We are constantly exposed to some level of radiation on a normal basis. It is a natural part of our planet. That natural radiation becomes ionized by the ground, outer space, and even human bodies. Therefore, we breathe it in the air, eat it in our foods and drink it in our water. Even our homes contain these low levels of radiation due to the building materials.Certain foods, building materials and locations have higher levels of natural radiation. Items, like tobacco, fertilizer or welding rods, can also add to our exposure. In most cases, this exposure is nothing of concern. Exceptions include natural gas exposure like radon that may contaminate the air we breathe.
In the U.S., the average annual exposure to radiation measures 6.2 millisieverts (mSv). About half of the exposure stems from natural radiation with the other half due to medical procedures. A cancer screening CT scan, for example, produces about 10 mSv. Both natural and man-made sources affect us in the same way with no detectable health risks at these low levels.
The Nuclear Regulatory Commission (NRC) acknowledges a dose-response relationship between radiation and cancer stating that any amount of exposure can create a risk for cancer with the risk increasing as exposure increases. The NRC has set regulations on the amount radiation exposure within the Code of Federal Regulations. They have even set a limit for those who work with radioactive material at 50 mSv. To put the Fukushima accident in perspective, it is likely that the Japanese volunteers in the Fukushima nuclear plant incident have been exposed to 250 – 500 mSv.
Effects of Radiation Exposure
Different people are more or less affected by radiation depending on their level of health before exposure. Therefore, there is no one safe level of radiation.
Low levels of radiation exposure may be so small that they are undetectable. The repair mechanisms of our bodies help to protect against small amounts of radiation. Unlike acute radiation that tends to kill cells, low doses are more likely to damage or even alter cell DNA. Genetic effects resulting from mutated reproductive cells, like congenital abnormalities or still births, are 5 times less likely to occur than cancer. Leukemia and cancer have been known to be the adverse health effects of radiation exposure. About 1 out of 100 people die of cancer due to normal levels of radiation. However, if there is a long latent period, radiation causing cancer that’s not detected until years later may not be linked to the exposure but to some other carcinogen. Currently, there is no data to directly connect cancer to radiation exposure of less than 100 mSv.
High levels of ionizing radiation begin at around 500 mSv. Symptoms may appear within days or even hours of exposure, including nausea, diarrhea or vomiting. Greater exposure will bring on symptoms faster and have a higher probability of death. Acute Radiation Syndrome is detected by a rapid bodily response to the high dose. Scientists believe that if a population were exposed to 3,500 – 5,000 mSv, half would die within the timeframe of a few minutes to 30 days. In the instance of Chernobyl, for example, workers were exposed to doses of 800 – 16,000 mSv. Many died within months of the exposure.
Protection from Radioactive Exposure
There is a false belief that salt products, or increased sodium, will help to protect against nuclear radiation. However, one would need to consume an excessive amount of salt to get enough iodide to have any benefit. Instead of salt infused products, potassium iodide is also available in tablet form. The non-radioactive iodine is intended to saturate the thyroid gland so that any later exposure to radioactive iodine would only be excreted and not absorbed by the thyroid. If the thyroid glad is exposed to radiation, this could lead to thyroid cancer as discovered from Chernobyl. Exposure will come less from the air and more from sources like food and milk. People are cautioned, however, against taking iodide tablets as a mere preventative measure with no real danger identified. The iodide can cause significant side affects to certain individuals including those allergic to iodide, with shellfish allergies, or having compromised thyroids.
Environmental Radiation Tracking
To ease people’s fears, the U.S. Environmental Protection Agency (EPA) monitors radiation releases throughout the United States using a system called RadNet. This network of stations tracks and documents the trends in environmental radiation. Air, drinking water, milk and precipitation are all collected samples to assess radioactive levels. Data is collected and published to assess public exposure and environmental impacts.
