You are exposed to radioactivity every day, often from the foods you eat and the products you use. Here is a look at some common everyday materials that are radioactive. Some of these objects may pose a health risk, but most of them are a harmless part of your everyday environment. In almost all cases, you get more exposure to radiation if you take a ride in a plane or get a dental x-ray. Still, it's good to know the sources of your exposure.

Brazil Nuts Are Radioactive Jennifer Levy/Getty Images Brazil nuts are probably the most radioactive food you can eat. They provide 5,600 pCi/kg (picocuries per kilogram) of potassium-40 and a whopping 1,000-7,000 pCi/kg of radium-226. Although the radium is not retained by the body for very long, the nuts are approximately 1,000 times more radioactive than other foods. It's interesting to note the radioactivity seems not to come from elevated amounts of radionuclides in the soil, but rather from the extensive root systems of the trees.

Beer Is Radioactive Jack Andersen/Getty Images Beer is not particularly radioactive, but a single beer does contain, on average, about 390 pCi/kg of the isotope potassium-40. All foods which contain potassium have some of this isotope, so you could sort of consider this a nutrient in beer. Of the items on this list, beer probably is the least radioactive, but it's amusing to note that it is, in fact, slightly hot. So, if you were afraid of the Chernobyl energy drink from that movie "Hot Tub Time Machine," you might want reconsider. It could be good stuff.

Kitty Litter Is Radioactive Kitty litter that is made from clay or bentonite is slightly radioactive. GK Hart/Vikki Hart, Getty Images Cat litter is sufficiently radioactive that it can set off radiation alerts at international border checkpoints. Actually, it's not all cat litter you need to worry about — only the stuff made from clay or bentonite. Radioactive isotopes naturally occur in clay at the rate of about 4 pCi/g for uranium isotopes, 3 pCi/g for thorium isotopes, and 8 pCi/g of potassium-40. A researcher at Oak Ridge Associate Universities once calculated American consumers buy 50,000 pounds of uranium and 120,000 pounds of thorium in the form of cat litter each and every year. This does not pose much of a danger to cats or their humans. However, there has been a significant release of radionuclides in the form of pet waste from cats being treated for cancer with radioisotopes. Gives you something to think about, right?

Bananas Are Naturally Radioactive Banar Fil Ardhi/EyeEm/Getty Images Bananas are naturally high in potassium. Potassium is a mix of isotopes, including the radioactive isotope potassium-40, so bananas are slightly radioactive. The average banana emits around 14 decays per second and contains about 450 mg of potassium. It's not something you need to worry about unless you are hauling a bunch of bananas across an international border. Like kitty litter, bananas can trigger a radiation alert for authorities seeking nuclear material. Don't think bananas and Brazil nuts are the only radioactive foods out there. Basically, any food that is high in potassium naturally contains potassium-40 and is slightly, but significantly radioactive. This includes potatoes (radioactive french fries), carrots, lima beans and red meat. Carrots, potatoes, and lima beans also contain some radon-226. When you get right down to it, all food contains a small amount of radioactivity. You eat food, so you are slightly radioactive, too.

Radioactive Smoke Detectors Many smoke detectors contain a small sealed americium-241 radioactive source. Whitepaw, public domain About 80% of standard smoke detectors contain a small amount of the radioactive isotope americium-241, which emits alpha particle and beta radiation. Americium-242 has a half-life of 432 years, so it's not going anywhere anytime soon. The isotope is enclosed in the smoke detector and poses no real risk to you unless you break apart your smoke detector and eat or inhale the radioactive source. A more significant concern is the disposal of smoke detectors since the americium eventually accumulates in landfills or wherever discarded smoke detectors wind up.

Fluorescent Lights Emit Radiation Ivan Rakov/EyeEm/Getty Images The lamp starters of some fluorescent lights contain a small cylindrical glass bulb containing less than 15 nanocuries of krypton-85, a beta and gamma emitter with a half-life of 10.4 years. The radioactive isotope is not a concern unless the bulb is broken. Even then, the toxicity of other chemicals typically outweighs any risk from radioactivity.

Irradiated Gemstones Mina De La O/Getty Images Some gemstones, such as zircon, are naturally radioactive. Additionally, several gemstones may be irradiated with neutrons to enhance their color. Examples of gems that may be color-enhanced include beryl, tourmaline, and topaz. Some artificial diamonds are made from metal oxides. An example is yttrium oxide stabilized with radioactive thorium oxide. While most of the items on this list are of little to no concern where your exposure is concerned, some radiation-treated gemstones retain enough "shine" to be radiologically hot to the tune of 0.2 milliroentgens per hour. Plus, you may wear the gems close to your skin for an extended period of time.

Radioactive Ceramics Steffen Leiprecht/STOCK4B/Getty Images You use ceramics every day. Even if you aren't using old radioactive stoneware (like brightly-colored Fiesta Ware), there's a good chance you have some ceramics that emit radioactivity. For example, do you have a cap or veneer on your teeth? Some porcelain teeth have been artificially colored with uranium containing metal oxides make them whiter and more reflective. The dental work can expose your mouth to 1000 millirem per year per cap, which comes out to two and a half times the average whole body annual exposure from natural sources, plus a few medical x-rays. Anything made of stone may be radioactive. For example, tiles and granite countertops are slightly radioactive. So is concrete. Concrete basements are especially high since you get off-gassing of radon from the concrete and collection of the radioactive gas, which is heavier than air and can accumulate. Other offenders include art glass, cloisonne enameled jewelry, and glazed pottery. Pottery and jewelry are of concern because acidic foods can dissolve small amounts of radioactive elements so that you might ingest them. Wearing radioactive jewelry close to your skin is similar, where the acids in your skin dissolve the material, which may be absorbed or accidentally ingested.

Recycled Metals That Emit Radiation Metal cheese graters, like many items, may be made from recycled metal. Frank C. Müller, Creative Commons License We all want to reduce our impact on the environment. Recycling is good, right? Of course, it is, as long as you know what it is you're recycling. Scrap metal can get grouped together, which has led to some interesting (some would say horrifying) cases of radioactive metal getting incorporated into common household objects. For example, back in 2008, a gamma-emitting cheese grater was found. Apparently, scrap cobalt-60 found its way into the metal used to make the grates. Metal tables contaminated with cobalt-60 were found scattered across several states.