Editor's note: Two weeks ago, in an editorial about media sensationalism in general and fears of nuclear fallout from Japan's devastated Fukushima Daiichi power plant in particular, we quoted Humboldt State University Professor Richard Stepp, an expert in airborne pollutant dispersal. Stepp attempted to alleviate public anxiety with a dose of stone-cold science ("The FUD Factor," March 17). His comments sparked debate amongst our readers, who chimed in with their own learned observations on gamma rays, microsieverts and screaming atoms. The latter phenomenon (wow!) was brought to our attention by Redway resident John Hardin (see "Mailbox"). We were so tickled by all this lab talk -- and so relieved to be party to a meaty conversation on a serious subject -- that we made two moves: We elected to print Mr. Hardin's letter in full despite the fact that it exceeds our fascistic word limit, and we invited Professor Stepp back to our pages so he could drop some more knowledge:
My specialty is atmospheric dilution, so let's talk about that first. The Fukushima Daiichi nuclear power plant is approximately 200 kilometers (124 miles) north of Tokyo. If winds were to carry the pollutants across that distance, I calculate that they would be diluted by a factor of about 200,000. In other words, a person standing just outside the Fukushima Daiichi reactor buildings would experience 200,000 times more radiation than a person standing outdoors in Tokyo.
Here's an example: On Monday, March 14 at 7 p.m., immediately after one of the hydrogen explosions, the dose rate immediately outside one of the damaged reactors spiked from 73 microsieverts per hour to 11,900 microsieverts per hour, according to Yahoo News. Assuming that the rate remained steady for the 12 or so hours that it would take the wind to carry the pollution to Tokyo, a person standing outdoors in the Japanese capital would have experienced a dose rate of about 0.06 microsieverts per hour (11,900 divided by 200,000). That's one fifth of the average background radiation that's normally present at sea level.
The North Coast is about 39 times farther from the Fukushima Daiichi reactors than Tokyo, so our dose rate would be that much more diluted. That means it would be less than half a percent of the normal background radiation. By comparison, you would roughly double your background radiation danger by driving to Willow Creek on a sunny day.
In the two weeks following the initial explosions, a half dozen or so experts on the health effects of exposure have been interviewed or quoted by Yahoo News. Every one of them said that the danger to West Coast residents would be minimal. Roughly the same number of nuclear engineers were also interviewed or quoted, and they, too, stressed that while this situation might last for months, it is not comparable to Chernobyl.
Now, to Mr. Hardin's well-written letter: Most everything he says I believe is so (though I am not a specialist in radioactivity or its effects on humans). However I do disagree with him on two important points:
1) He says that "the comparison of radioactivity from a nuclear power plant to a medical X-ray is highly misleading." However, the units called "sieverts" claim to do precisely that. (Editor's note: According to the Encyclopedia Britannica, each form of ionizing radiation -- e.g., X-rays, gamma rays, neutrons -- has a slightly different effect on living tissue.) If Mr. Hardin is correct then those who use sieverts in this way are wrong. This is not my area of expertise, so I leave this debate to others -- but note that none of the quoted radioactive health physicists mentioned above appear to agree with him. I can only note that the quoted experts would have to be wrong by a factor of about a thousand to change the conclusion that West Coast health danger is minimal.
2) Regarding his comment about me as an "amateur media commentator" I say the following: I am a trained scientist -- I think with numbers. In health matters, the dose a person gets is paramount, though you wouldn't know it from reading many of the recent headlines on the matter in the national media. If the likely doses mentioned in the body of a news story don't support the screaming scary headline, then I can and do object.
I don't for one moment dismiss the dangers of nuclear power, and in this case the people living in the vicinity of these power plants will have a valid worry for a very long time. If the Humboldt Bay nuclear reactor had had an accident like that prior to its shutdown in 1976, we would have been in the same boat.
That being said, the risks associated with nuclear power should be put in the context of the dangers associated with other forms of power generation, all of which should make us reconsider our apparent unwillingness to make meaningful reductions in power usage.
One more comment regarding Mr. Hardin's letter: He criticizes "a dismissive attitude based on misleading reassurances." I would argue that nothing better fosters a dismissive attitude than crying wolf. We have a chance here to hold a substantive debate on how to value the various costs and dangers of different energy technologies. We should capitalize on that opportunity.
Richard Stepp received his PhD in meteorology, with an emphasis in air pollution issues, in 1972 from Penn State University. He has been a professor of physical science at Humboldt State University since 1973.