Fight or flight is one of our most primal reflexes – faced with a potential danger we tend to turn one way to confront it or the other way to flee to safety. Fighting was not an option for the public in the aftermath of the accidents in Fukushima and Chernobyl – just as it is unlikely that the population of, say, New York City will head to the north if the Indian Point Nuclear Power Plant—about 35 miles north of Manhattan—suffers a problem (not to mention responding to an attack with a radiological weapon). The first impulse of the population is to try to get out of harm’s way, and the first impulse of the government is to try to move its citizens out of harm’s way. Let’s face it – if a cloud of radioactivity is heading towards you what can be more natural than to try to move yourself and your family out of the way? People tend to self-evacuate – who can forget the pictures of people streaming over the Brooklyn Bridge after the September 11 attacks? – and governments tend to want to evacuate those left behind.
The problem is that evacuation is not always the answer and evacuation is not a risk-free event. There are times when trying to move yourself – or your citizens – out of harm’s way is actually riskier than leaving them in place.
Consider – virtually all of New York City’s people live within 50 miles of the Indian Point Nuclear Power Plant and the northern-most part of Bronx lies about 25 miles away. Evacuating 10 million people to “safety” would mean driving them into New Jersey, Connecticut, or into eastern Long Island. So say we put 10 million people on the road and try to move them 50 miles – that’s about 500 million person-miles of driving. The risk from driving varies according to where you live but they are not trivial – if we assume a low value of 2 deaths per 100 million passenger-miles then 10 people would be expected to die evacuating New York City – more if even a single bus overturns, as has happened several times in the last year alone. Whether the actual number would be higher (due to people driving poorly and panicking) or lower (due to slow speeds on clogged highways) we can’t guess. But the bottom line is that there is a very real risk from evacuation and it behooves us to try to determine whether the risk from evacuation is higher or lower than the risk from a radioactive plume.
Indian Point published multiple studies of radiation dose to the population from a variety of accident scenarios – reviewing these studies suggests that radiation dose to people who remain in New York City would be too low to cause any demonstrable health problems to the population. In fact, the radiation dose to the average New Yorker would be comparable to a few x-rays – not nothing, but well within the natural variability we are exposed to as we travel from place to place on Earth. If we assume that traffic statistics are applicable in an emergency evacuation then it is likely that a forced evacuation would save no lives and might actually increase the risks to the population of the city. In other words, our instincts might serve us poorly.
Interestingly, immediate evacuation might not make much sense in the case of a nuclear or radiological attack either. Radiation dose in the fallout plume from a terrorist nuclear attack might be rapidly fatal while moving indoors can cut this dose to levels that are easily survivable. So, picture yourself standing in Maryland and seeing a nuclear detonation over Washington, DC and realizing that the wind is blowing your way. Fleeing is a natural reflex –for you and for about a million of your fellow citizens. Of course you need to get out of the plume – if you simply try to drive directly away from the source of the explosion you’ll be driving down the axis of the plume and receiving a huge radiation dose; driving perpendicular to the plume axis is a better bet, but even here you have to be assured of clearing the area before the plume touches down. On the other hand, if you go indoors – preferably into a basement or into the core of a large building – you are likely to receive a fairly low dose of radiation that will almost certainly be survivable. In fact, according to some U.S. government estimates, going indoors immediately (rather than immediate evacuation) can save up to a half million lives in some cities. The moral of the story is that evacuation can be deadly and hunkering down can save your life.
We saw this in Japan, by the way. I was in the Fukushima area a month or so after the accident and my radiation measurements (which were consistent with those reported by the IAEA, the Japanese government, and the US government) showed that radiation levels posed no short-term risk and only a minimal long-term risk. By comparison, news sources reported that nearly 50 patients died of exposure, dehydration, and other causes during hospital evacuations from the affected area. Similarly, the World Health Organization concluded in a 20-year follow-up study (http://www.who.int/mediacentre/news/releases/2005/pr38/en/index.html provides a summary statement and the report can be downloaded at http://www.who.int/ionizing_radiation/chernobyl/assessment_mitigation/en/index.html) that mental health issues – stemming in part from the forced evacuation of over 330,000 people – were by far the biggest health concern facing those removed from the exclusion zone. And to round out this discussion, it also makes sense to go indoors if an RDD goes off – to shelter from the radioactivity and to stay out of the way of the emergency responders (unless, of course, your building is on fire or is in danger of collapse).
There are many disasters for which evacuation makes sense – and the sooner the better. But for a radiological or nuclear accident it could be that our fight-or-flight reflex serves us badly. Sometimes sitting and doing nothing makes more sense – and saves lives.
Dr Y is a certified health physicist, trained in nuclear power plant design and operations, with experience in nuclear power, environmental science, and planning for radiological and nuclear emergencies. He has 30 years of experience in the areas of nuclear and radiation safety.