I was recently at the dentist for a check-up and they had a chart on the wall, kind of like this one here. In short it tells you how much radiation you’re exposed to when you engage in different activities. For example flying from New York to Los Angeles exposes you to about the same amount of radiation as eight dental X-rays. Believe it or not, flying exposes you to an increased amount of radiation coming from space. A single flight across the ocean is no big deal but long-term elevated radiation exposure can increase your risk of some kinds of cancer, and it’s why workers that are exposed to elevated levels of things like X-rays are monitored to make sure exposure is kept to a minimum.
It got me thinking, while I listened to the slow and steady suction of spit from my oral cavity, “I wonder if Lois Lane, would have to wear a radiation safety badge?” I am totally unsure about the radiation output of Superman’s X-ray vision, but there must be a certain repetitive amount of exposure she is getting, vis-a-vis Clark Kent. It’s got me wondering if Superman’s secret identity is necessary to limit Mr. Kent’s legal liability. I mean the workers compensation claims alone at the Daily Planet, if his true identity were known, would be off the charts. They would need to give employees access to lead-lined vests, to have Mr. Kent continue working there. That’s as far as I made it with this line of thought before, I spit, got my toothbrush and was told I need to floss more.
Having left with an infinitesimal increase in my annual level of radiation exposure has not caused me to lose sleep. Animal cells have ways of repairing damage caused by ionizing radiation. In the event the damage can’t be repaired, individual cells can self-destruct, leaving healthy cells to fill the void. As long as your ability to repair damage exceeds the rate of repair you should be fine. Its when damage accumulates when the fun starts … and by fun I mean awfulness.
This awfulness aside, X-rays can be incredibly useful. The discovery of X-rays was quite by accident. The German physicist Wilhelm Röntgen was trying to pass an electric current through gases at a low pressure which were known as Crookes tubes. He realized that the tube was capable of illuminating a screen covered with a chemical compound known as platinobarium. This illumination persisted even when it was held nine feet away and the tube was covered in cardboard. He assumed that this illumination was due to some unknown radiation “X.” Röntgen spent some time testing which materials would permit these rays to pass through them. Below is an example of one of those experiments, where Röntgen has collected an image of his wife’s hand. As you can see these rays passed readily through soft tissues but bones and metals not so much. When Röntgen publically presented his work in 1896, it generated a great deal of interest. Eventually the screens for imaging and what came to be known as “X-ray tubes” became available to allow people to take “bone portraits.” These were just as fun as they were carcinogenic. Fortunately, physicians, also, immediately realized the value of such imaging, and by 1896, started using the technique to look at the human skeleton. Röntgen went on to win the Nobel Prize in 1901.
Shortly after X-ray usage became more common, physicians began to realize the drawbacks of their use. A German physician by the name of Émil Grubbé got horrible burns on the back of hand by repetitively X-raying his left hand. After consulting with colleagues he concluded that X-rays may be damaging to human tissues.
Now the use of X-rays for imaging bones might seem like the only real purpose of X-rays, but the damage wrecked can also be used productively. For example, In the 1940’s, it was becoming apparent that genetic recombination between bacterial strains was possible. Joshua Lederberg and Edward Tatum had found that when a culture of E coli was treated with radiation from sources like X-rays, some colonies were isolated that would grow in a complex mix of nutrients but would not grow on minimal medium (to learn more consult my last blog post). It was found that, just by adding back a single nutrient, growth could be restored in minimal media. When two different mutants were grown together and then plated on minimal media, a few colonies appeared. This meant that bacteria could readily swap genetic material, much like humans do when they have sex. This type of bacterial “sex” is knows as conjugation. If you want to see microscopic images, I recommend you google “sex pilus” for some hot bacteria-on-bacteria action. For their work on bacterial conjugation, Tatum and Ledeberg would win a Nobel Prize along with George Beadle.
Radiation is one of those things we live with everyday. It is useful … it is harmful … it is fact of life. That said, I still think someone should talk to Lois Lane about her boyfriend. Or at the very least send Clark Kent to my dentist. I think they have chart that he should look at.