Results tagged “radiation”

Thirty-two years ago today, I noticed that things were odd at our pre-school. The teachers had drawn the blinds closed in a few rooms and at least one of the other kids had had his mom pick him up in a big wood-sided station wagon before the day was actually over. I didn't really know much more about what was going on, or why the day was strange, until years later I read much more about the accident at Three Mile Island and realized that since my pre-school and my home were just ten miles from the reactor meltdown, it's surprising that the parents of our classroom full of three year olds weren't more disturbed.

The accident's been on my mind a lot lately since the horrible earthquake and tsunami in Japan has put the Fukushima plant at risk. Beyond the obvious parallels, one thing that's stuck with me is that, aside from being a very young kid at the time, I hadn't originally known very much about what the hell actually happened at Three Mile Island, and much of that was because I didn't really know how nuclear power worked, or what the real risks were, or what had actually happened at TMI. Fortunately, even in that pre-Wikipedia era, the information was pretty easy to get hold of, because local papers back then were very interested in accurately covering the story.

When I was a kid, "TMI" was synonymous with "Three Mile Island". It's only since I've been an adult that it's ironically come to mean "Too Much Information". Because that's obviously not the case with news coverage of the Fukushima reactors here in the U.S. Fortunately, I did have access to an expert who could truly explain the context and severity of the threat at hand.

An Expert's Voice

Most of the folks I know online have seen Randall Munroe's Radiation Dose Chart. Randall's an acquaintance, and I'd been following his work since the beginning of XKCD, so I knew that he had a physics background and is a diligent researcher, so his work would be fact-driven and as accurate as possible. He talks about his sourcing and his caution in more detail on his blog, and on the whole I was very pleased with how meticulous he was.

But in my case, I had an unfair advantage: My father-in-law Stephen Browne is actually a health physicist, an expert scientist trained in measuring the amount of radiation that people are exposed to, and tracking it against the amount of exposure that's permitted. After he'd done a really insightful radio interview about his perspective on the dangers at hand, I'd sent him Randall's illustration and asked for any feedback or comments he had on it. He's kindly agreed to let me share them here, and I'll try to filter back any questions raised if clarifications are needed. His response to the XKCD Dose Chart follows. (I've added emphasis for clarity, but not changed any of the text.)

Well, the individual dose numbers are about right, but you cannot sum numbers which represent dissimilar things, such as one-time hypothetical exposure events, annual average exposures, thresholds for biological effects, and regulatory limits. Also, partial body doses (e.g., x-ray of hand, chest, arm, and mammogram) cannot be compared to whole body doses without an additional weighting factor. It would be better to just list the numbers in ascending order to show their relative magnitudes.

I think it would be more helpful for people to look at the two charts discussed below which were produced by the National Councial on Radiation Protection & Measurements (NCRP), a scientific body chartered by Congress.

• The first chart breaks down the total dose to the U.S. population by major category. The magnitude of the average dose in the U.S. is about 620 millirem¹ per year, of which 50% comes from natural background and 48% from medical exposure.

• The second chart breaks down the collective occupational dose in the U.S and shows the groups receiving the greatest collective dose are medical and aviation -- not what most people would guess.

The public also ought to know that the fatalities attributable to radiation exposure from the two most serious previous commercial nuclear power accidents are very low.

• TMI = 0 deaths or injuries
• Chernobyl = 28 short term deaths among plant and emergency response personnel from acute radiation syndrome
  and 15 excess deaths from thyroid cancer. There were many more cases of thryroid cancer but, being that it is one of the most treatable forms of cancer, few deaths. These numbers are based on the recently published report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) which looked at peer-reviewed studies of the radiation effects on populations over of a period of 20 years after the accident. You will hear claims that tens of thousands to a million deaths were caused by Chernobyl, but that is false. Those numbers are projected deaths based on cancer risk per unit dose x collective population dose, which is an invalid method because low doses carry no risk. Actual cancer death estimates can only be determined from post-accident epidemiological studies, which is why it has taken 20 years.

¹ 100 millirem = 1 millisievert (mSv)

I was really delighted at the amount of clear detail expressed there, and that a lot of facts that I think are underreported in most media sources seemed very comprehensible. There was also some great insight into how the media is often miscommunicating about the very measures of exposure:

It is not easy to make all of this stuff understandable to a layman and still get it technically correct.

