I recently wrote this post about the concerns about mercury in fish, only to learn that many of you are just as worried (or more so) about radiation in fish after the April 2011 disaster with Japan's Fukushima nuclear power plant.
Frankly, the information out there is conflicting and vague, but I've done tons of reading and here's what I've learned:
First, let's look at what we know about radiation in general:
According to Andrew Maidment, an associate professor of radiology at the University of Pennsylvania, the average person is exposed to 3 mSv (millisieverts) of ‘background radiation' every year from the sun, airplanes, and even eating bananas. The lowest dose known to cause cancer over a period of one year is about 100 mSv and the average amount of radiation that will cause immediate radiation poisoning is about 400mSv. (source)
Now you and I both know that individuals are different – so the amount of radiation it may take to create negative effects is going to vary from person to person depending on their overall health and constitution.
You can see more relative radiation exposure amounts in this infographic below.
The element most commonly discussed when it comes to fall out from nuclear accidents and weapon testing is caesium. Small amounts of caesium-134, caesium-137, and iodine-131 were released into the environment during nearly all nuclear weapon tests and some nuclear accidents, and are not otherwise produced in nature.
Whereas caesium-134 has a half-life of 2 years, caesium-137 has a half-life of 30 years and iodine-131 is 8 days, meaning it takes that long for half of the radioactive atoms in each substance to disintegrate. As such, caesium-137 is the radioactive isotope that is the biggest health concern in the current aftermath of Fukushima because it is the longest lasting threat.
Is radiation in fish a concern?
To put this into perspective when it comes to fish, let's look at the worst case scenario. According to this article from Japan Times, a fish caught directly in the Fukushima No. 1 nuclear plant’s small harbor contained 510,000 becquerels (bq) of radioactive caesium per kilogram – 5,100 times above the state-set safety limit. If someone were to eat to eat 2.2 pounds of a fish with this level of contamination, they would be exposed to about 7.7 mSv of internal radiation – the same amount of radiation as a chest x-ray.
That's pretty gnarly, and I'm definitely not interested in eating a chest x-ray worth of radiation for dinner. But, the fish we eat here in the U.S. does not come from the waters around the nuclear disaster site in Japan.
So then, you many have also heard that tuna was caught off the shores of San Diego, CA, that had traces of caesium that indicated that the fish had come from the waters around Fukushima. However, you'd need to eat 2.5 to 4 tons of that tuna in a year to get a dose of cesium-137 that exceeds health limits. (source)
Personally, that's a relief to me. I'd have to eat 6.8 pounds of contaminated fish per DAY for my consumption to be toxic.
Here's my take home about radiation in fish
Just like the rest of your food – know your source.
Buy wild caught fish that are not Japanese bottom-feeders (which you're not likely to find anyway).
IF you're in Japan, find out where the fish is from. In my opinion, the health benefits of seafood outweigh the risk of radiation poisoning.
What about radiation in the rest of our food supply?
There are tons of articles online about radioactive isotopes contaminating everything from seaweed to raw milk. Is this really something to worry about?
This report from UC Berkeley logs hundreds of records of testing for radioactive isotopes in U.S. air, water, plants, soil, and milk. Nearly all of their reports come back with nearly undetectable levels.
My raw milk producer here in Southern California – Organic Pastures – also had their milk tested and found that there were no detectable amounts of radiation. (source)
Personally, I find the issue around seaweed to be the most confusing as the U.S. imports plenty of seaweed from off the coast of Japan. U.S. companies go to great lengths to claim that their products are tested, though in combing the internet, I didn't find particularly recent reports.
This article claims they personally tested seaweed at high levels of radiation – however it does not actually provide measurements of radioactive isotopes present and they give percentages over ‘background'.
If radioactive isotopes are present in seaweed, how much of this extremely non-dense sea veggie would need to be consumed to create any damage?
The answer is unclear. For me, the risks of seaweed consumption are not compelling enough to not eat seaweed. This is the brand that I buy that stands by their testing.
Are you avoiding fish or seaweed because of the risk of radiation?