Comments of W. Alexander Williams
On the Draft ICRP report
Assessment of Radiation Exposure of Astronauts in Space
While there is much in the report I agree with, there are some serious problems that should be addressed. For the sake of brevity, I will point out several of these.
First, the report identifies that there are large uncertainties in estimating radiation exposure in space. I strongly agree with this. However, in its tables, graphs, and figures, the report does not specify the uncertainties in the data presented. Some data is presented in multiple significant figures, when, in my opinion, such precision is not warranted. I believe the cumulative uncertainty for estimates of radiation exposure in space is at least ±50%. The uncertainty might even be as much as a factor of ten (10). But I agree that the uncertainty is high and additional research is warranted.
Second, the report would seemingly endorse a risk estimate approach, rather than a dose estimate approach. This is contrary to all other ICRP publications, in which radiation assessments are based on dose. Similarly, career limits are not utilized in any other ICRP publications. These recommendations are a departure from other ICRP recommendations.
The usage of risk assessments is especially objectionable because it has a disparate impact on female astronauts. Women typically have a longer life expectancy than men, so a given dose will show a higher risk to women than to men. Does ICRP wish to endorse this practice? Even when it leads to disparate occupational opportunities for female astronauts? Even when, scientifically speaking, there are high uncertainties in the dose or risk assessment?
Similarly, risk assessment based on age results in differing occupational opportunities for younger versus older astronauts. Does ICRP wish to endorse this practice?
The report does not properly emphasize radiation risk in comparison to other risks faced by astronauts. Spacecraft are a form of experimental aircraft. From time to time, things go wrong. Through the years, the space programs of Russia and the USA have both had multiple accidents. Sadly, aerospace accidents are often fatal to astronauts. NASA’s “Astronaut Fact Book” shows a distinct pattern in the causes of death for deceased astronauts: There is a shockingly high rate of accidental death. These deaths are not just in on-the-job accidents; there are also accidental deaths during job-related travel and during private activities/hobbies. I believe the risks of being an astronaut are much higher than the risk of radiation exposure in space.
A far better radiation assessment and protection approach is one of full disclosure. I believe that astronauts would welcome a full disclosure of radiation dose, including the large uncertainties. These men and women are accepting significant risks from flying spacecraft. Surely they can make up their own minds regarding radiation concerns.