I need physicists in here to help explain exposure to radionuclides.

[Paradoxical]

We are seeing reports of I-131 levels in rain water exceeding federal limits by as much as 181 times.

We need to understand the difference between short term and long term exposure. And we need to know the definitions for both short term and long term exposure.

I have attempted to find such definitions through the EPA. But they don't seem to define what constitutes long-term exposure.

Iodine 131 has a half life of 8 days. But it can persist in the thyroid for up to 100 days.

Does a single dose of I 131 constitute a non-negligible threat for a persons health in the future?

They appear to be measuring levels in rain-water around 550 picocuries per liter.

[FBaggins]

1. "long term" exposure is generally a year or more.

When the EPA sets safety levels, they're assuming that you remain exposed to the source all year round. If they say a given level is safe for srinking water, they mean it can stay at that level essentially permanently without appreciable risk.

Does a single dose of I 131 constitute a non-negligible threat for a persons health in the future?

Not at anything close to the level you cite. A picocurie (one trillionth of a curie) is about 2.2 disintegrations per minute... or bit more than 1/30th of a Bq. So 550 of them would be 20 Bq.

That's MUCH higher than I would expect it to be (and it's also much higher than the other readings that have been reported), but it wouldn't do you any harm. I wouldn't want to drink it all year long, but even if the reported level was accurate, it wouldn't BE there all year long.

[Paradoxical]

3. Okay but what if exposure persists for several weeks or months?

Assuming the reactor vessels are not contained and the fission process continues, 1 131 will continue to be produced.

[FBaggins]

4. Well... it won't... but let's assume that.

Assuming the reactor vessels are not contained and the fission process continues, 1 131 will continue to be produced

There isn't an ongoing fission process to "continue"... nor are there the frequent steam releases that create the "plume" that can cross the Pacific.

But let's assume that there was.

Let's further assume that all of the REST of the radiation measurements along the West Coast are just wrong and this is the one and only correct one.

Now... having presumed all of this - there STILL isn't a problem. Because people don't drink rain water all year long. The rain water slowly enters the water supply and is incredibly diluted by the existing aquifer.

[Generic Other]

2. kick

important questions