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radiation, even low-level background radiation, can potentially cause
damage. Scientists use the term millirem to describe a person’s
exposure to radiation. A person living in the United States receives
about 360 millirem per year. Approximately 60 millirem comes from
medical procedures and 300 millirem comes from natural sources of
radiation. If you live near the Rocky Mountains, you would receive roughly 40 millirem per year from terrestrial radiation. If you happen to live on the Atlantic Coast, you would receive about 55 millirem per year. There are many factors that can increase a person’s exposure to radiation. For example, a businessperson that travels from New York to California a few times a month will have a higher exposure than one who drives a car. (A coast-to-coast roundtrip airplane ride exposure is 5 millirem.) Another example would be if a person is in an automobile accident and has to have X-rays. If the doctor orders the patient to have a chest X-ray (8 millirem), a head/neck X-ray (20 millirem), and a lumbar spine X-ray (130 millirem), the patient would ultimately have more exposure than if he had not been in the accident. Through research, scientists have found how much radiation a person can be exposed to before symptoms appear. Different human cells respond in a variety of ways when exposed to radiation. Some may be able to repair themselves, some may begin to reproduce in an unusual way, or some may die as a result of their exposure. When a cell starts to replicate in an altered form, this is called a mutation. A mutation can be caused when a cell’s DNA is has been hit by radiation. An example of this would be constant, unprotected exposure to the sun can cause mutations in the skin’s cells leading to melanoma (skin cancer). Please see “Do you want the Recipe” for more information on DNA* Sometimes, people are exposed to high doses of radiation over a short period of time. These events could be man-made such as a nuclear bomb, or a natural event such as a solar particle event. In cases where the whole body exposure rate is up to 100 rems, human cells might lose their ability to do their jobs. At exposures greater than 100 rem, a person may get radiation sickness. These symptoms are flu-like in nature: diarrhea, nausea, and vomiting. At doses greater than 300 rem, the body’s disease fighting immune system could become damaged. Fifty percent of the people exposed to doses greater than 400 rems at one time, might die within 60 days, if a doctor does not treat them. If you are interested in learning other exposure facts, refer to the table below.
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