You statement about drinking rain water is misleading
Thanks for publishing these measurements. Your statement here is misleading:
At this level, you would need to drink 632 liters of this rain water to obtain the same radiation effects you obtain on a round-trip flight between San Francisco and Washington D.C
You have measured concentrations of I-131 up to 8 Bq/L (216pCi/L). EPA guidelines for drinking water have a Maximum Contamination Level of .11 (3pCi/L). This is also stated as 4 millirems per year.
EPA Facts About Iodine
Your measured concentrations exceed EPA guidelines by 72 times.
As others have stated the exposure on a flight is not ingesting radionuclide beta emitters.
How will the fallout affect the ocean & its living creatures?
Is there any chance the radioactive particles can sink into the deep crevices of the ocean and cause an ancient sea creature to mutate and awaken? Also, can such a mutation cause such a creature to grow to enormous size and start attacking our cities? If so, have scientists possibly figured out a way to control Godzilla enough to get him to defeat aforementioned ancient sea monster? Seriously, how will the Pacific handle the fallout?
Will you be testing tap
Will you be testing tap water as well? If so, how soon?
Two things
First of all, rain water is not drinking water. Although we are calculating the effects of drinking the rainwater, rainwater is never held to drinking water standards. In fact, I'm sure that other pollutants in rainwater (regardless of the Japan incident) fail to meet EPA standards for contaminants in rainwater.
Second of all, our comparison of exposure on a flight to ingested radioisotopes is valid. The NRC ALI (Annual Limit on Intake) takes into account the fact that the ingested radionuclides are absorbed into the body and remain for a long period of time. The calculated dose per liter rainwater is therefore the total radiation dose you would get over many years, from the ingestion of this radionuclide. So this is in fact comparable to the radiation dose received on a plane flight.
can you show your work?
Hello Brian,
Thanks again for publishing your results and answering question. Can you post exactly how you arrived at these results?
632 Liters of Rainwater contaminated with 4.26 Bq/l comes to 2692.32 Bq
For a typical cross-country flight in a commercial airplane, you are likely to receive 2 to 5 millirem (mrem) of radiation
http://www.epa.gov/radtown/cosmic.html
how is it that you are able to say 2692.32 Bq is equivalent to 5 millirems? You mention the NRC ALI. Can you show your work?
Surly you must understand that by making such and analogy you are telling people that this rain water is safe to drink. In fact it is not safe to drink under any of these guidelines:
California State Water Resources Control Board
1.85 Bq/L
EPA Drinking Water Guidlines
0.111 Bq/L
NRC (occupational Drinking water)
4.0 Bq/L
No one is implying that rain
No one is implying that rain water is safe to drink. My take is that the calculation of the amount of rain water needed to accumulate the total effective dose equivalent was provided as a conservative illustration of the magnitude of radioactive particles in the rain water.
Click here for an answer to your question.
Please remember to be courteous and respectful in your inquiries. This forum is provided as a public service after all, and we should be grateful to the scientists for the transparency of their work and the eagerness and grace with which they face the public concern and scrutiny.
duration of this event and how the calculation was performed
See this page for an explanation of how the dose was determined. First of all rainwater is not drinking water it is diluted in the aquifer, reservoirs, etc. prior to reaching the tap. These guidelines also assume you are going to drink this water every day for the rest of your life while this event isn't expected to last more than a month.
Ok, so the working
Ok, so the working assumption is that for I-131 we receive 68.49 millirems per microcurie. Using that conversion factor you arrive at 0.0078 millirem/L. Now does that conversion factor assume an adult thyroid? My understanding is that higher concentrations of radionuclides more rapidly bio-accumulate in children due to the smaller mass of their thyroids. Therefore, wouldn't the conversion factor have to be a larger value to accurately state the biological effect on children of ingesting I-131?
Without any specific
Without any specific biological knowledge, I can just say that the equivalent dose is based on the total amount (and type) of radiation energy deposited. So the concentration (radionuclides per unit mass or volume) is not as relevant as the total quantity. I am not familiar with how the NRC ALI values are derived with respect to adult or child thyroids. Children may have a somewhat higher sensitivity to dose; however, I might also postulate that a smaller thyroid would have a lesser total uptake of iodine. (At some point the thyroid is saturated from iodine, and additional iodine entering the body will flush out with a relatively short biological half-life.)
If anyone has additional quantitative information on differences between adult and youth radiation effects, that would be interesting. But it is a bit beyond the main scope of our work.
I saw this sited
I saw this sited online:
[NRC NUREG 1.109 rev. 1 Oct. '77 gives 0.0139 milliRems thryoid dose per pCi of I-131 for infants; and 0.00195 mRem for adults
I was unable to find the original document. Maybe this is software? I don't know. Am I correct that this would translate into
childred: 139 milliRems / microcurie
adults: 19.5 milliRems / microcurie
?
Assuming 139 millirems per
Assuming 139 millirems per microcurie as the conversion factor for infants and a concentration of I-131 of 8.1 Bq/L Then to reach your 5 millirem dose level the infant would only have to ingest 164.3 Liters of water.
Max Contamination Level <> radiation
I'm hope these aren't answered elsewhere,
In the formula used to estimate effects of injecting particles, how long is the particle estimated to be in the body?
How much of the "background radiation" enters the body as a particle before irradiating the body?
I want to know how measuring radiation over a period of time can be compared to ingesting a radioactive particle which lodges in your body (if that is in fact what it does). It seems the cells next to the particle would receive doses higher than could be measured using airborne measurement scales altogether.
Is it true that some radioactive particles do not leave the body? If so, what does this mean "combined biological and radiological removal"?
A particle (a radioactive
A particle (a radioactive atom, specifically) stays in the body for some time, until the body through normal processes gets rid of it. This differs for different elements, and this is measured by the biological half life. http://en.wikipedia.org/wiki/Biological_half-life
This is longer for heavy metals (~40-100 years for Pu) and shorter for lighter elements (~days for potassium).
This is best illustrated by water: you drink water every day (I hope) and it leaves your body through urination. One molecule of water might be in your body for a day or so.
Radioactive particles are only dangerous when they decay, and the longer one stays in your body, the greater the chance of it decaying inside your body and causing some damage.
Most "background radiation" is radon (inhaled into the lungs) or potassium (ingested through food), and it primarily causes damage by decaying inside the body.
This would be a good time to point out that "background" levels are quite low, and the body has a remarkable repair ability for the damage caused by a small amount of radiation.
When we measure radiation over a period of time, it's equivalent to measuring how many decays would occur inside a human body for that number of radioactive particles, and this is proportional to the damage that body would receive. Yes, the cells next to the radioactive particle receive higher dose. This has been studied in detail, and is accounted for in absorbed dose equivalent. These numbers are different for different radiation types (alpha, beta, gamma) and for different organs of the body. See dose calculation page for details.
Not sure what you're quoting for "combined biological and radiological removal". There is a removal of radioactive particles inside the body from two processes: the normal biological removal described above, and radioactive decay of the particles (most isotopes involved decay quickly to a stable atom, and are no longer dangerous).