If children are exposed to X-rays while still in the mother’s womb (in utero), their risk of all cancers increases by 40 percent, of tumors of the nervous system by 50 percent, and of leukemia by 70 percent. Today there are thousands of people with damaged thyroid glands, many of them with cancer, who were radiated with X-rays on the head, neck, shoulder or upper chest 20-30 years ago. Ten X-ray exposures at the dentist’s office are sufficient to produce cancer of the thyroid. Multiple X-rays have been linked with multiple myeloma – a form of bone marrow cancer.
A chest x-ray results in a dose equivalent of about 10 millirem; a mammogram about 200-300 millirem; an abdominal examination about 400 millirem); and a CT examination (computed tomography, also called "CAT scan"), between 2,000 and 10,000 millirem.
When radiation therapy is used to treat cancer, a very large dose of radiation, about 5,000,000 millirem (or 5,000 rem) is delivered to the tumor site. Below is a chart that says that each dose of radiation treatment delivers 2,000,000 millirem so with the multiple treatments most patients receive it is easy to see how fast they get up to a near fatal dose. Ten thousand mSv is a fatal dose. That is 10,000,000 millirem.
Perhaps the best way to understand this is to compare it with natural radiation — the 15,000 particles from natural sources that strike us each second throughout life. One millirem of exposure corresponds to being struck by approximately 7 billion particles of radiation. Do the math if you have a calculator that goes up that high. That is five to ten million mrem multiplied by 7 billion particles slamming into patients during their radiation treatments.
We are constantly bombarded from above by cosmic rays showering down on us from outer space, hitting us with 30 mrem per year. Combined with other natural source we are all exposed a total average dose of about 85 mrem per year from natural sources, or 1 mrem every 4 days.
Hydrogen would be indicated for such exposure and that is why it is suggested to drink plenty of highly concentrated hydrogen water when one travels at high altitudes in jet planes. NASA will want to completely investigate hydrogen to protect space travelers on long journeys.