Space is a harsh environment for humans. Instead of being protected by an atmosphere, like on Earth, humans are exposed to radiation that can, in the long-term, increase their risk for cancer. Now, scientists are taking a closer look at space radiation and how best to control astronaut cancer risk.
In order to find about cancer risk on Earth, researchers usually note the levels of radiation exposure and then later, cancer development in large populations of people. For example, survivors of Hiroshima and the Nagasaki atomic bombings could be looked at after their exposure. This, in turn, gave researchers an idea of how much a dose will increase cancer risk.
With that said, calculating the risk from radiation in space is a lot different. Space radiation is actually different from radiation on Earth; the worst component of it, in particular, is HZE ions. These ions are composed of atomic nuclei that are stripped of their electrons. They move through space at near the speed of light and can actually move through aluminum or even through an astronaut, leaving ionization tracks. On Earth, these HZE ions are deflected by the planet's atmosphere.
While it's a good thing that Earth deflects this radiation, it also means that there's no way to measure its effects on Earth. With that said, there are particle accelerators that can, in theory, simulate the types of radiation that's found in space.
Unfortunately, there's increasing evidence that HZE ions are good at causing cancer, and the types of cancer that they cause tend to be more aggressive than their counterparts on Earth. When mice were hit with HZE ions, most of the liver tumors that were developed went on to metastasize to the lung. This, in turn, implies that it's a more aggressive type of liver cancer.
The current goal for the research is to more accurately calculate cancer risk for astronauts. In addition, researchers hope to find a better understanding of how exactly HZE ions cause cancer in the first place. This, in turn, could help researchers develop a way to potentially lower this cancer risk or even prevent it.
The findings will be important for long-term space missions, and they could have a major impact when it comes to sending a human to Mars.
The study was published in the Feb. 22 issue of the journal Frontiers in Oncology.
