3 ms·

I can’t recall the name of the principle, or the exact dose, but isn’t 1 Sv enough to cause a 50% death probability from radiation sickness, and 3 Sv enough to

I can’t recall the name of the principle, or the exact dose, but isn’t 1 Sv enough to cause a 50% death probability from radiation sickness, and 3 Sv enough to cause a cancer? There is a good youtube series (IIRC nuclear policy course at MIT) I was watching when the Chernobyl show was on last year. So 0.25 mSv is enough to cause a cancer for every 12,000 people they scan. That’s a lot of people considering the throughput of airports. Lovely. I’m glad this was shit-canned.

vkou 6y ago
You have 4 litres of blood in your body. You will die if you lose 2 of them. A typical lab blood draw is ~10 ml. Does this mean that for every two hundred people who get their blood drawn, one is killed?
- acidburnNSA 6y ago
  This is a great example of the ridiculousness of linear no threshold models.
- madengr 6y ago
  Of course not, but if I inject you with 2 L of peanut oil, it will kill you. If I do the same at 1 ml to 2000 people, maybe the statistics work out so a single, hyper-allergic person is dead. That’s all the linear approximation is saying, and that lecture series says it has held true. The interesting thing about it, is the dose for a single cancer is above the lethal dosage.
acidburnNSA 6y ago
The LD50/30 acute dose of ionizing radiation is around 4000 mSv (4 Sv). You're assuming a linear no-threshold dose response for ionizing radiation, which is indeed what radiation people have used since the 1950s when we didn't have enough data to be less conservative. In the US, natural background dose averages around 3 mSv/year. Some places in the world have high backgrounds, in the 30-100 mSv/year range. Even there we have not seen a clear negative (or positive) response.
- hammock 6y ago
  I get the point about linear no threshold, but I don't get the point of bringing up background dose. If there is a threshold, then acute doses are worse than cumulative right? Taking even your highest figure 100msv, that's over an entire year. In a 5 sec span, that would be 0.0000159 msv, or 200,000x less than the 3msv from the machine in 5 sec (or less).
  - acidburnNSA 6y ago
    Acute high-dose is indeed worse than cumulative. Less than 100 mSv acute has never been shown to cause (or not cause) harm or benefit. I bring up background just to point out that radiation is very natural and our bodies evolved in a radioactive world and have repair mechanisms that appear to be totally capable of handling low doses relevant to these machines. I can see that that's confusing to a degree. I may be mistaken, I believe you're confusing milli-Sieverts (mSv) with micro-Sieverts (μSv). The machines are spec'd at 0.25 μSv/scan, or 0.00025 mSv.

vkou 6y ago

You have 4 litres of blood in your body. You will die if you lose 2 of them. A typical lab blood draw is ~10 ml. Does this mean that for every two hundred people who get their blood drawn, one is killed?

acidburnNSA 6y ago
This is a great example of the ridiculousness of linear no threshold models.
madengr 6y ago
Of course not, but if I inject you with 2 L of peanut oil, it will kill you. If I do the same at 1 ml to 2000 people, maybe the statistics work out so a single, hyper-allergic person is dead. That’s all the linear approximation is saying, and that lecture series says it has held true. The interesting thing about it, is the dose for a single cancer is above the lethal dosage.

acidburnNSA 6y ago

The LD50/30 acute dose of ionizing radiation is around 4000 mSv (4 Sv). You're assuming a linear no-threshold dose response for ionizing radiation, which is indeed what radiation people have used since the 1950s when we didn't have enough data to be less conservative. In the US, natural background dose averages around 3 mSv/year. Some places in the world have high backgrounds, in the 30-100 mSv/year range. Even there we have not seen a clear negative (or positive) response.

hammock 6y ago
I get the point about linear no threshold, but I don't get the point of bringing up background dose. If there is a threshold, then acute doses are worse than cumulative right? Taking even your highest figure 100msv, that's over an entire year. In a 5 sec span, that would be 0.0000159 msv, or 200,000x less than the 3msv from the machine in 5 sec (or less).
- acidburnNSA 6y ago
  Acute high-dose is indeed worse than cumulative. Less than 100 mSv acute has never been shown to cause (or not cause) harm or benefit. I bring up background just to point out that radiation is very natural and our bodies evolved in a radioactive world and have repair mechanisms that appear to be totally capable of handling low doses relevant to these machines. I can see that that's confusing to a degree. I may be mistaken, I believe you're confusing milli-Sieverts (mSv) with micro-Sieverts (μSv). The machines are spec'd at 0.25 μSv/scan, or 0.00025 mSv.