Coordinating risk assessments for radiation in outer space

In the next few decades, crewed missions to the moon and Mars will likely become frequent. One of the main challenges faced by these future missions will be the need to protect astronauts from the intense radiation of outer space.

Today, however, space agencies are taking different approaches to assessing the risks of this cosmic radiation, ultimately leading to a lack of consistency between their guidelines for radiation protection.

In a new editorial published in Journal of Medical Physics, researchers led by Werner Rühm at the Federal Office for Radiation Protection, Munich, Germany, review in detail existing radiation protection concepts relevant to human spaceflight, and how they are currently being enacted by different space agencies.

Rühm’s team (which was established by the International Commission on Radiological Protection (ICRP) with renowned experts from all over the world) hopes that by building on the team’s findings, space agencies will be able to develop a more harmonized approach to radiation risk assessments. This could in turn lead to more robust guidelines for protecting astronauts from cosmic radiation as they embark on extended interplanetary voyages.

Harmonizing guidelines

There are robust international guidelines for protecting workers and the public on Earth from the harmful effects of radiation. The same can’t be said for long-term crewed space missions, however.

This lack of harmonization exists “due to the complex and dynamic radiation environments, and an incomplete understanding of their biological consequences,” Rühm explains. “Because of this, space agencies follow somewhat different concepts to quantify radiation doses and their resulting health effects.”

Through their research, Rühm’s team aim to support space agencies in developing more coordinated guidelines for cosmic radiation protection that are consistent with the international guidelines already developed on Earth. In their editorial, the researchers review the inconsistencies of existing approaches to radiation protection through three accompanying papers.

Evaluating risk assessment

The first paper examines the risk assessments already put in place by various space agencies. As the paper shows, “very few space agencies consider the specificity of age and sex on how crew members respond to ionizing radiations in space,” Rühm explains. “Risk analysis can also be confounded by lifestyle factors that impact health.”

The second paper considers two different examples of periods where astronauts are exposed to high radiation levels: a 30-day voyage from Earth to the moon, and a 22-day stay on the moon’s surface, followed by eight days in free space. When these hypothetical missions were evaluated by the risk assessment measures currently used by five different space agencies, the study found significant differences in some of their estimates for the radiation experienced by the astronauts.

As Rühm further explains, this variation emerged since there were so many different factors for the space agencies to consider. “Their estimates could depend, for example, on considered dose quantity, the organs exposed to radiation, and protection from shielding,” he says.

The final paper reviews several different approaches to quantifying the risk of cancer in astronauts exposed to cosmic radiation. Since astronauts differ widely from the general population in (for example) their lifestyle, nutrition, and medical care, the study emphasizes that this risk can be incredibly difficult to calculate.

“This paper demonstrates the degree of variability in risk assessment, and discusses the usefulness of various risk metrics to quantify and communicate radiation-related risks to astronauts during spaceflight,” Rühm adds.

Guiding future missions

In identifying these existing limitations, the team is now hopeful that their review could inspire a new push to harmonize radiation risk assessments between international space agencies, which will be vital to beginning a new era of space exploration.

“Adventurous people have always tried to widen their horizon, this is part of our very nature as humans,” Rühm says. “Our work contributes to and supports one of the most exciting and challenging human endeavors ever undertaken.”