Comment by acidburnNSA | Hacker News Reader

Comment by acidburnNSA | Hacker News Reader

With radiation, I always recommend people study page 6 of this DOE radiation dose range pdf [1] to put dose rates in context. The spectrum of radiation doses spans many orders of magnitude and a single atom decaying is readily detectable.

Note in particular that there are places on Earth like Ramsar, Iran that have natural background dose rates above 50 mSv/year and no one has been able to show definitively that dose rates at or below that level do or do not cause harm (or benefit!).

[1] https://www.energy.gov/sites/prod/files/2018/01/f46/doe-ioni...

Another fun data point is the longitudinal studies of flight crew who spend a good part of their career exposed to higher-than-normal natural cosmic radiation (while flying they are above much of the Earth's protective atmosphere) [2]. We should compare how much dose we get from the scanners at airports to how much we get from intergalactic protons raining down from the cosmos while we're up in the air.

[2] https://www.bmj.com/content/325/7364/567

One time I took a geiger counter on a flight just for fun [3]. It really was clickin'!

[3] https://whatisnuclear.com/blog/2014-05-17-radiation-on-fligh...

I don't get why a full year's worth of background radiation is always compared to an acute 5-sec (or less) exposure from an x-ray machine.

If the background rate is 50msv/year, and a machine doses that much (50msv) in 5 seconds, that's 6.3 MILLION TIMES greater than the background dose.

This is an excellent point, does an acute dose of radiation in a short timespan cause more cellular damage than long-term exposure?

Absolutely yes. But acute low-dose below 100,000 μSv has never been shown to cause or not cause harm.

Using uniform units, 0.25 μSv acute dose is what the manufacturers claim for these devices. Annual average background from all sources in US (including these) 6,000 μSv/yr. So you need a scan every 21 minutes for a year to roughly double your annual dose. In some parts of the world, the natural background rate is higher. Like 50,000 μSv/yr. Cancers or other harm have never been shown to occur (or not occur) below acute or annual doses of about 100,000 μSv.

So you need 400,000 of these scans (at the manufactuer-claimed dose of μSv) to reach a dose that is thought to have an above-zero increase cancer risk.

You're not grasping the biology. Damage repair mechanisms have a capacity limit that itself varies with exposure. In particular it's been shown that acute dosage timing of multiple exposures is different than continuous exposure with the same integrated dose.

I will strengthen my statement. Acute doses below 100 mSv have never been conclusively shown to cause or not cause harm or benefit. Certainly annual doses at that level also have not.

The LD50/30 acute dose of radiation is 4,000 mSv. See chart I linked above.

Certainly acute high doses are worse than the same dose spread over years or decades. I learned that in nuclear engineering school 20 years ago. Please don't assume I'm not grasping it.

> I don't get why a full year's worth of background radiation is always compared to an acute 5-sec (or less) exposure from an x-ray machine.

Usually because we don't have as much data on acute exposures. The best are from Chernobyl and the atomic bombs (tests and weapons). The issue with these is that we're talking about dosages that are MUCH higher. You'll also find plenty of studies with pilots (and even mechanics), medical staff, and dentists but if you read into the reports you'll see that there are a lot of factors involved that make it difficult to call radiation the culprit, specifically because these groups are exposed to a lot of other known carcinogens and are likely to be tested more frequently (pilots get frequent medicals and doctors are.... well... you know... doctors). So pretty much no matter what you do, there aren't great comparisons and noway to completely isolate just radiation.

Edit: it is hard to get this data because it is unethical to just expose people to radiation and see at what levels they die at. Plus, such a study would take decades

For a longer term study of the measured cosmic radiation exposure rates that one could expect from commercial flights I have followed this study:

https://spaceweather.com/

They also regularly launch balloons to track atmospheric changes. This is a long-running experiment with data gathered by high school kids. Pretty awesome. You can sponsor a flight and get a token item that has traveled to the edge of space in exchange. Great website.

To estimate the exposure of real flights there is also the "EPCARD ONLINE Flight Dosimetry for Aviation Personel" online calculator[1]. It is provided by a member of the Helmholtz Association, which is the largest scientific organization in Germany, so it should be credible.

[1] https://www1.helmholtz-muenchen.de/epcard/online/fluginput.p...

This is another good chart:

https://xkcd.com/radiation/

This is the chart I always use when my friends start getting uppity about radiation.

It is being proven that 100msv radiation was directly linked with cancer comes from data from Chernobyl, so 50msv I'd still being concerned this is like having 500k X-ray scan at one take, the greter rist doesn't come from the high dose itself, if comes from a time factor, the question needs to be, in how much time you get 50msv? It you tell me in one day I'll very concerned, this is a very high dose for rapidly changing organs like the bone marrow to absorb in one take (causing caners like leukemia ...)

https://xkcd.com/radiation/

Not sure what you're referring to from Chernobyl. The UN team of scientists on radiation (akin to the IPCC for climate change) has this to say about Chernoby: https://www.unscear.org/unscear/en/chernobyl.html

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