Space radiation may increase risk of cancer

Using mice and models, scientists have concluded that humans who spend long periods in space, exposed to its radiation, will have a 3% higher risk for cancer.

A team led by researchers at Colorado State University and Frederick National Laboratory for Cancer Research, which is part of the National Institutes for Health, used a novel approach to test assumptions in a model used by NASA to predict these health risks. Based on the NASA model, the team found that astronauts will have more than a three percent risk of dying of cancer from the radiation exposures they will receive on a Mars mission. That level of risk exceeds what is considered acceptable. [emphasis mine]

And how did they come to this conclusion?

…For the study, Weil and first author Dr. Elijah Edmondson, a veterinary pathologist and researcher based at the Frederick National Laboratory for Cancer Research in Maryland, used a unique stock of genetically diverse mice, mimicking a human population. Mice were divided into three groups with the first group receiving no radiation exposure and the other two receiving varying levels of exposure.

Edmondson, who conducted the research while completing a veterinary residency in pathology at CSU, said that for this type of research project, genetic variability is crucial. “Humans are very genetically diverse,” he explained. “You want to model that when it’s appropriate and feasible to do so.”

Weil said although the research team saw different tumor types, similar to humans, but the heavy ions did not cause any unique types of cancer. They also saw differences by sex. In humans, women are more susceptible to radiation-induced cancers than men; one of the main reasons is that women live longer, allowing sufficient time for cancer to develop. In assessing the cancer risk between male and female mice in the study, scientists said the findings parallel human data.

Edmondson said the study validates the NASA model to measure cancer risks for humans from space radiation.

In a sense, this study is junk. First, it discovers the obvious (radiation increases your chances of getting cancer). Second, it is too model-dependent, so assigning any precise percentage to that increase in humans is absurd, especially when based on a sample comprised of mice.

Third, and most important, it completely forgets the reality that life is risk, exploration is dangerous, and to do great things you need to take greater chances. That NASA concludes these questionable numbers are unacceptable means that NASA will never send humans anywhere beyond Earth orbit. Ever.

Study says space radiation less of a risk

A newly released study now claims that, based on a long term review of astronauts who have spent a considerable time in space, it appears that space radiation does not cause an increase in cancer later in life.

The new study analyzed information from 418 space travelers, including 301 NASA astronauts who had traveled to space at least once since 1959, and 117 Russian or Soviet cosmonauts who had traveled to space at least once since 1961. These participants were followed for about 25 years, on average.

During this time, 89 of the participants died. Among the 53 NASA astronauts who died, 30% died from cancer and 15% from heart disease; while among the 36 Russian or Soviet cosmonauts who died, 50% died from heart disease and 28% from cancer.

The researchers used a special statistical technique to determine whether deaths from cancer and heart disease likely had a common cause — in this case, the common cause would be space radiation. But their results did not point to a common cause of death. “If ionizing radiation is impacting the risk of death due to cancer and cardiovascular disease, the effect is not dramatic,” the authors wrote in their study, published July 4 in the journal Scientific Reports.

This story first appeared about two weeks ago, but I didn’t think it significant, and still don’t. The sample is just not large enough to draw any solid conclusions. Moreover, this is exposure in low Earth orbit, not on interplanetary missions where the radiation risk is higher. It would be a big mistake for future space engineering to accept these findings blindly.

Still, news reports keep popping up about it, and I decided I should at least note it here on Behind the Black.