Sunday, 2 October 2011

Radioactive Drinking Water - erk!

(Texas, USA)
People talking about radiation contamination need to be more careful - misuse of the terms makes it difficult to reality check the stories. I saw this with Fukushima reporting and it is in a lot of news and blog reports on the Texas water scare too.

Lets be clear: the water is contaminated with radium, which is a metal, probably in the form of radium-chloride, which is radioactive in the sense that it emits ionizing radiation. It is not "contaminated by radiation". The water there has always been contaminated like this.

Not all radiation is a problem and radium is not one of the worst - though it is very radioactive. It is a 5-6MeV alpha emmitter. Alpha particles have a large mass and charge so they don't go fast and don't penetrate all that much - seldom getting through your skin. 1g of radium has an activity of 1Cu (1 Curie)- the tanks and pipes test to 15-20pCu/l (1 picoCurie is 1x10-12 or 0.000000000001 Curies). Doesn't sound like a lot? It's 3-4 times the Federal EPA safety limit... but is that a lot? We'll see.

Pipes become radioactive because of radium in calcium deposits that build up over time... y'know: lime buildup and that sort of thing? The water does not become radioactive from passing through radioactive pipes but by dissolving some of the radium and carrying it along.

The big probem is when you get it in your body. There it replaces calcium (weakening bones and teeth) and accumulates. Radium decay products are also poisonous, and radioactive. On top of which, you have the radiation damage. Alphas are very damaging inside the body - outside they don't much get through you skin. This is why the presence of dissolved radium salts in drinking water is very serious.

The regions effected have been radioactive basically for ever. The radium comes from Uranium-rich rocks and dirt deposited there when the Earth was younger. It got picked up when the EPA standard changed and officials decided to do a re-check: it seems it got tougher. So how are we supposed to figure out what this means?

In 1944 the, the Manhatten Project set the human tolerance dose at one 1μg (total) ingested... or 1μCu of activity. After that you had to stop working with radioactive stuff. That's smaller than a speck of dust so if you walked into a cloud of radium dust and breathed in you are basically dead meat, but the Texans are drinking it, not inhaling it. In much much smaller doses. So it will take a bit longer to build up in their bodies. How long?

To ingest that much in Texas, you need to drink 50,000l of water from the most contaminated sites. If you drink the popular 2l a day it would take around 70 years to get this high (assuming steady consumption and 100% of the radium is retained.)

Of course, things have changed a bit since the Manhatten Project. We understand more about radiation now. It's more dangerous than they thought. From the above you can see why the EPA safe doses are what they are: there is no way, at those levels, of getting a health-threatening dose in your lifetime. Even if we halve the tolerance level, you still have 35 years to build it up. You can also see why the EPA and State people have not exactly been clamoring to tell everyone.

Has anyone done a review of health effects from such long exposure?  I can't tell. The few papers I've read (see the links on this page) haven't told me. But it's been like this for generations. The lime buildup could be more recent, but we are still talking geological time! This translates to at least decades of exposure at best. So you'd expect the leukemia and cancer rates in the area to be high, and the overall health to be low. May even have been going on long enough for insurance companies to notice.

My impression is that, bloggers screaming "cover-up" notwithstanding, the various US health-folk are in the process of checking. Wat with the general background of paranoia in the US, I imagine Texans will be buying a lot more bottled water from now on.

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