Taiwan Data - significance for linear-no-threshold models

[chimericoncogene]

Data from an incident where several thousand Taiwanese were exposed to gamma radiation from Co-60 contaminating the steel used to frame their concrete buildings is presented in the article below.

https://www.nature.com/articles/bjc2017 ... proof=true

Data from about 6,000 subjects exposed over ~10 years at most (?) are presented, with exposures irritatingly categorized into three brackets: 0-5mSv; 5-99mSv, and 100mSv+. No dose rates per year are given.
Rates of leukemia and breast cancer (the latter only in younger women) were found to be elevated (HR 10% or so - a bit high, really, which is suspicious) in the 5-99mSv and 100mSv cohorts, increasing with increasing dose.
The data suggests that a threshold for harmless radiation exposure, if it exists, exists under the 10mSv per year range. The dose estimates are based off a thorough standardized model. There are some issues with effect size, but those are always present.

[Broomstick]

I'd long wondered if there had been any followed up to that Co-60 contamination of structural steel. Although I would have been happier if the results had shown no negative effects I am glad someone has bothered to study this.

Of course, since the exposure was unintentional and for awhile unknown it would be impossible to get really clean data on exact exposure rates. Even so, it does show that the higher the dose the greater the effect which is important information.

Thank you for posting that information and link

[chimericoncogene]

I'd long wondered if there had been any followed up to that Co-60 contamination of structural steel. Although I would have been happier if the results had shown no negative effects I am glad someone has bothered to study this.

Of course, since the exposure was unintentional and for awhile unknown it would be impossible to get really clean data on exact exposure rates. Even so, it does show that the higher the dose the greater the effect which is important information.

As would I, especially since those studies of half a milloon radiation workers didn't yield significant results.

For me, a big question mark is the way-too-large effect sizes detected by the study, and the big error bars in the results. But taken at face value, the Acute myeloid/lymphoid/chronic myeloid leukemia data seem reliable. The fact that the result for all other solid cancers (except breast) is no difference as expected is what makes me more convinced that the effect for leukemia is realish.

Some radiation worker studies have found similar effects, with largish error bars.

https://www.bmj.com/content/351/bmj.h5359

https://www.bmj.com/content/bmj/351/bmj ... height=600

[chimericoncogene]

https://www.ncbi.nlm.nih.gov/pmc/articl ... po=71.0000

If you look at the appendix, the effects start getting apparent at the 200-300mSv occupational exposure mark. That also gives us a threshold under 10mGy excess exposure per year or so, although I may be cherry picking here.

The effect sizes are tiny, and cancer variability is huge. Whether this is an argument against resuming atmospheric nuclear testing (50 mSv to Utah)...

[chimericoncogene]

https://www.ncbi.nlm.nih.gov/books/NBK218130/

An upper bound for this threshold, if it exists (which given that 10mSv a year can be slightly harmful really calls into question, IMO, regardless of comparisons with smog and urban-industrial pollution), can probably be found from thorotrast exposure studies.

Exposure to 6000 mSv a year (!) of thorium alphas in your liver means 1/3 of you get liver cancer in forty years (and that's with cirrhosis due to patchy dead liver tissue!).
Exposure to an average of 2000 mSv a year (!) to your bone marrow starts causing leukemias (just 1% of exposed population of 6000 ppl at 40 years!) at 5 years (typical latency is 2y or so from A-bomb survivors).
So an upper bound to this threshold might be in the range of 50mSv a year for a 100 year lifespan, although given evidence for 2x risk of cataracts (i.e. 5% of population at age 40-50 instead of 2.5%) at 250 mSv it is unlikely to be "very safe".

In theory, if these results are reasonable, you could live in a 1Sv/year post-exchange environment indefinitely without that much of a hassle (would not want to have babies in that, though).

A regulatory limit of 50mSv a year is the upper limit of reasonable, but would permit stress-free atmospheric nuclear testing (yaaay!)

[Elheru Aran]

While this is cool... Is there any reason it's in this forum and not say the science forum?

[chimericoncogene]

While this is cool... Is there any reason it's in this forum and not say the science forum?

Can you move it there? I was initially thinking of this in terms of implications for use of nuclear devices for peaceful applications, which I why I thought of putting in science fiction.

[Bedlam]

I did wonder if the data included the probability of gaining superpowers due to radiation exposure

[LadyTevar]

Off to the Right Forum!

[chimericoncogene]

Thank you LadyTrevar.

With the Taiwan data and the general state of the field, 50mSv/year would be a little scary. Definitely an upper limit of reasonable. Over a 100 year lifespan, you're soaking up 5000mSv of radiation; if LNT (10% risk per Sv, no matter how trickle charged) ends up being the correct model, you're causing a 50% absolute increase in cancer incidence. So worst case scenario 80% of the population gets cancer instead of 33% as is currently the case. A lot of people survive cancer, maybe 1/3 die, but still the potential aggregate effects may be large. WHICH IS MORE THAN A LITTLE CONCERNING, which is pretty much why they set the limit so darned low (1mSv a year - about 1/5-1/10 of natural exposure) once they adopted LNT.

Such large cumulative doses to large numbers of people have been tested only in the radon areas and some of the small powerplant studies (seriously, the overwhelming majority of powerplant workers mostly have normal radiation exposure because safety precautions are taken), but radon apparently is less carcinogenic than expected, as seen from the thorotrast study. Not that many lung cancers even when they had thorium leaking radon inside people.

The good news is unless you're fracking natural gas, mining hard minerals, digging canals (esp. this one - nuclear earthmoving is relatively dirty), and cracking shale in situ with thermonuclear bombs in a very cavalier and irresponsible manner, you aren't likely to need a 50mSv per year limit. But if you are, you will need that limit or you really can't justify to the people of Nicaragua how you're going to blast that sea-level canal through their country.