(13) Workers at Nuclear Waste Site in New Mexico Inhaled Radioactive Materials

[kristopher]

Workers at Nuclear Waste Site in New Mexico Inhaled Radioactive Materials
By MATTHEW L. WALDFEB. 27, 2014


WASHINGTON — Thirteen employees who worked the night shift at a nuclear waste burial site in New Mexico after an underground leak are carrying radioactive materials in their bodies, but it is too soon to say how much health risk this poses, Energy Department officials said on Thursday.

The workers inhaled plutonium and americium, which if lodged in the body bombards internal organs with subatomic particles for the rest of the person’s lifetime. The dose calculation is a bit arcane because the dose in such cases will be delivered over many years.

Calculating a lifetime dose will require several urine and fecal samples, taken over time, to determine the rate at which the body is eliminating the materials, said Joe Franco, manager of the Energy Department’s Carlsbad, N.M., field office, which oversees operations at the Waste Isolation Pilot Plant, where bomb wastes are buried in an ancient salt bed deep beneath the desert.

“Right now we have one single data point; there was one reading,” Mr. Franco said at a news conference in Carlsbad, explaining that more readings were necessary. Sensors in the salt mine detected a leak at about 11:30 p.m. on Feb. 14. At that hour, no one was in the mine, and automatic systems reduced the ventilation and ran the exhaust through high efficiency particulate filters, officials said, minimizing the flow of materials to the surface.

The next morning, after officials realized that the surface was contaminated...

http://www.nytimes.com/2014/02/28/us/workers-at-nuclear-waste-site-in-new-mexico-inhaled-radioactive-materials.html

[Demeter]

1. Just lovely

Pray for them, because modern medicine has no answer.

[LiberalEsto]

2. Makes me think of Karen Silkwood.

May she rest in peace.

[NMDemDist2]

3. since i live very close to there, i have been keeping a VERY close eye on the situation

the workers got a tiny dose, much less than a chest e-ray. WIPP has a policy 'anything over a zero reading is too much'

it's a great philosophy, but it makes the headlines sound much worse than it is

[madokie]

4. Any ratioactive particle in the lungs is not good

Especially if its plutonium
I don't think the headlines is over stating the dangers here at all.

http://enenews.com/us-official-large-amounts-radioactive-particles-were-released-during-puff-at-leaking-nuclear-site-expert-plutonium-and-americium-can-travel-a-long-way-in-wind-tv-reporter-they

[kristopher]

5. Well, dosing in this case isn't a one time and it's gone event.

Also the proximity of the particles to cell tissue is a factor that makes the X-ray comparison questionable without knowing a bit more about who is making that assessment.

Why does it make no sense to compare in-flight radiation exposure and ingesting radioactive isotopes? It is wrong to compare internal emitters with external emitters, ie, ingesting radioactive isotopes versus in-flight exposure or background radiation. It is like comparing warming oneself near a fire versus eating a red hot coal. Physicians for Social Responsibility in the United States recently issued a statement asserting “there is no safe level of radionuclide exposure, whether from food, water or other sources. Period.” There are a number of different types of radiation, including cosmic radiation from space, terrestrial radiation which is emitted by radioactive elements in the ground, and man-made radiation such as that released by the detonation of an atomic bomb or by nuclear reactors in meltdown....

More here:
http://www.mi2g.com/cgi/mi2g/frameset.php?pageid=http%3A//www.mi2g.com/cgi/mi2g/press/060411.php

[caraher]

6. Some specifics for plutonium and americium

Argonne National Lab has some handy fact sheets that are a good starting place for figuring out what a given radionuclide does in the body (I just Google "Argonne fact sheet <element>" to find them).

From the plutonium fact sheet:

When plutonium is inhaled, a significant fraction can move from the lungs through the blood to other organs, depending on the solubility of the compound.... After leaving the intestine or lung, about 10% clears the body. The rest of what enters the bloodstream deposits about equally in the liver and skeleton where it remains for long periods of time, with biological retention half-lives of about 20 and 50 years, respectively, per simplified models that do not reflect intermediate redistribution. The amount deposited in the liver and skeleton depends on the age of the individual, with fractional uptake in the liver increasing with age. Plutonium in the skeleton deposits on the cortical and trabecular surfaces of bones and slowly redistributes throughout the volume of mineral bone with time.

So about 90% of inhaled plutonium typically remains in the body for decades. Estimating health risks requires knowing the amount inhaled; the fact sheet gives two different ways of looking at the risk. They report a lifetime excess cancer mortality risk of about 3 x 10^(-8) per picocurie for inhalation exposure. They also say, "...for inhalation (the exposure of highest risk), breathing in 5,000 respirable plutonium particles of about 3 microns each is estimated to increase an individual’s risk of incurring a fatal cancer about 1% above the U.S. average."

From the americium fact sheet:

After ingestion or inhalation, most americium is excreted from the body within a few days and never enters the bloodstream; only about 0.05% of the amount taken into the body by ingestion is absorbed into the blood. After leaving the intestine or lung, about 10% clears the body. The rest of what enters the bloodstream deposits about equally in the liver and skeleton where it remains for long periods of time, with biological retention half-lives of about 20 and 50 years, respectively (per simplified models that do not reflect intermediate redistribution). The amount deposited in the liver and skeleton depends on the age of the individual, with fractional uptake in the liver increasing with age. Americium in the skeleton is deposited uniformly on cortical and trabecular surfaces of bones and slowly redistributes throughout the volume of mineral bone over time.

So very little americium is absorbed; but what does remain stays for a long time, very much the way plutonium does. The excess cancer mortality risk per picocurie is comparable to, but smaller than, the values for plutonium. But it appears that, per atom, plutonum is a bigger concern because a larger fraction of it stays in the body.

It's worth noting that these biological profiles are very different from the contaminants most prevalent in reactor accidents like Cs-137, which has a biological half-life of a few months rather than decades.

[kristopher]

7. Thanks.

Would you know how accurately they are able estimate the quantity of respirable particles and what the most reliable methods for measuring it are? I'm guessing that the conditions described mean they are dealing with open air exposure that wasn't expected to be there, so...?

[Yo_Mama]

8. One way is by measuring the excretion rate and change in time.

So they can sample the urine several times, and then you can work back to an estimate of original exposure.

[caraher]

9. At this stage such an estimate would be challenging

I think Yo_Mama has it right - the best way to figure out exposure is ongoing monitoring of the sort described. I'd imagine there will always be pretty big uncertainties associated with any such measurement - you can probably get the order of magnitude right, but since there's also a lot of uncertainty associated with the risk even given accurate exposure data, it's not really necessary to do much better to decide whether doing more than monitoring is warranted.