Uranium in Drinking Water?

Your student is right to be worried about uranium in drinking water. The issue is not radioactivity but heavy metal toxicity. I don't know the precise amounts, as it's not my field. However, I know that uranium's close chemical relative plutonium is among the most toxic substances known to man--even though it is much more radioactive than uranium, it's still the heavy metal toxicity that would kill you. For plutonium, a few milligrams is plenty. It probably takes a bit more uranium than that, but the question is worth asking.

For U, 30 micrograms/liter. See the EPA page for more info.

I'd be much more concerned about the radon. It's heavier than air, so depending how well ventilated your student's house is, it can build up inside and significantly increase the risk of lung cancer. See http://www.epa.gov/radon/pubs/citguide.html

The EPA has a whole page on the matter: see http://www.epa.gov/rpdweb00/radionuclides/uranium.html

"The uranium limit is 30 µg/l (micrograms per liter) in drinking water."

Natural uranium isn't terribly radioactive (i.e. it has a long half-life), although it is an alpha-emitter which means you really don't want any inside you unless you really enjoy having your innards ionized by helium nuclei.

My ancient copy of Lamarsh's "Introduction to Nuclear Engineering" doesn't cover biological uptake of uranium so I'm going to make the wild guess that chemical toxicity is more important than radiological effects where health effects are concerned; see http://www.fas.org/nuke/guide/usa/doctrine/dod/5100-52m/chap9.pdf

The average annual amount of uranium ingested is ~0.14mCi, mostly via food, not drinking water. There's more trace uranium in phosphate fertilizer than in drinking water so consequently most uranium is ingested by eating, not drinking. It tends to hurt the kidneys more than anything. See chapter 6 in BEIR-IV - it's fairly recent and has more chemical info than you probably care about but it should tell you what you want to know.

However, I know that uranium's close chemical relative plutonium is among the most toxic substances known to man--even though it is much more radioactive than uranium, it's still the heavy metal toxicity that would kill you.

I don't think so -- the problem is that the body will use plutonium in place of other metals in the body, where the radioactive decay causes Bad Things from close-up. Same problem with strontium-90.

U-238 is just a nasty heavy metal, with some minor added ugliness from the low-level radioactivity. IIRC, potassium is not much safer on the radiation side.

The question is difficult to give a single answer to because it's sort of wrong. Are we talking immediate effects, or long term effects? Dismissing radon for long term effects strikes me as interesting, to say the least. Are we talking morbidity AND mortality?

For what it's worth, I DO consider the chemical toxicity of uranium a major issue, at least for deterministic effects.

Then you have to consider stochastic effects...

Anyhow, it's not as obvious or trivial as some of the comments may suggest. WHO, the EPA, Health Canada, the NRC, Australia etc all have guideline values you can refer to and then examine the methodology/assumptions/DCFs/pathways to see if it's acceptable for your purposes.

Get a tap water filtration cartridge, and replace it regularly because this is a potential hazard. The EPA standards are based on animal studies but there are now human study data that suggest the EPA uranium limits are too high and not very safe over a long period of time.

(Radon accumulation is a non-issue here. People got harmed by radon inhalation by 1) working in uranium mines 2) living in houses built from uranium ore tails or cinder-blocks that contained coal ash high in uranium).

U causes cumulative kidney damage. Its radiotoxicity is low but the chemical toxicity is comparable to hexavalent chromium (Erin Bronkovic fame). There are additional kinds of problems related to inhaled uranium - nosebleeds and lung inflammation, rashes and persistent fatigue - but those do not apply here.

There was an outbreak of severe uranium poisoning in Iraq after looters raided Saddam's storage of yellowcake at al-Tuwaitha, dumped the contents and sold the drums on the market. People were using them as containers for milk and rain water

More info here: http://www.wise-uranium.org/utox.html

I'm not conducting a DCA here, though I've certainly done that.

Instead I'll ask the type of question you should when getting answers like those provided by, say, milkshake -- why is the radiological-based ALI for the uranium with progeny 10 times lower than uranium alone (making it comparable with the chemical toxicity based ALIs) on the link you provide?

Also, in what scenario would you imagine radon and uranium could be an ingestion pathway threat (presumably via groundwater) and yet not be concerned with radon and daughter product inhalation pathways (no basement or airtight basement?).

Finally, what is the effectiveness of your countermeasures/protective actions?

Eric @1 offers: I don't know the precise amounts, as it's not my field. However, I know that uranium's close chemical relative plutonium is among the most toxic substances known to man ...

Why didn't you stop with "I don't know what I am talking about" and leave it at that?

Plutonium and Uranium uptake has been studied extensively, although the data set for the former is quite limited because the occupational limits for Pu were set before any industrial work with it, based on analogies to Radium. One thing stands out: eating Pu is not the same as breathing it, because the GI tract doesn't see it as food - although uptake depends on the chemical form it is in. IIRC, the workplace studies worried most about metallic forms. As noted above, most of the concern about U has shifted to its chemical rather than radiological properties. I'd also worry about what other metals are in the water.

I would only be concerned about Radon if it shows up in the air in your house. However, the health studies of high residential Rn areas (not to be confused with mines) have, as often as not, shown a decrease in cancer rates. The reason remains a puzzle, AFAIK. (Lest you ask, they did control for smoking in all of those studies.)

CCPhysicist says:

eating Pu is not the same as breathing it

Priceless. The 5-year-old in me hasn't stopped laughing.

Here's a nice technical document on uranium in drinking water (a few years old now, but still nice): http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/uranium/index-eng.php

And here's a slightly less technical one on radon in water: http://www.hc-sc.gc.ca/ewh-semt/pubs/water-eau/radon/index-eng.php

(note that "Individuals who attempt to remove radon from their water supply using point-of-use devices containing activated carbon should be cautioned regarding the difficulties of disposing of the used radioactive carbon.")

Radon in air, for completeness: http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/environ/radon-eng.php

A recent 'heavy metal challenge' (CaEDTA) found me elevated in Uranium (0.09 vice a ref. rge < 0.03 ug). Is there any place where one can find surveys of U content in groundwater supplies? My suspicions about source include the shallow well I drank from for 4 years - through a water ionizer that had its own RO filtration. A year ago, when I moved into the Virginia countryside, and a drilled well, I had the water analyzed by National Testing Labrotories of Cleveland, OH. That test did not include U among its metals, but I had no Uranium concerns at that time. My other suspicion is a partial plate with 3 teeth that are > 40 yrs. old, but 2 teeth replaced about 3 yrs. ago. I don't know how promiscuously dental labs have used U to enhance tooth flourescence. Nor do I know how leachable such a U source might be. Any thoughts out there? Anyone know of a testing lab that will specifically test for U?

By the way there are a stretch of Uranium mining leases that cut across Virginia about 30-35 miles upland from the 2 cities that I have occupied. Althoug some VA Tech scientists believe these deposits have formed in a stable reservoir in their unpermeable phosphate-rich beds, I still have to wonder about mild leaching into ground water and aquifers.