Most people are unaware that many fruits, nuts and vegetables are radioactive. There is radiation everywhere, even in our own bodies. A new study on the radiation emitted by everyday objects highlights the fact that we interact with radioactive materials every day.
A variety of dangerous radioactive materials are known to be released during nuclear power plant accidents and there are simple strategies to detox from different types of radiaiton. Among the most worrisome are cesium-137 and iodine-131, which emit Gamma rays and have affinities for parts of the human body. Cesium-137 mimics potassium inside the body and accumulates mainly in the liver, kidneys, and the reproductive system. Iodine-131 is rapidly absorbed by the thyroid gland and increases the risk of thyroid growths and cancer.
But not all radioactive materials are dangerous. The goal of the study is to give people a frame of reference for understanding news stories or other information about radiation and nuclear safety.
Bananas, carrots, potatoes, avocados, nuts, beans and red meat all contain modest amounts of radioactive elements. Even granite countertops could be considered health hazards if we take measurements too seriously.
Bananas are just one of many foods that we eat on a daily basis which, thanks to ingredients like potassium and radium, produce naturally-occurring and measurable amounts of radiation. In fact, that banana is so good at producing a constant, easily measurable amount of radiation that it's used as a convenient yardstick for measuring radioactivity.
"We did this study because understanding how much radiation comes off of common household items helps place radiation readings in context -- it puts things in perspective," says Robert Hayes, an associate professor of nuclear engineering at North Carolina State University. "If people understand what trace levels of radiation mean, that understanding may help prevent panic."
The researchers used a portable gamma radiation meter to measure the external gamma radiation emitted in a North Carolina home. The radiation was measured in microgray per hour (microGy/hr).
Avocados, for example, gave off 0.16 microGy/hr of gamma radiation -- slightly less than the 0.17 microGy/hr emitted by a banana. Bricks gave off 0.15 microGy/hr, while smoke detectors (with their americium components) gave off 0.16. By way of comparison, natural uranium ore measured 1.57 microGy/hr.
If there was an award for "Most Radioactive Food," it would go to Brazil nuts. Brazil nuts contain high levels of two radioactive elements: radium and potassium. Potassium is good for you, used in many biochemical reactions, and one of the reasons why the human body is itself slightly radioactive. Radium occurs in the ground where the trees grow and is absorbed by the plant's root system.
"If you're surprised that your fruit is emitting gamma radiation, don't panic," Hayes says. "The regulatory level for workers -- which is safe -- is exposure to 50,000 microGy per year. The levels we're talking about in your household are incredibly low."
The paper, "Contributions of Various Radiological Sources to Background in a Suburban Environment," is published in the journal Health Physics. Lead author of the study is Richard Milvenan, a former master's student at NC State.