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.
But a few experts stressed there was no need for panic yet.
Levels of caesium-137 detected in spinach in Japan over the weekend stood at an average of 350 becquerels per kilogram, well below the European Union's limit of 1,000 becquerels for dairy produce and 1,250 for all other food items.
"Becquerels are like atoms," said Pradip Deb, senior lecturer in Medical Radiations at the School of Medical Sciences, Royal Melbourne Institute of Technology University.
"A liter of milk has billions and billions of atoms ... and this is just 350."
HIGHER LEVELS OF RADIOACTIVE IODINE
Milk samples in Japan, however, have been found to contain an average of 1,210 becquerels of iodine-131 per kilogram, well over the limit of 500 becquerels imposed in the EU.
Japanese spinach has also been found with an average of 10,450 becquerels of iodine-131 per kilogram, more than 5 times the EU limit.
One mitigating factor though is that iodine-131 has a half life of 8 days, which means it will take 80 days to lose all its radioactivity -- assuming there is no fresh radioactive spillage.
Source : http://www.newsdaily.com/stories/tre72l501-us-japan-contaminants/