Science: How to Avoid Radiation Without Really Knowing It

No normal man could freeze to death without first feeling the cold. None could fry without feeling the heat. But burning and freezing are ancient dangers, and nature has had plenty of time to evolve defenses. X rays and gamma rays are a subtler peril. Until recently, they were unimportant hazards in the human environment; evolution largely ignored them. Modern man can wander unheeding into strong radiation that he cannot feel, see, hear, smell or taste. And unless he carries an artificial radiation sense (a Geiger counter, ionization chamber, etc.), he may get a fatal dose without a suspicion of an alarm.

Radiation hazards are multiplying fast today, but Psychologist Edward L. Hunt of the U.S. Naval Radiological Defense Laboratory in San Francisco thinks that nature has not exhausted her defensive resources. He is sure that some higher animals—perhaps even man—have a latent radiation sense that might be trained to warn them against Atomic Age hazards.

Blue Flash. Scientists have known for decades, says Hunt, that the dark-adapted human eye can detect X rays and gamma rays as a yellow-green glow. This sensation apparently comes from direct action of the rays on minute light-sensitive cells in the eye's retina, but it has almost no value as a practical warning sense. When the eye is not darkadapted, and it hardly ever is, the retina is sensitive only to massive doses of radiation from such disasters as runaway nuclear reactors. On these unhappy occasions, the victim sees a vivid blue flash, and by that time certain death is only short hours away.

No other perception of radiation is known in humans, but eight years ago, Hunt and his associates, Donald J. Kimeldorf and John Garcia, found that rats will shun sweetened water, one of their favorite liquids, if they are dosed with radiation while they try to drink. This hardly proved that rats can sense radiation directly. Quite possibly they had been made slightly sick, associated their malaise with the sweetened water. But the hint seemed worth following.

After other encouraging but inconclusive experiments, Hunt & Co. trained batches of rats to sleep most of the time. This was not hard to do. If laboratory rats are put singly in small, comfortable pens and given plenty of food, water and light, they soon go to sleep. Ordinary noise does not usually wake them, and they do not mind wearing electrodes for measuring their heart action.

X Alarm Clock. When Hunt and crew had a rat sleeping peacefully, they recorded its heartbeats on an electrocardiograph (300-350 beats per min.). Then they squirted it with a beam of silent, invisible, 250,000-volt X rays. In about 12 sec., the rat woke up, sometimes going into a violent "state of alarm." Its heartbeat would speed up too. But if the radiation continued for long, the rat would go to sleep again, like a human grown accustomed to a steady night-time sound.

The scientists ran the experiment twelve times with different groups of rats. All were wakened within seconds by radiation too weak to hurt them. To make sure that the rats were not seeing the radiation as humans do with dark-adapted eyes, the scientists simply cut out some of the rats' eyes. But the surgically blinded rats woke up even faster than the others, as if their sensitivity had sharpened like the hearing and touch of a blinded man.