Radiation from Japan has been detected in drinking water in 13 more American cities, and cesium-137 has been found in American milk—in Montpelier, Vermont—for the first time since the Japan nuclear disaster began, according to data released by the Environmental Protection Agency late Friday.

Milk samples from Phoenix and Los Angeles contained iodine-131 at levels roughly equal to the maximum contaminant level permitted by EPA, the data shows. The Phoenix sample contained 3.2 picoCuries per liter of iodine-131. The Los Angeles sample contained 2.9. The EPA maximum contaminant level is 3.0, but this is a conservative standard designed to minimize exposure over a lifetime, so EPA does not consider these levels to pose a health threat.

The cesium-137 found in milk in Vermont is the first cesium detected in milk since the Fukushima-Daichi nuclear accident occurred last month. The sample contained 1.9 picoCuries per liter of cesium-137, which falls under the same 3.0 standard.

Radioactive isotopes accumulate in milk after they spread through the atmosphere, fall to earth in rain or dust, and settle on vegetation, where they are ingested by grazing cattle. Iodine-131 is known to accumulate in the thyroid gland, where it can cause cancer and other thyroid diseases. Cesium-137 accumulates in the body’s soft tissues, where it increases risk of cancer, according to EPA.

Airborne contamination continues to cross the western states, the new data shows, and Boise has seen the highest concentrations of radioactive isotopes in rain so far.

A rainwater sample collected in Boise on March 27 contained 390 picocures per liter of iodine-131, plus 41 of cesium-134 and 36 of cesium-137. EPA released this result for the first time yesterday. Typically several days pass between sample collection and data release because of the time required to collect, transport and analyze the samples.

In most of the data released Friday the levels of contaminants detected are far below the standards observed by EPA and other U.S. agencies.

But the EPA drinking-water data includes one outlier—an unusually, but not dangerously, high reading in a drinking water sample from Chatanooga, Tennessee.

The sample was collected at the Tennessee Valley Authority’s Sequoyah nuclear plant. A Tennessee official told the Chatanooga Times last week that radiation from Japan had been detected at Sequoyah but is “1,000 to 10,000 times below any levels of concern.” The 1.6 picocures per liter reported by the EPA on Friday is slightly more than half the maximum contaminant level permitted in drinking water, but more uniquely, it is many times higher than all the other drinking water samples collected in the U.S.

[UPDATE: EPA released new data Saturday revealing higher levels than reported here in Little Rock milk and Philadelphia drinking water]

The EPA released this new data through a new interactive open-data system it quietly launched on the EPA website Wednesday. The new interface is to be regularly updated, replacing EPA’s periodic news releases and pdf data charts. Here are more details of the data released Friday:

Drinking Water

Radioactive Iodine-131 was found in drinking water samples from 13 cities. Those cities are listed below, with the amount of Iodine-131 in picocuries per liter. The EPA’s maximum contaminant level for Iodine-131 in drinking water is 3 picocuries per liter.

• Oak Ridge, TN collected 3/28: 0.63
• Oak Ridge, TN collected at three sites 3/29: 0.28, 0.20, 0.18
• Chatanooga, TN collected 3/28: 1.6
• Helena, MT collected 3/28: 0.18
• Columbia, PA collected 3/29: 0.20
• Cincinatti, OH collected 3/28: 0.13
• Pittsburgh, PA collected 3/28: 0.36
• East Liverpool, OH collected 3/30: 0.42
• Painesville, OH collected 3/29: 0.43
• Denver, CO collected 3/30: 0.17
• Detroit, MI collected 3/31: 0.28
• Trenton, NJ collected 3/31: 0.38
• Waretown, NJ collected 3/31: 0.38
• Muscle Shoals, AL collected 3/31: 0.16

Precipitation

In the data released Friday, iodine-131 was found in rainwater samples from the following locations:

• Salt Lake City, UT collected 3/17: 8.1
• Boston, MA collected 3/22: 92
• Montgomery, Alabama collected 3/30: 3.7
• Boise, ID collected 3/27: 390

As reported above, the Boise sample also contained 42 pC/m3 of Cesium-134, and 36 of Cesium-137.

Air

In the most recent data, iodine-131 was found in air filters in the following locations. In the case of air samples, the radiation is measured in picoCuries per cubic meter.

• Montgomery, AL collected 3/31: 0.055
• Nome AK collected 3/30: 0.17
• Nome AK collected 3/29: 0.36
• Nome AK collected 3/27: 0.36
• Nome AK collected 3/26: 0.46
• Nome AK collected 3/25: 0.26
• Juneau AKcollected 3/26: 0.43
• Juneau AK collected 3/27: 0.38
• Juneau AK collected 3/30: 0.28
• Dutch Harbor AK collected 3/30: 0.14
• Dutch Harbor AK collected 3/29: 0.11
• Dutch Harbor AK colleccted 3/26: 0.21
• Boise, ID collected 3/27: 0.22
• Boise, ID collected 3/29: 0.27
• Boise, ID collected 3/28: 0.32
• Las Vegas NV collected 3/28: 0.30
• Las Vegas, NV collected 3/30:: 0.088
• Las Vegas, NV collected 3/29: 0.044

No other types of isotopes were found in the most recent data from air samples, even though EPA is also on the lookout for barium-140, cobalt-60, cesium-134, cesium-136, cesium-137, iodine-132, iodine-133, tellurium-129, and tellurium-132.

In older samples, isotopes of cesium and tellurium were found in Boise; Las Vegas; Nome and Dutch Harbor; Honolulu, Kauai and Oahu, Hawaii; Anaheim, Riverside, San Francisco, and San Bernardino, California; Jacksonville and Orlando, Florida; Salt Lake City, Utah; Guam, and Saipan on the Marina Islands.

Some of these locations had not been previously reported in EPA news releases.

The EPA has said it will continue to monitor radiation levels in air, precipitation, drinking water, and milk even if the budget impasse shuts down the government next week.

There is more discussion of maximum contaminant levels and health concerns in the related links below and their associated comments: