EPA: New Radiation Highs in Little Rock Milk, Philadelphia Drinking Water

[UPDATED 4/11 with comment from FDA, in italics]
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 in water, but the Little Rock sample is almost three times higher. However, the Food and Drug Administration observes a much higher standard for milk, and all milk samples collected so far are well below that level.
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 FDA's Derived Intervention Level for iodine-131 in milk is 4700 picoCuries per liter. The EPA’s MCL for iodine-131 is 3 picoCuries per liter.
"There are a few reasons that EPA's MCL for I-131 drinking water is different than FDA's DIL for I-131 in any given food," said FDA spokesman Siobhan Delancy by email. "One of them is that EPA assumes a 70 year time period for exposure, so the MCLs are basically for continual, ongoing intake. They are meant to be as low as reasonably achievable while the DILs are meant to assure that no one will reach a specific dose that would warrant protective actions as a result of an event."
Another reason for FDA's more relaxed standard is a higher tolerance for mortality.
The Little Rock milk sample contained 8.9 picoCuries per liter. It was collected on March 30. On Sunday, EPA released data showing milk in Hilo, Hawaii with 24 pCi/L of cesium-134, 19 of cesium-137, and 18 of Iodine-131.
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."