Example

Dress Rehearsal

There are lots of good things in the world that, taken to extremes, can turn out to be bad. Ice cream and doughnuts come to mind, as well as television, video games, and even overdoing it on studying and exercise can be bad for you (Don’t tell your teachers we said that). In chemistry class, you’ve been studying the concept of radiation. Radiation is defined as the emission and propagation of energy in the form of waves, rays, or particles. Radiation is helpful in the medical and scientific fields, but because radiation can ionize matter with which it collides producing unpaired electrons, too much can be dangerous to humans.

Atoms or molecules that have unpaired electrons are called free radicals. We don’t mean the New Radicals from the 90s; we mean free radicals that can affect other molecules and cause normal cells to become abnormal. This hampers the proper functioning of cells, systems, and organs. The damage produced by radiation is dependent upon the type, amount, and power of the radiation, the kind of tissue being affected, and the distance from the source of radiation.

We are normally subjected to radiation in everyday living, from x-rays to air travel, and from the air to the cosmos. Annual radiation exposure that appears to have little effect on us ranges from about 0.1 to 0.3 rems of high-energy radiation. Intense, short-term radiation, however, can have bummer effects.

Your text indicates the following exposure rates and their effects: A dose of 0-25 rems has no detectable effects on humans. Increasing the dose to 25-50 rems causes a temporary decrease in white blood cell counts. A larger dose of 100-200 rems causes nausea and a significant decrease in white blood cell counts. Finally, an exposure to 500 rems results in a 50% chance of death within 30 days of exposure. Not a pretty picture any way you look at it.

Not only does the amount of radiation determine the intensity of effects, distance from the source does, too. Naturally, the farther a person is from the source of radiation, the less the intensity, so STAY AWAY!

Your text does an admirable job of explaining the concepts and effects of radiation, but to see how this works in real life, take a look at the disastrous earthquake in Japan in 2011 as reported by AOL News service. Nuclear plants were damaged, resulting in the escape of radioactive particles into the air. Persons living within 20 miles of the Fukushima Dai-ichi plant were forced to evacuate their homes. Radiation levels recorded in Tokyo, some 175 miles away, were said to be 20 times the normal amount. Here, distance determined the intensity of radiation levels; the farther from the source (the plant), the less danger to people in the area.

Physicians involved in the disaster confirm what your textbook tells you. The first signs of radiation sickness are nausea and vomiting, followed by reddening skin, bleeding gums, and hair loss. Higher exposures can cause cancer and death due to cellular changes in the body. Radiation levels at the plant were measured at 40 rems, well above the recommended limit of 5 rems annually for plant workers. Many workers continued to be exposed to daily, high dosages as they tried to shut down the plants. The amount of the exposure will have a definite effect on the health of the workers.

Whoa, not so fast, say scientists studying the effects of another nuclear disaster at Chernobyl. While these experts interviewed in an article for Scientific American don’t wish to minimize the effects of high levels of exposure to radiation, they argue that other factors are active. They maintain that measurements of radiation might not be accurate. Also, only a handful of studies have connected high levels of radiation to disease.

They admit that radiation probably causes an increase in the incidence of thyroid cancer in children. They also concede that two other effects have been an increase leukemia cases and the development of cataracts, yet they also turn to other factors that might be responsible for those health concerns. One factor is stress. You know all about THAT! They also point out that the elderly, who were allowed to return to their homes previously evacuated because of their close location to the plant, lived longer than those who did not.

This conflicting evidence can only be resolved through more research, the following of future generations of families exposed to intense radiation.

By synthesizing all this information from different resources, you might conclude that the study of radiation needs, well, more study. While all scientists agree that high levels of ionizing radiation can be dangerous to the human body, exactly what the long-term effects might be is a point of disagreement. This can only be solved through time and study. Carry on, young investigator.

Sources:

Buthelezi, Thandi, et al. Chemistry: Matter and Change. New York: McGraw Hill, 2008.

Choi, Charles Q. “Radiation's Complications: Pinning Health Problems on a Nuclear Disaster Isn't So Easy.” Scientific American. 16 March 2011. Scientific American, Inc. 5 May 2012. .

Gay, Mara. “5 reasons Radiation Exposure in Japan May Be Worse than You Thought.” AOL News. 15 March 2011. AOL News. 5 May 2012. .

That’s a Wrap

Your students have examined three sources of information about the effects of radiation: a textbook, a news article, and a scientific journal article. They have brought together commonalities among the three sources as well as disparities, reviewing data and statistics in order to draw conclusions and taking note of when further investigation is needed. They’re getting so good at this, it’s almost like they don’t need you anymore.

Quiz Questions