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?

  • RightHandOfIkaros@lemmy.worldEnglish
    33·
    5 months ago

    “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.worldOP
      9·
      5 months ago

      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?

      • Ephera@lemmy.ml
        10·
        5 months ago

        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
          6·
          5 months ago

          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

          • Ephera@lemmy.ml
            1·
            5 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…

      • RegalPotoo@lemmy.worldEnglish
        3·
        5 months ago

        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.

  • AmidFuror@fedia.io
    161·
    5 months ago

    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.

      • antlion@lemmy.dbzer0.com
        1·
        5 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”.

  • Paragone@lemmy.world
    41·
    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 )