Is the I-131 content in water already over CDC standard

Submitted by Anonymous on Wed, 2011-03-23 22:53

Dear Sir,

Thanks for testing the rain water. According to your data, there is 4-8 Bq/liter I-131 in the water. CDC standard is 4 Bq per liter according to the following website:
http://www.atsdr.cdc.gov/csem/iodine/standards_regulations.html

Does it mean the rain water is already over CDC standard?

Thanks.

‹ When will you get a chance to measure tap water? Radiological Monitoring in New Mexico ›

you are citing occupational limits

Submitted by Raj Dye (not verified) on Thu, 2011-03-24 08:02.

BTW the link that you posted:
http://www.atsdr.cdc.gov/csem/iodine/standards_regulations.html

This is not a CDC standard, but an EPA Occupational standard. The drinking water standard is much more strict; 3 pCi/L.

http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/iodine.pdf

Presumably the occupational standards are more relaxed due to the assumption that all exposure on-the-job will be to adults. Where general drinking water standards need to apply to children, the most vulnerable to ingesting radionuclides.

--

Raj Dye

measured concentrations exceed EPA drinking water standards

Submitted by Raj Dye (not verified) on Thu, 2011-03-24 07:49.

Hello,

EPA guidelines for drinking water are 4 millirem per year, which is 3 picocuries per liter (pCi/l) for I-131.

EPA facts about Iodine-131

This amounts to a limit of 97Bq per year. At a concentration of 8 Bq/L you would exceed the EPA yearly Maximum Contamination Limit after drinking 13 liters of water.

--
Raj Dye

Raj, I think you may be a

Submitted by dchivers on Thu, 2011-03-24 17:45.

Raj, I think you may be a bit off here. The dose conversion factor for I-131 is close to 2e-8 Sv/Bq which takes into account biological half life, effect on thyroid, etc... 4mrem is 0.04 mSv or 4e-5 Sv .. so this comes out to 2000 Bq consumed. This would result in 250 L of water consumed to reach the 4 mrem limit per year. Now, since the activity will decay away in 2 months (conservative) that would mean you would have to drink an average of 8.3 L per day. A better estimate for dose is based on 2L per day for the 60 days (again very conservative) which results in something closer to 1 mrem for the avid rain water drinker.

uncertainty the Dose Conversion Factor for I-131

Submitted by Raj (not verified) on Fri, 2011-03-25 04:08.

Ok, yeah I didn't arrive at that using a dose conversion factor directly. I just took the limit of 3 pC/L and multiplied it by (2.4L) * (365 days). I figured that the EPA would use this recommend daily intake of water 2.4 Liters per day for 365 days. That results in 2628 pC or 97.236 Bq. Perhaps their statement of 3 pC/L is not the most precise and leads to errors when working backward this way.

But you can see here they state the 3 pC/L leads to exposure of 4 millirems per year

http://www.epa.gov/superfund/health/contaminants/radiation/pdfs/iodine.pdf

I wonder why you estimate the dose conversion factor here? Elsewhere on the website you use a dose conversion factor of 68.49 millirem / microcurie

The figure you give is 2e-8 Sv/Bq this converts to 77.7 millirems/microcurie Correct ?

In either case, The dose conversion factor you are using for I-131 far below these publish values:

Authority Sv/Bq
National Cancer Institute
3.50E-08
DOE (1988)
4.90E-08
EPA 1988)
4.76E-08
Killough, G.G
4.50E-08
you stated
2.00E-08

These values are all cited here:
http://web.engr.oregonstate.edu/~hambydm/papers/benke.pdf

You keep saying you are making these "conserve" estimates, but it doesn't read that way when you use this conversion factor.

--

Raj

We have not tested tap

Submitted by dchivers on Wed, 2011-03-23 23:03.

We have not tested tap (drinking) water yet. We expect the dilution to be reduce levels to well below this standard. It is also important to note that these limits are based on long-term exposure (many years) while this exposure will be very short lived (weeks). Testing the rain water is the best way to test the air because the rain concentrates all particulates into the drops. If you live near a city, just look at the clarity of the air after a rain.

Does reverse osmosis remove radioactive particles

Submitted by Anonymous (not verified) on Thu, 2011-03-24 20:45.

Can anyone throw some light on whether reverse osmosis removes radioactive particles - specifically, radioactive iodine and cesium isotopes in the current context? Given that rain water seems to already contain iodine about twice the "occupational" standard, it's very concerning!

Also, I can buy dilution of these radioactive particles in drinking water (maybe!), but what about vegetables? Can radioactive iodine from rain water collect on vegetables - say greens?

In general, iodine is best

Submitted by Anonymous (not verified) on Thu, 2011-03-24 21:10.

In general, iodine is best removed with carbon-based filters.

Thanks, any chance of

Submitted by Anonymous (not verified) on Thu, 2011-03-24 22:10.

Thanks, any chance of vegetable contamination due to contaminated rain water?

I'd like to know this too.

Submitted by physicist (not verified) on Fri, 2011-03-25 09:30.

I'd like to know this too. Just to clarify, I believe the rainwater is twice the occupational standard for drinking water, right? I'd imagine it to be much diluted on vegetables, i.e. you'd probably only be exposed to the iodine contained in a few grams of water. One related question I had is whether one can rinse off the radioactive isotopes from the leaves surface while they're still fresh. Of course you'd likely be using tap water for this purpose but that should still be somewhat more diluted than rain water.

Can somebody also comment about carbon-based filters and their hypothetical ability to remove iodine and cesium?