Deep-Space Travel Could Create Cardiac Problems for Astronauts

Exposure to cosmic radiation outside of the Earth's magnetic field could be detrimental to astronauts participating in long-term manned missions, according to a new study.

Researchers at the University of Alabama (UAB; Birmingham, USA) examined the effect of iron ions (⁵⁶Fe)--a particularly damaging component of cosmic radiation—in an animal model, targeting specific arterial sites in male apolipoprotein E-deficient mice. They then analyzed the mice at 13 and 40 weeks afterward to assess the development of atherosclerosis in the aorta and carotid arteries.

The researchers found that ⁵⁶Fe radiation accelerated the development of atherosclerosis in irradiated portions of the aorta, independent of any systemic effects on plasma lipid profiles or circulating leukocytes. Further, the radiation exposure resulted in a more rapid progression of advanced aortic root lesions, characterized by larger necrotic cores associated with greater numbers of apoptotic macrophages and reduced lesional collagen, when compared to sham-treated mice; intima media thickening of the carotid arteries was also exacerbated. The researchers concluded that the potential consequences of radiation exposure for astronauts on prolonged deep-space missions are a major concern. The study was published early online on April 6, 2011, in Radiation Research.

"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 coauthor Janusz Kabarowski, PhD, an assistant professor in the UAB department of microbiology. "The irradiation had no significant effect on the frequency of circulating immune and inflammatory white blood cells or plasma lipid profile.”

"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,” added coauthor Dennis Kucik, MD, PhD, an 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.”

Accelerated ions in cosmic radiation interact differently with objects and people. While X-rays can be blocked by lead shields, cosmic radiation ions can become more dangerous when they interact with metals, generating secondary particles that also may have biological effects. In addition, while it is possible to use other materials to shield against ion radiation, incorporating these into spacesuits presents significant challenges.

Related Links:
University of Alabama