First it was food. Then drinking water. “Radiation from the Fukushima nuclear power station is now entering the food chain,” wrote one unnerved commentator.
It’s hard not to be spooked. This is radiation we’re talking about. Invisible. Odorless. Deadly. It can sicken and kill quickly, or inflict cancer years from now. And it has contaminated milk, seeped into spinach, and poisoned water. Of course people in Japan and around the world find this deeply disturbing. How could they not?
And yet the levels of radiation detected in Japanese food and water are so low it’s almost impossible to imagine them doing any harm. Yes, they often exceed regulatory safety standards — by as much as 17 times. Sounds scary. Where I live, the benchmark for tritium in drinking water is 7000 Bq per liter. If I were told the water coming out my faucet has tritium levels that are 17 times higher than government safety standards allow, I’d probably treat it like nuclear waste. But would that be reasonable? Not really. That’s because the standards are designed for chronic exposure and they are extremely cautious. If I drank that super-contaminated water every day for one year, the radiation I would be exposed to would be only one-half the amount of radiation we are all exposed to every year simply by living on planet earth. In a word, it would be trivial.
Calculations for the risks posed by contaminated food in Japan are similarly reassuring. That poisoned spinach? You’d need to stuff yourself with two pounds a day, every day, for one year, in order to raise your lifetime risk of contracting cancer by a whopping four per cent. (NPR has some more relax-and-breath perspective here.)
So why are so many people — in Japan and around the world — disturbed by reports of radiation contaminating food and water?
There are many factors at work. One is ignorance. News stories make a big deal about contamination being in excess of regulatory standards but they seldom explain that contamination in excess of the standards may not be dangerous in the slightest. More basically, lots of people simply do not know that exposure to radiation happens all the time, in man-made environments and nature. Eat vegetables? Then you’ve eaten trillions of radioactive uranium atoms absorbed from the soil. Got granite countertops? Bananas? There’s radiation in your kitchen. And it doesn’t take much to substantially increase exposure. Anyone who has flown in a plane, gone downhill skiing, or lived in a high-elevation city like Denver has done it.
But this is not all about facts and rational calculation. Indeed, that’s likely the least of it.
In the 1970s, when there was growing concern about nuclear power in the United States, nuclear engineers couldn’t understand why people were worried. “Look at the data,” they’d say. People would look at the data and go right on demanding the end of nuclear power. The engineers would respond by stamping their feet and insisting that people look at the data again.
This stand-off piqued the curiosity of psychologists. How do people judge risks? Why is there an apparent gap between perceptions and numbers? The investigation began.
One of the key insights of the last 40 years’ of research is that emotion matters far more than we realize. That might seem banal. Everyone knows that when you’re angry or in love your judgement can be skewed, sometimes unreasonably. But psychologists mean something different than that. The term of art is “affect.” Laypeople would call this “emotion” or “feeling” but these terms aren’t quite the same because we think feelings are something we experience consciously: If we sense no feelings, there are none. Thanks to much clever research, psychologists know better. Affect can be so subtle that we can even experience it without having the slightest conscious awareness of it.
In fact, it happens all the time. Look at this word: “radiation.” Feel anything? No, you say. But you almost certainly did. And given the cultural stigmatization of all things nuclear, the affect you experienced was almost certainly negative.
Affect has a profound influence on risk perceptions because we automatically and unconsciously use it as a way to measure risk: When something makes us feel good, our intuitive sense of the risk posed by that thing goes down; when something generates negative affect, the feeling of risk rises. (Conversely, good affect drives the sense of benefit from a substance or activity up while bad affect drives it down. Hence, risk and benefit tend to be inversely correlated in our perceptions, although not in reality.) Paul Slovic, one of the pioneers of the study of risk perception, dubbed this the “affect heuristic.”
So we hear about “radiation,” feel a chill, then use that feeling as a handy way to measure the risk. Conclusion: worry. Remember, this isn’t a conscious thought process. We may even deny that feelings play any role in our judgments and be offended by the suggestion that stigma and emotion make a difference. But they do.
That’s the big one, I think. But there’s another, more particular factor at work in the case of contaminated food and water. It’s the emotion of disgust and what is sometimes called the “law of contagion.”
In a series of famous experiments, psychologists Paul Rozin and Carol Nemeroff demonstrated that whatever triggers disgust repels us and no rational understanding can dispel that feeling. “When educated Americans refuse to eat chocolate shaped into realistic-looking dog feces, or refuse to eat a food touched by a sterilized cockroach, they are acutely aware that this “makes no sense,” yet acknowledge their feelings of aversion,” Rozin and Nemeroff wrote.
The “law of contagion” is related to disgust in that disgusting objects can transfer their “disgustingness” to other objects if they come into contact. As Rozin and Nemeroff showed in another series of fascinating experiments, the “law of contagion” has several key features: the transfer requires physical contact; once an object has been contaminated, it can not be decontaminated; and the contamination is “dose insensitive,” meaning even the slightest contact is enough to cause the transfer and make the object contaminated.
It’s obvious how this applies to the situation in Japan. Radiation is profoundly stigmatized. People are told food and water have come into contact with it. The repulsive feeling the radiation instils in them now transfers to the food and water. The levels of contamination simply don’t matter. The contagion has spread: The food and water are contaminated. People react the same way when told that a stigmatized synthetic chemical is present in something. That thing is contaminated. Quantity? Safe level? Irrelevant. It’s contaminated. Keep it away from me.
From a scientific perspective, this makes no sense. The first principle of toxicology is “the dose makes the poison,” after all. The level of contamination is not only relevant, it’s absolutely critical in determining what’s safe and what’s not.
The question then is why people’s intuitive responses are so out of whack with the scientific reality. The answer lies in evolution.
We instinctively recoil from contamination without the slightest regard for the extent of contamination because of what Paul Slovic calls “intuitive toxicology.” Is this water safe to drink? Is this meat safe to eat? How should we dispose of that corpse covered with purple dots? Our ancestors had to answer questions like these constantly. The only tools they had to assist them were their senses. And if you could see, smell, or taste fecal matter in the water — for example — then it was almost certainly present in sufficient quantities to make the water unsafe to drink. Hence, there’s no need to discriminate between “safe” and “unsafe” levels of contamination. Any contamination is dangerous. Stay away.
The world has changed in many ways. Today, we can detect substances in parts per billion, even parts per trillion. We know there are carcinogenic chemicals in the steam rising from my cup of coffee. We know there may be radioactive uranium atoms in even the freshest, cleanest, most organic spinach.
What hasn’t changed is our intuitive sense of contamination. And that mismatch between ancient hardwiring and modern technology is a big reason why we have seen such an overreaction to the news from Japan.