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The risks of radiation exposure grabbed the public health spotlight following the devastating earthquake and tsunami in Japan on March 11, 2011. Damage at the Daiichi nuclear power plant in Fukushima prompted concern that Daiichi employees, rescue workers, and people living near the plant might be exposed to dangerous levels of radiation and that Japan’s food and water sources would be contaminated. This concern, however, was not confined to Japan, as the international community, including the United States, began to fear that people elsewhere might also be exposed to harmful levels of radiation.

Though the health concerns surrounding Japan’s nuclear disaster are certainly legitimate—according to the Environmental Protection (EPA), “It’s natural to be concerned about pollution in the environment, especially in the wake of an accident such as that at Fukushima”—radiation exposure in our daily lives is nothing new. We are exposed through environmental sources (including radioactive material in soil, water, and air), and, ironically, we may also be exposed when we take measures to protect or improve our health; some diagnostic and screening tests, like X-rays and computed tomography (CT) scans, use radiation to detect illness or injury, and radiation is also used in cancer treatment.

With so much radiation around us, how do we know which levels should be of concern? And how do we protect ourselves from dangerous exposures? To answer these questions, we look at some basic information about radiation and some of its common sources.

Radiation Basics

Radiation Defined

The Centers for Disease Control and Prevention defines radiation on its website as “energy that travels through space and may be able to penetrate various materials.”

There are three sources of radiation exposure: naturally occurring sources, medical radiation, and radiation from nuclear power plants. Levels, or doses, of radiation from these sources are measured with a unit called a sievert (Sv). According to the World Health Organization, a person’s average radiation exposure amounts to 3.0 millsieverts (mSv) per year, though levels vary in certain parts of the world. Natural radiation accounts for 80 percent (2.4 mSv) of annual exposure, medical use for 19.6 percent (almost 0.6 mSv), and nuclear plants for 0.4 percent (about 0.01 mSv).

Health Risks

Radiation exposure can produce both immediate (acute) effects and long-term effects.

Acute effects—which are a concern following a nuclear power plant accident and are more likely to affect rescuers, first responders, and plant workers—include skin redness, hair loss, radiation burns, and acute radiation syndrome, a severe illness that often begins with nausea and vomiting and can progress to more serious problems. The general public is at less risk of acute effects because it’s unlikely that anyone outside of the plant would be exposed to high enough levels of radiation.

Over the long term, exposure to radiation can increase the risk of cancer, particularly thyroid cancer. This risk stems from the fact that when radioactive iodine is released during a nuclear emergency, it may be inhaled or swallowed and then concentrates in the thyroid. Children and young adults have a higher risk of thyroid cancer as a result of radiation exposure.

Fetuses are also at risk when exposed to radiation. According to the World Health Organization, a fetus may be at risk of brain cancer when exposed to radiation between eight and 15 weeks of gestation, and children exposed to radiation before birth may have an increased risk of childhood cancers.

Types of Radiation

Natural Radiation

Though we might be alarmed by the thought of radiation exposure, we’re actually exposed to radiation every day. This daily exposure comes from natural radiation (also called background radiation), which comes from space (cosmic rays) and is emitted from radioactive materials that occur naturally in soil, water, and air.

For example, many people are familiar with radon, a cancer-causing radioactive gas. High concentrations of radon in the soil beneath a house can put occupants at risk. As a result, many people have their homes tested for radon (see sidebar “Managing Your Radiation Exposure”).

Radiation for Medical Use

The use of radiation in the medical setting has improved treatment for some diseases (such as many types of cancer) as well diagnosis of disease and injury with tests such as X-rays and CT scans. The benefits of medical radiation, however, are accompanied by certain risks. Radiation is a known carcinogen—a substance that can cause cancer—and as a result large amounts of radiation exposure, even for a potentially beneficial purpose like disease screening, can raise an individual’s risk of cancer.

The risk of cancer associated with exposure to medical radiation increases with cumulative exposure and with excessive doses. Infants, children, and young adults may be especially vulnerable due to their small body size, though grown adults can also receive excessive doses. As well, people who are exposed to medical radiation many times (high cumulative dose) may have an elevated risk of cancer. Common sources of medical exposure include radiation for cancer treatment, mammograms, CT scans, and all types of X-rays.

According to Richard Morin, PhD, a medical physicist at the Mayo Clinic in Jacksonville, Florida, a chest X-ray is the most common medical source of radiation exposure. He explains  that CT scans are gaining attention when it comes to radiation exposure because these tests are being used with increasing frequency. Dr. Morin says that a CT scan uses more radiation than a chest X-ray but that the real concern remains the frequency of their use.

The encouraging news about medical radiation is that there are steps you can take to manage your risk. It’s also important to remember that medical procedures can have important health benefits, such as early, accurate diagnosis. With this in mind, Dr. Morin says that the key is to “optimize” exposure by carefully selecting tests based on their potential benefit. “So long as the test is appropriately ordered, the benefit far outweighs the risk,” he says.

