass because as others have written it is mass of substance vs mass of patient.
What's wrong with nags? Isn't that a term for a rundown horse or something?
2.1 ppt (parts per trillion)
That assumes that the particles are the same mass for the drug and human.
You could say a small percent mass.
Yeah it’s typically not used for dosages, rather it’s for concentrations in solution. However strictly speaking the grams cancel in the units of ng/kg and you are left with ppt. I think of ppm and ppt as very small percentages anyway. As per cent means part per one hundred. Can’t use “permille” because it means part per thousand but sounds like part per million.
In the case of a lethal dose, I think it would be fine to say, “it’s lethal at a rate of 2 trillionths of body mass”.
Seriously?
Damn!
Lots of good responses so far.
0.0000000021g/kg
or 0.0000000000021kg/kg, if you wanted the same units both sides..
( I'm presuming this was your last-line's request )
Fentanyl?
Way worse Clostridium botulinum
Most potent toxin known to science
Most potent toxin known to science
...so far.
That's true, I have been wrong on my natural gas.
Hell yeah. I know that one. Hold on, I'm gonna inject a very small portion of that into my face. Now you know I'm happy.
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