One of the common problems I see in the media is the failure to distinguish between dose and dose rate. That's like mixing up miles and miles per hour. It makes a lot of what is reported confusing and hard to interpret.

Moreover, risk of harm is a function of both dose and dose rate. The same total dose spread relatively evenly over weeks, months, or years (chronic exposure) carries much lower risk of harm than the same total dose received over minutes, hours or days (acute exposure). This has to do with the body's ability to repair damage at the cellular level. So you can't really estimate risk accurately without knowing something about both dose and dose rate.

You are now starting to see a lot of reporting of radioactivity levels in food and water relative to government established concentration limits. Internal exposure is much more complex than external exposure. However, it is important to understand that accidental consumption of something that is above the limits, perhaps even many times greater than the limits, does not automatically mean the person is at great risk of harm. In general, it would take repeated or prolonged consumption at levels above the limits to have a significant risk as all limits are set very conservatively. Essentially, the risk is a function of the accumulated internal dose. The radioactivity concentration limits for food and water are just derived values, meaning you start with a dose limit and calculate backwards to find the concentration that, based on a complex set of assumptions and models, would deliver a certain internal dose to a hypothetical person in a given period of time.

Spread The Word

While I was very pleased to get this level of detail about the actual measures and dangers of radiation exposure, I have been a bit disappointed in the reality that more people don't know about these basic facts. This may be doubly true since I'm part of one of the world's preeminent organizations that's dedicated to sharing scientific knowledge.

So, I'm gonna make an unusual request: Please share this link with your social network. I've never asked people to tweet about or blog about what I write, but I am still optimistic that sharing actual facts through these networks can counteract the disinformation or misinformation that gets sensationalized in other media. And maybe we can do a bit to counteract that. And of course, if you've got links or comments with more details, please feel free to add them.

Following up on Indian Mango Alert Level: Orangish-Green and A Matter of National Security, some data points:

• The national flag of India has stripes of orange and green on a white background, The orange ("deep saffron") represents renunciation, and the green represents fertility.
• The U.S. Homeland Security Advisory System defines green on its scale as the color for a low threat level, with low risk of terrorist attack. Airports and New York City, where I live, are currently at threat level orange, which designates a high risk of terrorist attack.

Interestingly, as I was going to mention and John Dowdell pointed out, part of the ostensible reason for the reluctance to import Indian mangoes in the past was the risk of fruitfly larvae tagging along for the ride. The solution? A new irradiation process that kills the mango seed weevil. Kind of a nuclear security program for fruit.

If only that irradiation were powered by the nuclear fuel that India had gotten as part of its trade agreement with the U.S., we'd have a nice little circle of nuclear-mango life.

Here's some examples of how graphic artists are trying to save people's lives.

Prince Pickles is the manga-style cartoon character who represents Japanese Self-Defense Forces troops deployed in Iraq. Sure, he's cute, but some cartoon characters used alongside Japanese troop deployments are credited with possibly reducing violence against the troops:

[O]fficials in Tokyo say their cute offensive is working. During the mission to Iraq, the SDF decorated water trucks with a figure from a globally popular Japanese soccer cartoon, variably known as Captain Tsubasa in Japanese, Flash Kicker in the United States and Captain Majed in Arab countries.

"Everybody loved it," said Aki Tsuda of the Foreign Ministry's aid department.

Some have even suggested that Captain Majed was the reason the Japanese trucks weren't attacked during the2 1/2-year mission there, although the general area of deployment itself was relatively violence-free.

Somewhat less successful, to my untrained eye, is this attempt at making people flee in terror from sources of radiation. The International Atomic Energy Agency commissioned the work as an attempt to find a sign that would communicate with a large number of people, regardless of their cultural or linguistic background.

The new symbol is aimed at alerting anyone, anywhere to the potential dangers of being close to a large source of ionizing radiation, the result of a five-year project conducted in 11 countries around the world. The symbol was tested with different population groups - mixed ages, varying educational backgrounds, male and female - to ensure that its message of "danger - stay away" was crystal clear and understood by all.

"We can´t teach the world about radiation," said Carolyn Mac Kenzie, an IAEA radiation specialist who helped develop the symbol, "but we can warn people about dangerous sources for the price of sticker."

To me, the red triangle pretty clearly says, "You're a fan of pirates, right?"