Apr. 27 — A radioactive isotope of strontium has been detected in American milk for the first time since Japan’s nuclear disaster—in a sample from Hilo, Hawaii—the Environmental Protection Agency revealed yesterday.
“We have completed our first strontium milk sample analysis and found trace amounts of strontium-89 in a milk sample from Hilo, Hawaii. The level was approximately 27,000 times below the Derived Intervention Level set by the U.S. Food and Drug Administration,” EPA said in a statement emailed to me yesterday afternoon. EPA posted the test result at epa.gov in a pdf.
EPA found 1.4 picoCuries per liter of strontium-89 in a milk sample collected in Hilo on April 4.
Although the EPA tests milk, the FDA regulates it, and the FDA’s Derived Intervention Level—the standard observed for food—is 4,400 pCi/L for strontium-90. I’m working to confirm whether FDA has a separate DIL for Sr-89.
The EPA’s Maximum Contamination Level for Sr-89 in drinking water is 20 pCi/L. (For more on the difference between EPA and FDA standards, see “Why Does FDA Tolerate More Radiation Than EPA?“)
The two man-made isotopes of strontium—Sr-89 and Sr-90—are among the most dangerous products of nuclear fission to human and animal health. Both are “bone-seekers,” chemically similar to calcium, that collect in bone and marrow, where they are known to cause cancer. They are particularly dangerous to the growing bones of fetuses and children.
The half-life of Sr-89 is 50.5 days, and Sr-89 is sometimes used as a cancer pain treatment under the commercial name Metastron, because it collects in and destroys the fast-growing cells of bone cancer. EPA considers Sr-90, meanwhile, “the most important radioactive isotope in the environment” because of its health impacts and a longer half-life of 29 years.
EPA has found no strontium-90 in its testing, according to the statement, and it has found neither of the strontium fission products in drinking water.
Where’s the strontium? has been a question pressed by nuclear watchdogs—including one of the participants in this forum, liberationangel—since the Fukushima Dai-Ichi nuclear disaster. And not only where, but why aren’t the hazardous man-made isotopes of strontium included in the EPA’s open data system?
EPA does not list strontium in that system, I have learned, because it does not routinely test for strontium, even during its increased testing since the Fukushima disaster.
Tests for strontium are triggered by the presence of cesium isotopes, which have been found in milk from Hilo, Montepelier VT, and Oakland and in precipitation from Boise, Richmond CA, Salt Lake City and a few other cities.
The Strontium-89 was found in April 4 Hilo samples previously found to contain cesium-134 and cesium-137, and the test results were released only yesterday because they take longer to analyze, according to EPA’s statement:
In response to the Japanese nuclear power plant release, if we identify radioactive cesium… those samples will be analyzed for strontium. Testing for strontium is a complex process that takes time.”
More cesium was found in a Hilo milk sample on April 13. All of EPA’s initial milk testing is available here.
Some bloggers and activists have accused EPA of finding and then concealing plutonium and strontium in U.S. test results. The accusations seem to stem from searches of EPA’s more complicated Envirofacts database, which EPA made available to the public only recently in response to the Fukushima disaster. The database had previously been restricted to scientists.
The quantities of strontium and plutonium listed in that database are so minute—for example, 0.0008 picoCuries per cubic meter, and, in another case, a negative number: -0.00013 pCi/m3—and they are so dwarfed by the margin of error, that EPA categorizes them as “non-detectable,” according to the EPA statement sent to me yesterday:
It is important to note that Envirofacts contains all data points, including negative numbers and numbers we consider to be non-detects, because having all the results is important for technical experts to gain a complete understanding of the situation. A data point is considered a non-detect when it is less than or equal to twice the combined standard uncertainty (which is listed on the Envirofacts tables).
Thus, numbers that appear in EnviroFacts as minute or negative quantities of strontium and plutonium may appear as “non-detectable” in public data releases. EPA reported at the end of its business day yesterday there have been no detectable strontium or plutonium readings other than the Hilo result.
Apr. 27 2011 – 8:45 am