Space travel could kill you

EXPOSURE TO COSMIC RADIATION outside the Earth’s magnetic field could be detrimental to astronauts’ arteries, according to a study by University of Alabama at Birmingham (UAB) researchers.

Using mice as test animals, researchers assessed the affect of iron ion radiation commonly found in outer space to see if exposures promoted the development of atherosclerosis, as terrestrial sources of radiation are known to do.

They found it accelerated the development of atherosclerosis, independent of the cholesterol levels or circulating white blood cells of the mice. It also worsened existing atherosclerotic lesions.

“It’s well known that prolonged exposure to radiation sources here on Earth, including those used in cancer treatment, excessive occupational exposure and atomic bombs, are associated with an increased risk for atherosclerosis,” said Dennis Kucik, associate professor in the UAB Department of Pathology.

“But cosmic radiation is very different from X-rays and other radiation found on Earth. The radiation risks of deep-space travel are difficult to predict, largely because so few people have been exposed.”

Apollo astronaut

Only 27 Apollo astronauts have travelled beyond Earth's protective magnetic field.

Irreversible damage

X-rays can be blocked by lead shields. But cosmic radiation ions can become more dangerous when they interact with metals, generating secondary particles that also may have biological effects.

Although it’s possible to use other materials to shield against ion radiation, incorporating these into spacesuits presents significant challenges.

The only people who’ve been exposed to high levels of cosmic radiation are the 27 Apollo astronauts who travelled as far as the Moon in the late 1960s and early 1970s.

Kucik said that because many people have early atherosclerosis—whether they travel in space or not—they could not draw any conclusions from the small number of astronauts who have been outside the Earth’s magnetic field.

Instead, they examined atherosclerosis development in mice following targeted exposure to a particle beam of high-velocity iron ions—similar to those found in space.

They tested the mice after 13 and 40 weeks to assess the development of atherosclerosis in the aorta and carotid arteries. They concluded there was a biological response to radiation injury.

“At 13 weeks it was surprising and quite remarkable that we already could see permanent damage—an irreversible thickening of the artery wall where it had been exposed to radiation,” said co-author Janusz Kabarowski, assistant professor in the UAB Department of Microbiology.

Artist's impression of a mission to Mars

Astronauts on future manned missions to Mars will need to be protected from deadly radiation.

Potential cancer spin-off

Knowing the effects of cosmic radiation on the heart health of deep-space astronauts will help meet the unique challenges of treatment and prevention posed by missions of long duration, Kabarowski said.

“Our future research will look at the mechanisms causing the damage, and we will try to find a way to target those mechanisms to correct the damage or prevent it altogether.”

Kucik said the team’s findings also may help cancer treatment. Newer proton radiation therapies can be targeted to stop and deposit all of their energy in a tumour, much like iron ions from space stop in the body.

“No one knows the atherosclerotic risk of this therapy,” Kucik said. “Anything we learn through these studies on deep-space travel will be useful for cancer patients.”

The research has been published online in the journal Radiation Research.

Adapted from information issued by Jennifer Lollar, University of Alabama. Images courtesy NASA / Pat Rawlings (SAIC).

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