With much confusion over just which radioactive isotopes are considered dangerous following the Fukushima explosions, Reuters has compiled a handy overview of the key actors: iodine-131, caesium-134 and caesium-137.
For the time being only the far more inert and shorter half-life elements such as Xenon have been dispersed globally, while the more dangerous isotopes have been relatively localized, and their dispersion is limited to wind direction.
Furthermore, metrics such as halflife are relatively irrelevant for now since the release of radiation continues mostly unabated thereby producing a constant source of freshly radioactive substances.
This is all the more validated by the just released NHK data indicating a surge in radioactivity as far away as 40 kms from the plant:
“Japan’s science ministry says radiation exceeding 400 times the normal level was detected in soil about 40 kilometers from the troubled Fukushima Daiichi nuclear power plant. The ministry surveyed radioactive substances in soil about 5 centimeters below the surface at roadsides on Monday. The ministry found 43,000 becquerels of radioactive iodine-131 per kilogram of soil, and 4,700 becquerels of radioactive cesium-137 per kilogram about 40 kilometers west-northwest of the plant.
Gunma University Professor Keigo Endo says radiation released by the iodine is 430 times the level normally detected in soil in Japan and that released by the cesium is 47 times the norm.”
Experts are most worried about three radioactive substances — iodine-131, caesium-134 and caesium-137 — all of which can cause various types of cancer years later.
Caesium-137 is of particular concern as it can stay in the environment and potentially cause havoc for hundreds of years. It takes 30 years for this contaminant to lose its power by half — what experts refer to as a “half life”.
At this rate, it would take at least 240 years for the contaminant to exhaust all its radioactivity.
“Caesium-137 can last for hundreds of years. If exposed, one can get spasms, involuntary muscular contractions and may lose the ability to walk. It also causes infertility. High doses will also damage a person’s DNA and cause cancer later,” said Lee Tin-lap, an associate professor at the Chinese University’s School of Biomedical Sciences in Hong Kong.