Radiation Primer

Radiation is scary, isn’t it? We can’t see it and we can’t feel ourselves being exposed, but we know it can cause cancer. In order to make sense of this complex environmental hazard and perhaps dispel some of the fear surrounding it, below is a ‘radiation primer.’

Radiation comes in many forms, most of it harmless. One way to look at radiation is to divide it into two forms: ionizing and non-ionizing. Non-ionizing radiation is the less harmful of the two and is the kind given off by microwave ovens and cell phones. Ionizing radiation, on the other hand, causes atoms to change their structure by becoming “ionized.” This is the more dangerous type of radiation and comes in the form of gamma rays, beta particles, and alpha particles. Alpha particles are not able to penetrate the skin but are dangerous if inhaled. Beta particles from some sources can be blocked by clothing, others require a thin layer of metal or plastic. Gamma radiation can either pass through the body or can lodge in the bones. You are exposed to radiation by breathing or eating radioactive substances, or from nearby radioactive substances that release gamma.

The typical American is exposed to about 300 millirem of ionizing radiation per year from background sources. About half of our background radiation exposure is from radon in building materials and in the ground. We also receive radiation from cosmic rays (more when you’re up in a airplane) and from foods and even minerals present in the human body. The average American also receives an additional 350 millirem from medical X-rays, other nuclear medicine procedures, home appliances, and living near nuclear power plants.

Many other countries use the international unit Sievert to express radiation dose. Converting Sieverts to rems is easy. One sievert equals 100 rem. One milliSievert equals one hundred millirems (1 mSv = 100 mrems).

Exposure to ionizing radiation causes problems with cells in the body that are constantly turning over: blood cells, the bone marrow, sperm and eggs, and cells lining the stomach and intestines. The growing fetus is also extremely susceptible. Health effects from radiation range from mild skin burns to rapid death. Long-term low dose exposure can cause cancer and gene mutations that can be passed on to children. Radiation sickness is caused by higher one-time exposures, and the severity of effect depends on the dose, or amount, of radiation. Symptoms include nausea, weakness, hair loss, skin burns or diminished organ function. Most regulatory agencies consider it safe to receive up to 100 millirem of radiation per year beyond background, the equivalent of approximately 10 x-rays.

In pregnancy, the fetus is most sensitive between 8 and 15 weeks of gestation. Women who are exposed to gamma radiation in the pelvic area during this sensitive window may give birth to infants with smaller head or brain size, poorly formed eyes, abnormally slow growth, and mental retardation. There is also the risk of cancer later in life. However, the levels of radiation required to cause these effects is very high, such as from having 500 chest X-rays all at once.

Nuclear power plants

Nuclear power is the generation of electricity from the heat created when uranium atoms are split (uranium is naturally found in the environment). Radioactive waste generated by this process must be stored until it decays to a non-radioactive state, usually taking thousands of years. Disruption of nuclear power facilities can cause leaks of radiation from the plant or from the waste storage areas. This radiation consists of all three types of ionizing radiation (alpha, beta, and gamma) from many radioactive substances including cesium, strontium, and iodine.

What sources of radiation should you be concerned about?

Radon – radon is present in the rock and soil in many areas of the United States. It can seep through the cracks in basements and be inhaled by residents, especially in lower levels of the home. Radon is probably the second highest cause of lung cancer in the US. Basements should be checked for radon using detectors that are readily available in hardware stores.

Medical radiation such as CT scans (MRIs do not release ionizing radiation) – A CT scan exposes you to almost 100 times more radiation than a mammogram. You should receive X-rays and CT scans only when absolutely necessary for diagnosis or treatment of a medical condition.

Nuclear accidents – Leakage from nuclear power plants can occur during accidents. The first protection in a radiation emergency is distance, since radiation level decreases with distance from the source. Populations at risk will be advised to evacuate an affected area. Masks will help prevent the inhalation of alpha particles, and clothing prevents absorption of some beta particles. Iodine tablets protect the thyroid gland from absorbing particles of radioactive iodine, but there are many other substances emitted in a nuclear accident so iodine tablets should not be considered the only type of protection needed.

Helpful information about radiation can be found on the US EPA website at http://www.epa.gov/radiation/docs/402-k-07-006.pdf and http://www.epa.gov/radiation/understand/health_effects.html.

Information on radiation exposure in pregnancy: http://www.bt.cdc.gov/radiation/prenatal.asp.

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