As many of you have probably already read, trace amounts of radioactive elements from the Fukushima nuclear disaster have been detected in EPA air filters in Seattle (as well as other West coast US cities):
The units there are picocuries per meter cubed. (Note to the EPA: Could you please, pretty please with sugar on top, use SI units when describing radiation? You're scientists. As much as I love converting Curies to Bq—and who doesn't—I'd love you even more if you'd join the rest of the world.)
What does this mean? From a practical standpoint, there isn't really any health risk from this tiny of an amount of radiation. The basil you might be growing in your windowsill—or more importantly, the milk and eggs you might be eating from Washington, Oregon and California—are unlikely to absorb enough of these radioactive elements to pose a health risk to anyone, child or adult.
(I've spent a lot of time this week, reading over the data from the Chernobyl disaster and above-ground nuclear tests to be able to write a sentence like that and sleep at night. After the jump is a bit of my work...)
From Chernobyl, only exposure to radioactive Iodine, I-131, has been associated with increased cancer risk. For towns and cities where this increased risk was observed, the contamination by I-131 was higher, millions of times higher, than we're seeing here in Seattle.
As a service to you, allow me to provide you a helpful table on this point—including Tula, Russia, a town that had cases of Thyroid cancer epidemiologically linked to the Chernobyl disaster:
I-131 Bq per square meter
Now, the data we're getting from the EPA is not directly comparable to this: The EPA is giving us data on the amount in the air, these numbers are for the amounts found on the ground.
Converting from picocuries to Bq: 0.013 pCi equals 481 microBq. 481 microBq per cubed-meter is a tiny amount of radioactive Iodine compared to what Tula, Russia was exposed to—millions of times less. Hence, my being reassured at this moment.