While we are getting better at seeing radiation’s effects on individual cells, it remains difficult to predict the effect of any particular dose on a population. The conventional wisdom regarding what happens to people at exposures below 100 millisieverts has been essentially conjecture; many experts think exposures in that zone pose no harm. But epidemiological studies show there is wide variation in people’s sensitivity to radiation: for example, at 100 millisieverts — a tenth of the dose causing outright radiation sickness — women have about a third higher risk for cancer.
Radiation can trigger the formation of oxygen compounds known as free radicals in the cytoplasm surrounding the nucleus and induce gene mutations inside the nucleus, even in cells that haven’t been directly hit. Cancer is not the only possible result; the use of radiation as a cancer treatment has made it clear that such therapy increases the risk of cardiovascular disease. There are also hints that radiation may contribute to endocrine, metabolic, and nervous system disorders.ers of solid organs than men, whereas men are significantly more at risk for leukemia, according to the National Academy of Sciences committee that is charged with recommending protection measures.
Diet, chemical exposures, and other influences may alter epigenetic patterns and lead to disease. There is ample evidence that radiation affects epigenetic processes. For example, Alexandra Miller of the Armed Forces Radiobiology Research Institute in Bethesda, Maryland, has done extensive work on uranium toxicity, including on depleted uranium. In research published in 2005, Miller exposed mice to depleted uranium and tracked the incidence of leukemia by looking at their spleens, where blood cells develop. The spleen cells showed reduced DNA methylation, an important epigenetic regulator implicated in many cancers when it goes off track. And epigenetic effects may be just as important in reproduction as the genes themselves; a maladaptive epigenetic pattern may transmit disease or at least its susceptibility to future generations.
This section is for those of you who have asked: I am adopted why am I sick??
Mothersill’s research team demonstrated bystander communication not just between cells but also between organisms. In experiments conducted in 2006, Mothersill irradiated a group of rainbow trout in a laboratory tank, then added nonirradiated trout. In a second experiment, she irradiated a group of fish, then removed them from the tank and replaced them with healthy, nonexposed fish. In both experiments, the nonirradiated fish displayed bystander effects from radiation.
This “medium transfer” seems spooky — or was it simply a chemical left in the water by the zapped trout? This is plausible, since cells are well known to be chatty, using many different chemicals to exchange information about and respond to the environment, often as a group. With the bystander effect, scientists don’t yet know how the information is transmitted, but it is likely to be consistent with other evidence of complex cell signaling.
If we were all Reference Man, perhaps our robustness would allow us to disregard low-dose risks. But we’re not; we’re flawed, vulnerable individuals. The human environment and myriad products we use every day expose us to hundreds of chemicals that disrupt biological processes and whose cumulative consequences are poorly understood. Radiation is another wild card added to the mix, potentially affecting everything from allergies to procreation, and little is known about how it interacts with these other influences.