Milk from Little Rock and drinking water from Philadelphia contained the highest levels of Iodine-131 from Japan yet detected by the Environmental Protection Agency, according to data released by EPA Saturday.

The Philadelphia sample is below the EPA's maximum contaminant level (MCL) for iodine-131, but the Little Rock sample is almost three times higher.

Nonetheless, the EPA does not consider the milk dangerous because the MCL is set for long-term exposure, and the iodine-131 from Japan's Fukushima-Daichi nuclear accident is expected to be temporary and deteriorate rapidly.

The EPA's MCL for iodine-131 is 3 picoCuries per liter.

The Little Rock milk sample contained 8.9 picoCuries per liter. It was collected on March 30.

Three drinking water samples collected in Philadelphia on April 4 contained Iodine-131, according to Saturday's data release:
  • A sample from the city's Queen Lane Treatment Plant showed 2.2 picoCuries per liter - the highest concentration in EPA's drinking water data so far.
  • Water collected at the Belmont Treatment Plant contained 1.3 picocuries, and
  • Water collected at the Baxter Treatment Plant contained 0.46 picocuries.
Philaphelphia becomes the 14th US city with radioactive fallout detected in its drinking water.

Iodine-131 has a half life of eight days: every eight days, half of its mass decays into a non-radioactive isotope of xenon.

There is much more detailed information about this weekend's data releases from EPA in the previous post: Radiation Detected In Drinking Water In 13 More US Cities."