More Baseless Nuclear Panic

Thanks to the Fukushima accident, my coworkers and I have found ourselves fielding questions from friends and family because the media has been too busy sensationalizing and ax-grinding to do some basic research. I've tried to summarize the relevant information on this page. Unfortunately, there seems to be more panic among Americans than among the much more stalwart Japanese.

The latest unfounded fears I've come across are coming out of Boise, Idaho. Due to the Fukushima accident, elevated levels of the radioactive isotope iodine-131 were found in Boise's rainfall and drinking water. Of course, this has some people panicking. "Anonymous Coward" posted this on one forum:

We are going to get a very concentrated dose of radioactive materials tomorrow in Boise, Idaho PLUS a 90% chance of rain. Cesium 137 was detected here by air filter and rainwater. The next three days if not longer are going to be bad but it looks like only tomorrow will be raining.

Should I keep my child home from school tomorrow? Am I overreacting? Wwyd? P.S. Yesterday I felt fine, today I have feelings in my throat and a weird headache and it's raining.

Others in the forum advised the poster to keep her child out of the rain due to "high levels of iodine 131", to treat her drinking water with various "detoxification" substances, or to allow her child out in the rain to build up a tolerance because "she has many years of exposure to come." How can we have nearly all of mankind's knowledge at our fingertips thanks to the Internet and yet keep finding absurd advice like this?

It doesn't take a whole lot of research to show that Anonymous Coward's throat problems and "weird headache" are psychosomatic and not the result of radiation sickness. First of all, let's review the actual report that has some people scared. Here's the EPA's statement on precipitation from April 4, 2011:

[P]recipitation data collected in several states show elevated levels of radiation in recent precipitation events. In all cases these are levels above the normal background levels historically reported in these areas. While short-term elevations such as these do not raise public health concerns – and the levels seen in rainwater are expected to be relatively short in duration – the U.S. EPA has taken steps to increase the level of monitoring of precipitation, drinking water, and other potential exposure routes to continue to verify that. (emphasis mine)

Despite the EPA's statement that there is no public health concern, many people seem to have focused on the report's table stating that 242 pCi/L was measured in the local precipitation on March 22 (the level of cesium-137 was about 20 times lower). My coworkers and I have had a good laugh that this number has caused an uproar among some people. The pCi (pronounced "picocurie", meaning 1/1,000,000,000,000 of a curie) is an extremely small quantity of radioactivity, especially when diluted in a liter (L) of water. When we talk about contaminated water at work, we use units of µCi/mL (1/1,000,000 of a curie in 1 milliliter of water) because a pCi/L is such a small amount (1 µCi/mL is a billion times more than 1 pCi/L).

Not understanding what a small amount of radioactivity 242 pCi/L is, someone took that number, divided it by the EPA drinking water limit of 3 pCi/L for iodine-131, and then declared that "Boise rainwater has highest levels of radioactive material… 80 times amount of I-131 allowed in drinking water." Once again, someone has either failed to do their research or is deliberately trying to scare people.

Drinking Water versus Precipitation
Notice that the above calculation confuses precipitation with drinking water. The rain that has fallen since the Fukushima incident makes up only a small percentage of Boise's drinking water. So how much radioactive iodine has actually been found in the drinking water? From the EPA's April 4, 2011 statement on drinking water:

Drinking water samples from two locations, Boise, Idaho and Richland, Washington, showed trace amounts of Iodine-131 – about 0.2 picocuries per liter in each case. Even an infant would have to drink almost 7,000 liters of this water to receive a radiation dose equivalent to a day’s worth of the natural background radiation exposure we experience continuously from natural sources of radioactivity in our environment. (emphasis mine)

Even after the "very concentrated dose" of radioactivity in the rainwater on March 22, the drinking water in Boise contained a paltry 0.20 pCi/L on March 28. This isn't 80 times greater than the allowed EPA limit, it's 15 times less than the limit. And since iodine-131 has a half-life of about 8 days, the quantity of radioactive iodine will significantly decline over the coming weeks and months.

