Excessive exposure to harmful solar radiation is a career hazard for astronauts who are at risk of developing cancer and heart disease as a result. At least that's what we thought. New research shows that astronauts do not die prematurely, but scientists warn that long-term missions pose a serious risk.
A study published today in Scientific Reports could not associate exposure to space radiation with an increased risk of death from cancer or cardiovascular disease among astronauts and cosmonauts. It is a surprising, if not encouraging, finding it was long anticipated that the exposure to harmful ionizing radiation would later afflict the astronauts in the form of disease and possibly an early grave.
The lead author of the new study, Robert Reynolds of Mortality Research & Consulting, Inc. of California, however, warned that longer missions that are further away from Earth's protective magnetic field, such as a mission to Mars, are likely to be dangerous and dangerous possibly shorten life.
For the new study, Reynolds and his colleagues conducted a statistical analysis of publicly available historical data. A total of 418 spacemen were included in the study, including 301 astronauts and 117 cosmonauts.
The study took into account all NASA astronauts since 1959 and all Soviet or Russian cosmonauts since 1961, all of whom experienced spaceflight astronauts before July 2018 and cosmonauts in December 2017. The average follow-up time for astronauts was 24 years and for cosmonauts 25 years.
A total of 89 deaths were recorded, including 53 astronauts and 36 cosmonauts. These individuals died for a variety of reasons, but Reynolds and his team were only interested in two specific causes of death: cancer and cardiovascular disease, as these conditions may be related to radiation exposure. Among astronauts, 30 percent died from cancer and less than 15 percent from heart disease. For the cosmonauts, half of whom died from heart disease and 28 percent from cancer, the statistics were slightly different.
"When ionizing radiation affects the risk of death from cancer and cardiovascular disease, the effect is not dramatic."  These statistics may seem both high and alarming, but Reynolds's analysis showed that these numbers were nothing out of the ordinary. In the data indicating a common cause of death, namely radiation exposure, no trend or hiccup could be detected. "When ionizing radiation affects the risk of death from cancer and cardiovascular disease, the effect is not dramatic," the authors of the new study concluded.
However, these are "historical doses of space radiation," as the authors have described. Apart from the Apollo missions, astronauts and cosmonauts in Earth's orbit were still protected by the earth's magnetic field. The situation in the future as astronauts advance deeper into space will be significantly different, as stated in the new study:
It is important to note that future space exploration missions are likely to provide much greater levels of space radiation than have historical doses that lead to a different risk profile for future astronauts and cosmonauts. In the coming years, it is imperative that epidemiologists continue to study the astronaut and cosmonaut populations for possible adverse effects of exposure to space radiation using both novel and known methods. Doing so is an essential part of supporting human ambitions for further exploration and eventual colonization of our solar system.
Unfortunately, a mission to Mars could shorten a person's life by years, unless shielding or special spacesuits are developed. 2013 NASA research showed that astronauts on Mars would be irradiated about once a week by the radiation of a full-body CT scan for a full year for a full year without adequate protection.
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A return trip to Mars would therefore expose astronauts to two-thirds of the permissible life-long exposure. And that does not include time on the Martian surface, with its pathetically thin atmosphere and weak magnetic field.
The new research is encouraging for astronauts entering orbit near Earth, but given our desire to venture beyond that, we will need to develop some viable solutions.