Answer to Question #627 Submitted to "Ask the Experts"

Q

How would solar flare radiation have affected the astronauts of the Apollo missions while travelling to and walking on the moon?

A

During the past 30 years, several committees of the National Council on Radiation Protection and Measurements (NCRP) have evaluated the potential health-related effects which would be caused if a significant solar particle "storm" should occur during various activities performed by astronauts, including lunar or Mars missions.

In a report issued in 1989, the NCRP estimated that if a major solar particle event occurred during a visit to the moon, it could give the astronauts doses to their skin of 6 Sv (600 rem) with bone marrow doses of close to 0.9 Sv (90 rem). Although the radiation exposure would not be life threatening, it would likely have consequences for both the long-term and short-term health of the astronaut. A skin exposure of that magnitude has a probability of about 50% of causing visible reddening ("erythema"), with an increased risk of skin cancer in later years because of damage to the dermis. It is likely that the astronauts would temporarily lose all of their hair. The deep dose to the blood-forming organs would result in blood-count changes that would be detectable in lab studies, but probably would not have significant clinical consequences during the mission. Temporary sterility (10-20 months) would most likely occur for male astronauts.

It is also generally accepted that there is an increased risk of cancer as a result of a whole-body radiation exposure of this intensity. It should be noted that the current maximum recommended dose for astronauts is under review by the NCRP. For males, it had been set at a lifetime cumulative maximum of 4 Sv (400 rem), a value which is predicted to lead to an increased cancer risk of 3% over that of the general public.

Robert J. Barish, PhD, CHP, DABR, DABMP, FAAPM