Conservatism of the EPA Limit
It's unfortunate that the unit of measurement used throughout the Fukushima crisis has been 'X times (normal levels, regulatory limits, etc.)'. I understand that this is an attempt to give people a sense of scale, but since most don't actually know the levels at which radiation or radioactivity become dangerous (and the media doesn't seem to be in a hurry to tell them) you end up with people who are in possession of the facts but don't know what they mean. For example, ten times the normal radiation levels sounds scary until you realize that normal radiation levels are nearly 100,000 times lower than the levels at which the signs of acute radiation sickness appear (the average American receives about 1 millirem (0.001 rem) per day from normal background radiation, while radiation sickness generally occurs after receiving about 100 rem).

The EPA's limit for iodine-131 in the drinking water is an average annual level of 3 pCi/L "so the public radiation dose will not exceed 4 millirem". The limit was chosen as one that was so low that a person could ingest it every day from infancy to old age with no statistically detectable ill effects. Like so many other EPA limits, this number is relatively arbitrary. Although levels vary, the Department of Energy has estimated that the average American receives 360 millirem/year due to background radiation (some have estimated even higher levels due to the increased use of certain medical technologies). The 4 millirem that one could get from drinking water containing the EPA limit of iodine-131 would therefore account for a mere 1% of the radiation a person would normally receive. Even if the scary '80 times the EPA limits for drinking water' were accurate, and if it were assumed (unrealistically) that levels in the water would remain elevated for a whole year, people in Boise would only receive an extra 320 millirem per year (4 millirem times 80) from the contaminated water. Compare that to the 5,000 millirem per year that nuclear workers are allowed to receive per Federal law. Also per Federal law, a pregnant nuclear worker is allowed to receive 500 millirem for the duration of the pregnancy. These Federal limits are what workers may receive beyond normal background exposure. In short, even in an unrealistic worse case scenario, the people of Boise would receive lower radiation doses than have been shown to be safe for unborn children (320 millirem versus 500 millirem).

Precedence
A brief review of the data shows that the 242 pCi/L of iodine-131 found in Boise's rainwater are less than the levels found after the Chernobyl accident in 1986. On May 8, 1986, 460 pCi/L were found in the rainwater in Portland, Oregon. On May 10, 530 pCi/L were found in Las Vegas, Nevada and 270 pCi/L were found in Olympia, Washington. In Ottawa, Canada even higher levels were found; samples taken on May 7, 1986 found 1,647 pCi/L in the rainwater. These levels were all higher than those found in the United States following the Fukushima accident, yet there were no cases of radiation sickness nor was there a noticeable increase in cancer rates in North America. According to the EPA, such levels are low enough that they "pose no threat to human health or the environment."

Even the contamination spread by the Chernobyl disaster is dwarfed by the amount of radioactive fallout produced by years of nuclear testing between the late 1940s and the early 1960s. The United States alone performed 331 nuclear weapons tests above ground (and even more underground). Many of these tests were conducted in Nevada, about 100 miles from Las Vegas, while the largest tests were performed in the Pacific. The Soviet Union conducted 715 tests, often without regard for the health of those living nearby. One Soviet test involved the largest nuclear weapon ever detonated (50 megatons versus the 15 megatons of America's Castle Bravo test). Each of these above ground tests blasted huge quantities of radioactive materials into the stratosphere. Since humanity somehow managed to survive almost twenty years of fallout resulting from the nuclear arms race, I think it's safe to say that Anonymous Coward of Boise, Idaho and her child will tolerate the radioactivity spread by the Fukushima accident just fine (I'm not sure how well she'll handle the psychosomatic effects, though).

Castle Romeo vs. Fukushima: which do you think caused more fallout?

In conclusion, as I've said before (here and here), the levels of contamination reaching the United States are very low and present a negligible risk to human health. Unfortunately, members of the American public who have little to no knowledge of nuclear power (e.g., Anonymous Coward) have latched onto numbers that seem large and have started to panic. This hasn't been helped by those who have taken a single day's measurement of radioactivity in rainfall (which yielded a number with units that they don't understand) and have compared it to a regulatory limit for drinking water (without understanding the origin of the limit or how that limit compares to actual biological effects). Rather than try to confirm or correct their perceptions using the power of the Internet, these people gather on various forums to scare each other instead. I find myself wondering how many of these people drive without wearing a seatbelt.