I know the ng means nanogram
But I’m curious how would I say the above line of 2.1 ng/kg
For context I got it from this paragraph
a lethal dose of 1.3–2.1 ng/kg in humans
Would it be
2.1 nanogram per kilogram?
Also if I wanted to write that as a decimal number how would i write that?
“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/kgto show the base units are the same, and the rest is just “fiddling” scientific notationwould 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 substanceperkg bodyweight.If it was
ng of the substanceperkg of the substance, then in proper mathematical physics, the unit would disappear completely.So, for example:
42000000000
ng of the substance/kg of the substanceIs equivalent to:
42000000000 * 0.000000001 *
kg of the substance/kg of the substanceWhich 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
Close was talking about Clostridium botulinum
Botulinium
Thank you
Botulinum
LD50 is per kg of rat by weight