RADIATION IN FOOD: THE FACTS ABOUT CESIUM-137

Since the Japan disaster, we have been hearing a lot about radiation exposure in the news, including about the isotope cesium-137 . Several recent posts on this blog have also mentioned it. But what is it? And, how does it affect us? I am not an expert on cesium-137, so I did some research using reliable websites, including those of the U.S. Environmental Protection Agency (EPA) and the National Institutes of Health (NIH). This is what I came up with.

Cesium 137 is a common radioactive form of the metal cesium (cesium 134 can be present in food, but is less common). It can be in a lot of other places as well. Cesium 137 is used in some industrial processes and in certain treatments for cancer. It can be found in hospital and research laboratory waste, which is usually safely disposed of. But, as we know, it is also released into the environment by nuclear reactor accidents. This happened at the Chernobyl disaster, and has also been occurring over the past month at the Fukushima power plant.

From the environment, cesium-137 can enter growing food. Leafy vegetables and grass tend to pick it up first from the air, helped by wind currents and rain. Cattle and other animals eat grass, and from there it gets into our milk and meat. Some is also absorbed by soil and water and enters root vegetables and fish. Unlike iodine-131, which can last as little as 8 days, cesium-137 has a half-life of about 30 years. Cleanup of soil or lakes or rivers is very difficult and costly. It also creates a high level of risk for the workers doing it.

The problem is that you cannot feel, smell or taste cesium in your food or water. Unless you use special equipment to check for it, you don't know if you are being exposed. If you do ingest it, this metal is apparently easily absorbed by the GI system. Some would be excreted through urine, but a portion would build up in your body, especially in the muscles. The cells lining the intestine and stomach are particularly vulnerable.

Exposure to enough cesium 137 can raise your lifetime risk of cancer fractionally, for example, from 20% to 24%. It can also cause genetic and developmental problems or result in other damage to organs. In the short term, sizeable exposure (unlikely with food or water) may give you headache, diarrhea, bleeding gums, nausea, vomiting and even fever. The size of the dose, and how regularly and how long you keep eating the contaminated food will determine how much you are affected overall.

As with almost all contaminants in food, health effects of radiation will partly depend on who you are: your age and general health, although case studies have documented mysterious exceptions to the rule. Again, as with many contaminants, if the doses are few and small, the cesium-137 will not affect your health. But if your consumption of cesium-contaminated food is "acute" or regular over a long enough period of time, especially if you are also getting radiation from other sources (such as the environment, X-rays, your occupation, international flights, or whatever), it can add to these other sources of cesium and damage your health.

Yes, there are several tests for cesium-137, that can measure levels of it in your urine, blood, bones, feces, hair or skin. But don't expect such tests to be widely available. Most medical laboratories don't do them. If diagnosed with dangerous levels of cesium-137 in your body, treatments are available.

TSF

MORE ON RADIATION IN FISH AND SHELLFISH

I blogged on March 27 about the likely risk of radiation contamination of fish and shellfish near the Fukushima power plant. That was over a week ago. It was also before we heard about the tons of radiation-contaminated water flowing into the sea near the Fukushima power plant. In fact, the latest numbers say about 7 tons of radiated water an hour is flowing into the sea from that crack in the pit at the damaged Reactor No. 2 (where ongoing efforts are now resorting to newspaper and sawdust to plug it). It was also before concerns about radiation in fish affected fresh fish sales in Tokyo, and before the media began to discuss it all over the world, including in the U.S.

And, it was before there were any reported findings of radiation in seafood near the Fukushima plant. The International Atomic Energy Agency has now reported that at the port of Choshi, in Chiba prefecture south of Fukushima, about 20% of the fish caught have been found to have elevated levels of caesium-137 (not high enough to be considered unsafe - yet).

Caesium-137? Isn't everyone talking about iodine-131? Well, yes. But most radioisotopes, including Iodine-131, have pretty short half lives (the time it takes for half the amount that initially enters the water to decay), measured in days or weeks. Testing may show elevated levels in surface seawater now (and I bet it's in lakes and rivers too) but it will get diluted, and soon just decay. In fact, the International Atomic Energy Agency said iodine-131 in seawater would “soon be of no concern.”

But other radioisotopes such as caseium-137 and stronium-90 can stick around for a long time - years, and even decades. I gather from the research on Chernobyl, that if it's in water bodies it's likely to sink down into the sediment and bioaccumulate (that is, build up) in the fish and shellfish in the area.

I wonder when we'll hear about the levels of caesium-137 found in seafood in rivers and lakes near Fukushima? I would guess, pretty soon.

By the way, I notice that my local store has stopped selling scallops imported from Japan.

TSF