Before Going on to Radiation ...

Let's look at some common examples of where we see hormesis in humans.

• Vitamins and trace minerals clearly show the difference a dose makes. Arsenic and selenium were considered (and are) deadly poisons; but they have been found to be necessary nutrients.
• Some sunlight is necessary for production of vitamin D in the body, but too much leads to localized cancers, and in extreme cases, death.
• Some noises (such as waves) can be soothing and healthful, while long exposure to loud noises can cause mental confusion and loss of hearing function.
• Most athletes are well aware of "no pain, no gain"; too much pain, however, equals ruptured muscles, torn ligaments, and broken bones.
• Lack of stress in one's life (e.g., a deadline to complete a project) tends to make an individual lethargic, while too much stress can cause permanent physical and mental harm.

We'll be going on shortly to the specifics of radiation hormesis, but first, classes on the basics of ionizing radiation are getting underway in the next chapter.