Need help understanding the Air Sampling Results
Regarding the Air Sampling Results, can someone who is qualified please help me understand the number in the parenthesis supplied for the general public, which is supposed to show the number of years you would need to breath the air for it to equal radiation dose on a round trip flight to DC?
For example the results for I-131 on 3/29-3/30 show (1.86E+03) I do not understand how this relates to number of years.
I apologize in advance for my ignorance and also if this question has already been asked on a previous thread, I have checked nearly all of them and did not find any information.
Also a second question concerning the I-131 in milk. If I were to freeze my dairy products for a period of 90 days before use would this give enough time for the I-131 to completely finish the decay process with no detectable levels left behind?
Thank you for taking the time to answer these questions.
Also thank you to the Professors, staff, students and all involved for your tireless dedication and the incredible service you are providing.
For the data on 3/29-30 for
For the data on 3/29-30 for I-131, the value in parentheses (1.86E+03) is the number of years you would need to breathe the air to end up with the same radiation dose (total effective dose equivalent) as a cross-country plane trip. That number -- 1,860 years -- is a very long time.
For how we arrived at that and other dose equivalences, please go to our dose calculation page.
As for I-131 in milk, the measurement we made of 0.70 Bq/L in one of our milk samples. The number in parentheses (3,800) indicates the number of liters of milk you would have to consume before you end up with the same radiation dose as a cross-country plane trip. Again, this is a lot of milk.
If you want to avoid the I-131 in milk entirely, you are right that you can wait for a period of time. The half-life of I-131 is 8 days. So for the milk we measured that has an I-131 activity of 0.70 Bq/L, after 8 days it would have an activity of 0.35 Bq/L. After 16 days it would have an activity of 0.18 Bq/L, etc. With our sensitive equipment, we cannot detect I-131 below 0.14 Bq/L, so about two weeks would be enough for us not to see anything.
Does of radiation to living
Does of radiation to living tissue is measured in sieverts. The number in parentheses is how long you would need to breathe the air contaminated at that level to equal the same number of sieverts (microsieverts) as the equivalent plane trip.
However, a growing body of evidence supports a different outcome if the same number of sieverts is applied to the whole body, vs. ingesting said particles. You would get the same dose, but in the latter case it would have a more profound effect because the radiation is localized to one place in your body.
The UC folks have suggested that they might need to alter their model based on these observations.
Reading Number of Years & Freezing Dairy-Full Radioactive Decay
These are two excellent questions. I am looking forward to the answers as well!