This applies to radiation as well. X-rays are important to see what is happening inside our bodies from injury or disease. However, too much radiation exposure causes more harm than its worth. For example, dental x-rays are important when you have a big problem, but I have "great teeth" according to my dentist. So I resist the yearly dental x-rays and opt for every 2-2 1/2 years. I don't want the extra radiation no matter how small the dose. (I grew up in Nevada, I probably have my share and more.)
In fact, the American Dental Association guidelines state "adults, who have regular check-ups and are free of signs/symptoms of oral disease, are at a low risk for dental caries. Nevertheless, consideration should be given to the fact that caries risk can vary over time as risk factors change. Advancing age and changes in diet, medical history and periodontal status may increase the risk for dental caries.
A radiographic examination consisting of posterior bite wings is recommended at intervals of 24 to 36 months."
So, if you want to glow a little less brightly and your dental health is great, just tell the hygienist you'll pass on the yearly x-rays. (I NEVER miss those cutting plastic bite wings!) She may or may not frown and look at you like you're a health nut, but it's worth it. Go science!