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Radiation from a Nuclear Power Plant Accident

As a result of Japan’s recent nuclear accident, awareness of the risks concerning nuclear power plant radiation has grown. In a nuclear power plant accident, individuals within the plant and nearby may be exposed to products generated inside the reactor, or nuclear fission products. Specifically, radioactive caesium and radioactive iodine are the products (also called radionuclides) that can cause both immediate and long-term health issues. These radio These radio-nuclides are released into the air and may be inhaled and can contaminate food and water sources.

People exposed to significant amounts of radiation (such as in a nuclear accident) can minimize further exposure by taking off clothing and shoes worn at the time of exposure and washing skin and hair with soap and water. Drugs can also be used to help reduce health effects; these include drugs to increase white blood cell production to reduce damage to the bone marrow and the risk of infections as well as drugs to help protect internal organs by accelerating the removal of radioactive material from the body.

It’s clear that even without a nuclear accident, radiation is a part of our daily lives, whether we knowingly expose ourselves in the medical setting or are surrounded by unavoidable environmental sources. It’s encouraging to know that measures are in place to protect us from dangerous levels of exposure; government agencies like the EPA continuously monitor radiation levels throughout the United States, and awareness of the risks of medical radiation can help us make safer healthcare choices.

Managing Your Radiation Exposure

Here are a few proactive steps that you can take to manage your exposure:

  • Keep a record of all of your radiation exposure (such as all scans that use radiation and radiation for cancer treatment).
  • If you’re exposed to radiation on the job (as are airport security workers, for example), take this into account.
  • Discuss with your doctor diagnostic nonradiation alternatives to scans that use radiation; magnetic resonance imaging (MRI) and ultrasound, for example, don’t use radiation. When considering alternatives, Dr. Morin says to make sure that you and your physician are choosing the most appropriate exam. He also says you can ensure that you’re receiving safe and effective treatment by making certain the facility you choose is accredited by the American College of Radiology.
  • Test your home for radon. You can do this yourself, with kits available at most hardware stores, or you can hire a qualified radon tester. For more information visit
  • If the radon level is 4 picocuries per liter (pCi/L) or higher, the EPA recommends taking steps—like installing a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside to lower the level in the home. For more information about testing for radon levels and reducing exposure, visit

Radiation from Japan: Was the United States at Risk?

The damage to the Daiichi nuclear power plant following the March 2011 tsunami and earthquake in Japan raised concerns about radiation exposure in Japan and beyond.  Many Americans soon wondered whether radiation from Japan would reach US soil in high enough concentrations to be a health threat.

So, were we at risk in the United States? It’s not likely. The World Health Organization reports that radiation levels measured in countries other than Japan, including the United States, are too low to increase radiation-related health risks. In fact, current levels related to the Japan incident are much lower than the average level of background radiation that we’re exposed to regularly.

It’s also reassuring to know that the EPA is monitoring radiation levels across the United States, using its nationwide radiation monitoring system, RadNet, to check radiation levels in the air as well as in drinking water, milk, and precipitation. According to the EPA, results have been “far below levels of public-health concern.” The EPA also recognizes the importance of communicating RadNet findings to the public to relieve unnecessary worry. A spokesperson for the EPA says the organization devotes a great deal of effort to making public all of the data collected and takes measures to have RadNet findings posted on the EPA website as quickly as possible.

Another concern has been that food grown or processed in Japan may be contaminated with radioactive material from the Daiichi accident. Though it is possible for food to become radioactive (through the air, rain, snow, soil, and water sources), Japanese authorities have put measures in place to set regulatory limits on radiation and to monitor radioactivity in food. Many other countries are also monitoring food from Japan (such as the US Food and Drug Administration currently does) or are not currently importing food from Japan.

A Look Back: The Chernobyl Accident

This past spring marked 25 years since the devastating nuclear power station accident in Chernobyl, then part of the former Soviet Union (now Ukraine). On April 26, 1986, a meltdown of reactor four resulted in an explosion and a fire that released significant amounts of radioactive material into the environment.

The most severe effects of the radioactive fallout were in areas closest to the Chernobyl plant and the neighboring regions. Increased levels of radioactivity were also measured in the United States, but, like the more recent nuclear incident in Japan, these levels were not high enough to be a significant public health concern.

The highest levels of exposure from the Chernobyl accident were received by recovery operation workers and people who had to be evacuated from the site. People living in and around contaminated areas were also affected. Health effects seen in the Chernobyl population included acute radiation sickness (fatal in some cases) among a portion of workers on-site at the time of the meltdown and radiation-induced cataracts among many who survived radiation sickness. Cancers were also associated with the incident, with thyroid cancer being the most common (particularly among people exposed as children or adolescents) as well as an increased incidence of leukemia.

The tragedy of Chernobyl does have a positive legacy in the improvements to nuclear safety and response to nuclear emergencies. As result of the Chernobyl incident, we are better prepared on a global scale to respond to a nuclear disaster and manage its consequences due to enhanced cooperation among different countries. In addition, researchers continue to learn more about the health effects of radiation exposure through ongoing studies among people affected by the Chernobyl accident. Though the ultimate goal is of course to avoid future nuclear accidents, it’s important to acknowledge the significant strides made in nuclear safety and emergency response in the past 25 years.

Radiation Resources

Environmental Protection Agency

World Health Organization

Centers for Disease Control and Prevention

US Nuclear Regulatory Commission

American College of Radiology

US Food and Drug Administration