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This backgrounder is presented as part of the RADI-N2 Action Project. Click here to learn more!
Several factors affect how the human body reacts to radiation. These include the dosage (amount of radiation received), the time over which the dose is received, the cells that are affected, the part of the body that is affected, the type of radiation, as well as the age and general health of the person. The amount of radiation and the time over which is it received are the most important factors.
HIGH DOSE, SHORT TIME
High doses over short periods of time produce acute (severe), short-term effects. High doses tend to kill cells, which damages tissues and organs. This can lead to a whole body response called Acute Radiation Syndrome (ARS) which can end in death. People can be exposed to high doses of radiation as a result of catastrophic events (i.e., nuclear weapon explosions, nuclear reactor accidents) as well as in workplace accidents.
Even very high doses of radiation do not tend to result in immediate death, but can result in skin burns, hair loss, vomiting, sterility and cataracts (clouding of the lens of the eye).
LOW DOSE, LONG TIME
Low doses over long periods of time can produce chronic (long-term) effects. Low doses do not tend to cause immediate problems to tissues and organs, but over the long term they can lead to damage or alteration of the genetic code (DNA) in both gametes (reproductive cells) and somatic (non-reproductive) cells. DNA mutations in gametes can be inherited by offspring and cause abnormal growth or development. Mutations in somatic cells can cause cancer.
Radiation is an example of a physical carcinogen (cancer-causing agent). Many studies have linked cancer with occupational or accidental exposure to radiation. Some examples include lung cancer in uranium miners, skin cancer in radiologists, bone cancer in radium dial (glowing part in wrist watches) painters, and leukemia (blood cancer) in atomic bomb survivors. Radiation exposure to embryos in the uterus can lead to malformations and early childhood cancer. In all of these cases the radiation doses involved were well above the natural and human-made exposures that the average citizen routinely experiences.
Not all radiation may be dangerous. At the lowest doses of typical radiation exposure, from natural background levels up to hundreds of times this level, no health effects have been observed (long-term or short-term) despite intense scrutiny and many studies. There is even scientific evidence to suggest that radiation at these lowest levels may actually be beneficial, in a similar way that some chemical toxins are dangerous at high doses but beneficial at low doses (a phenomenon called hormesis).
A FINAL WORD
One important thing to keep in mind is that although ionizing radiation can cause DNA mutations, these mutations never result in any kind of amazing super powers like web-slinging or incredible strength. Very rarely, a DNA mutation will be beneficial for an organism (and it might even spread through a population via natural selection), but the advantage of the mutation is usually subtle – more like a slightly better enzyme than the ability to self-ignite. Lots of DNA mutations are neutral, with no advantages or disadvantages. However, many are lethal or harmful (i.e., carcinogenic), so it is a good idea to keep one’s exposure to ionizing radiation to a minimum level, commonly called As Low As Reasonably Achievable (ALARA). This is the official policy reflected in health regulations in Canada and other countries.