Radiation Protection Standards

At the start of the twentieth century it became clear that standards would have to be set in order to protect workers and patients from the negative effects of exposure to radiation. First attempts at protecting people created the concept of tolerable doses.  Tolerable doses are those below which no immediate effects occur. Though at first it seemed to do enough, in 1948 the National Council on Radiation Protection (NCRP) introduced permissible doses. These doses differed from tolerable doses in that they were not expected to cause harm during a person’s lifetime and not just the days following initial exposure.

Today, we understand that low-level radiation exposure can lead to stochastic effects, or effects that though they may be predicted statistically, occur spontaneously. Due to these stochastic effects, modern radiation standards are based on probabilistic assessments of radiation effects.

These modern standards are based on the idea that a high standard of safety for a work environment means that no more that 100 per million workers die in a year. To put it in perspective, in a workforce of 100 people, 1 person would die every 100 years. But, this was not considered safe enough so an acceptable risk of 50 deaths per million workers per year. This translates to 1 person every 200 years in a 100-person workforce.

After this definition of “safe” was set, statisticians did a whole bunch of math (that was overly safe and assumed people worked in the industry for 40 years and radiation effects built up and 10 percent of people would reach maximum dosage and blah blah blah) ultimately deciding that a “safe” whole-body dose-equivalent limit for stochastic effects was set for workers was set at 5 rem per year. Then, they released this limit to the industry, and the industry more or less uniformly decided that in order to stay super safe, they would use a limit far below that, and most companies set their own limit at 1 rem per year. The NCRP also calculated the dose limit to the individual members of the public, 0.5 rem per year. Once again, the industry set a standard below this to prevent crossing that line.

Again, these limits were set for stochastic effects so what they’re preventing is lifetime risk not just immediate harm. I guess what I’m saying is, the exposure limits are there to keep people super safe.