Implying that it goes through a process that reduces half life is misleading and is misleading in the Kyodo Q&A.
Here's the EPA:
Drinking cesium-137 contaminated water, would also place the cesium-137 inside the body, where it would expose living tissue to gamma and beta radiation.
www.epa.gov/rpdweb00/radionuclides/cesium.html
and
http://www.britannica.com/facts/5/396674/cesium-137-as-discussed-in-poison-physiologyFacts about cesium-137: toxicity of whole-body radiation, as discussed in poison (physiology): Toxicities of whole-body ionizing radiation:
Radioisotopes that are absorbed and distributed evenly throughout the body also can result in whole-body irradiation. Examples are tritium and cesium-137, both of which release beta particles that can lead to bone marrow toxicities and even, in the case of cesium-137, to death. The toxicity of tritium is less severe than that of cesium-137 because the beta particles generated by tritium are...
http://us.mobile.reuters.com/article/healthNews/idUSTRE72N6LJ20110324NOTE: this was March 24th, levels are far worse now and have been detected in the US water and milk supply
Thu Mar 24, 2011 3:25pm EDT
Below are the three radioactive substances health experts are most concerned about, the detected levels in Japan, and what they mean for human health:
CESIUM-134 and CESIUM-137
Vegetables in Japan have also been tainted with up to 14,000 becquerels of cesium for every kilogram.
That exceeds the EU limit by over 11 times.
Eating a kilogram of such tainted vegetables every day for a month would accumulate radiation equivalent to a full body CT scan - or 20 millisieverts.
External exposure to large amounts of radioactive cesium can cause burns, acute radiation sickness and death. It can also increase the risk of cancer. Ingesting or inhaling cesium allows it to be distributed in soft tissues, especially muscle tissue, increasing cancer risk. It can also cause spasms, involuntary muscular contractions and infertility.
Unlike iodine, uptake of radioactive cesium cannot be prevented once the person is exposed.
This substance is of more concern than iodine-131 because it is very hardy and takes far longer to disintegrate.
Cesium-137 has a half life of 30 years, meaning it takes that long to reduce its radioactivity by half. It will take at least 240 years for this contaminant to exhaust all its radioactivity.
Cesium-134 has a half life of 2 years, which means it will take about 20 years for it to become harmless.