this post was submitted on 11 Jun 2024
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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?

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[–] RightHandOfIkaros@lemmy.world 44 points 5 months ago (1 children)

"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."

[–] andrewta@lemmy.world 12 points 5 months ago (3 children)

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?

[–] ZapBeebz_@lemmy.world 25 points 5 months ago (1 children)

That is correct. The ratio is nanograms of substance to kilograms of bodyweight

[–] andrewta@lemmy.world 5 points 5 months ago
[–] Ephera@lemmy.ml 12 points 5 months ago (2 children)

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.

[–] towerful@programming.dev 8 points 5 months ago (2 children)

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

[–] Successful_Try543@feddit.de 6 points 5 months ago* (last edited 5 months ago) (1 children)

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).

[–] towerful@programming.dev 3 points 5 months ago

Ah, yes good point

[–] Ephera@lemmy.ml 1 points 4 months ago

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...

[–] andrewta@lemmy.world 4 points 5 months ago
[–] RegalPotoo@lemmy.world 4 points 5 months ago (3 children)

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.

[–] 9point6@lemmy.world 4 points 5 months ago (1 children)

A quick Google of the numbers says OP is likely talking about botulism so I guess they perhaps have been reading about Botox

[–] andrewta@lemmy.world 3 points 5 months ago

Close was talking about Clostridium botulinum

Botulinium

[–] andrewta@lemmy.world 2 points 5 months ago
[–] Raffster@lemmy.world 1 points 4 months ago

LD50 is per kg of rat by weight

[–] AmidFuror@fedia.io 19 points 5 months ago* (last edited 5 months ago) (1 children)

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.

[–] Zorque@lemmy.world 9 points 5 months ago (1 children)

What's wrong with nags? Isn't that a term for a rundown horse or something?

[–] antlion@lemmy.dbzer0.com 9 points 5 months ago (2 children)

2.1 ppt (parts per trillion)

[–] PedanticPanda@lemmy.world 3 points 5 months ago (1 children)

That assumes that the particles are the same mass for the drug and human.

You could say a small percent mass.

[–] antlion@lemmy.dbzer0.com 1 points 4 months ago

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”.

[–] andrewta@lemmy.world 2 points 5 months ago

Seriously?

Damn!

Lots of good responses so far.

[–] Paragone@lemmy.world 4 points 5 months ago

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 )

[–] Crackhappy@lemmy.world -1 points 5 months ago (1 children)
[–] andrewta@lemmy.world 8 points 5 months ago* (last edited 5 months ago) (2 children)

Way worse Clostridium botulinum

Most potent toxin known to science

[–] listless@lemmy.cringecollective.io 5 points 5 months ago (1 children)

Most potent toxin known to science

...so far.

[–] andrewta@lemmy.world 2 points 5 months ago

That's true, I have been wrong on my natural gas.

[–] Crackhappy@lemmy.world 4 points 5 months ago

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.