Most people are exposed to radiation every day, but most of it is either harmless non-ionizing radiation or negligibly small doses of ionizing radiation.

Daily exposure to radioactivity is common but occurs in low doses outside of locations near nuclear accidents like Chernobyl and Fukushima. Researchers have detected radiation in tuna, bananas, and the human body due to increasing instrumental sensitivity, not rising concentrations.

Released from underground bedrock before passing through soil, this radioactive gas is produced from the decay of uranium, thorium, and radium and accounts for about half of all human exposure to radiation. It is the leading cause of lung cancer among nonsmokers and can build up in enclosed spaces such as buildings without proper ventilation to dilute the gas.

The damage can increase the risks of cancer, cataracts, heart disease, and other illnesses based on exposure times and intensities. Contaminated food, water, air, or soil from near nuclear accidents can further prolong one's exposure.

Outside the protective atmosphere of Earth, astronauts are constantly bombarded by radiation, which, among other dangers, increases the risk cancer. While those of us on Earth can mitigate the effects of similar radiation by limiting exposure,...

Large doses of ionizing radiation can damage the body within minutes, particularly in the bone marrow and inner layer of the digestive tract. Victims may briefly seem fine before rapidly deteriorating as immune failure, infection and organ collapse set in.

The alpha particle has the strongest ability to ionize other atoms it strikes, but it also does not travel very far before colliding with something and being absorbed. Gamma particles—high-energy photons—do not interact with matter as easily and therefore possess the greatest penetrating power, though this also makes their ionizing potential the smallest.

Ionizing radiation produced by elements such as uranium, polonium, and radium can damage living things, but the trace amounts found in the museum objects that Marie Curie once touched have been largely decontaminated, with more dangerous items stored in protective, lead-lined containers.

Naturally occurring radioactivity comes from radioactive elements underground, cosmic radiation from the sun and other objects in space, and radioactive atoms that make up the molecules we breathe, eat, and drink. Artificial radioactivity is predominantly generated for medical applications and industrial activities.

This calculator from the EPA provides a value in millirems—the US unit for effective dose—based on a variety of exposure parameters, including the state a user lives in and travel-related sources of ionizing radiation, such as passing through screening machines.

Alaska, South Dakota, Pennsylvania, Ohio, and Washington top the list of states with exposure levels above 4 picocuries per liter for this naturally occurring radioactive gas. While these state-level averages vary from one county, municipality, and home to another, the EPA encourages those in the highest-risk states to test their homes.

Since the thyroid gland cannot distinguish between radioactive and non-radioactive iodine, taking potassium iodide pills causes the thyroid to absorb the medication, leaving it unable to take up radioactive iodine from the environment. However, while this protects the sensitive gland against the most prominent radioisotope produced in nuclear accidents, it does not protect other body parts or shield against other radioactive substances.

In the case of radiation-induced distortions in a DNA strand, specialized proteins can cut out entire segments and rebuild them using the second strand as a complementary template. If both DNA strands are completely severed, proteins interlace undamaged DNA with the severed DNA and rebuild both using complementary base pairing.

From space radiation to isolation, humans struggle when it comes to traveling and living in space. What does this mean for long-term spaceflight? This hour-long podcast episode attempts to answer that question while detailing five major spaceflight hazards.

Besides their use for radiometric dating by archaeologists and researchers at museums and universities, radioactive materials are used in sensors that help track ocean currents and analyze pollution, soil, and petroleum products. Radioisotope-based sensors also help measure air in ice cream and prevent spillovers when soda bottles are filled in factories.

Unlike radio waves, microwave, infrared, and visible light, UV light can produce chemical changes, such as curing adhesives and resins, causing substances to fluoresce, and destroying the genetic material of microorganisms. This makes UV light useful for sterilization, forensics, and quickly drying nail polish.

The gases that make up Earth's atmosphere block most harmful forms of electromagnetic radiation from reaching the planet's surface, except for some ultraviolet light. Their transparency to radio waves means this form of light can reach Earth's surface, which is why most radio telescopes are ground-based rather than space-based.

Most of this matter is composed of small particles, with any smaller than 33 feet in diameter burning up in the atmosphere. Larger asteroids can reach the ground, and those larger than several thousand feet cause global damage, including earthquakes and tsunamis.

Spent nuclear fuel remains hot and highly radioactive for long periods, requiring submersion in cooling pools before being stored in dry casks and deep underground repositories. The potential recycling of nuclear waste is impeded by security concerns and dangerous reprocessing methods, particularly when obtaining fresh uranium is often easier.

Although isolation and radiation have driven adaptations in some organisms, decades of radiation have caused ongoing harm to wildlife and vegetation, including population declines in birds and insects. Higher rates of deformities and tumors have also been seen compared with animals in surrounding regions.

Unstable atomic nuclei can transmute into a new element—an atom with a different number of protons—by emitting an alpha particle (two protons and two neutrons) or a beta particle (an electron). The electron can emerge from the nucleus when a neutron, which has no charge, suddenly transforms into a proton and an electron, thereby maintaining zero charge before and after the transformation, but altering the original element.

Because animal tissue is generally more conductive than soil, electricity moving along Earth's surface after a strike tends to travel up and back down an animal's legs, discharging dangerous amounts of energy along the way, with risks increasing the farther apart the legs are. This ground current accounts for about half of all lightning-related deaths and injuries in humans.

The ozone layer blocks almost all of the sun's harmful, including dangerous UVC rays that can damage cells by breaking chemical bonds. Without it, rates of skin cancer, crop failures, oceanic die-offs, and widespread ecosystem collapse would increase significantly, making Earth largely uninhabitable.

Most people breathe in hundreds of Aspergillus fumigatus spores daily without getting sick—it’s a common microscopic fungus in our environment. But people who are severely ill, including those who have undergone an organ transplant, are at risk of developing infections from these spores.

The solar wind engulfs the solar system in a protective bubble called the heliosphere, which was first theorized in the late 1950s based on studies of cosmic rays—high-energy particles traveling through space at near light speed. The heliosphere shields the solar system from much of this ionizing radiation originating elsewhere in the Milky Way.

Ultrafine dust, just 3 micrometers wide, is small enough to bypass lung defenses and enter the bloodstream, where its highly reactive chemicals can cause thyroid disease. Silica in the dust can also cause silicosis, a chronic and incurable lung disease.

Their discoveries of polonium and radium involved ongoing exposure to radioactive materials before shielding technology was developed. Their notebooks, furniture, and other belongings remain radioactive today, requiring researchers to sign a waiver and wear protective clothing to access.

Burning oil depots and bombed buildings are endangering the health of millions of people during the 2026 attacks. Heavy metals from munitions and other damaged materials are going airborne, but the exact health implications depends on dose, wind currents, and other factors including preexisting health conditions.

Through neutron emission, one or more neutrons are ejected from atoms that have far fewer protons. Neutrons can also be released by artificially inducing the fission, or separation, of a large atomic nucleus into smaller ones. During beta-plus decay, a positron—the antimatter version of an electron—is produced when a proton turns into a neutron.

Although they make up no more than 10 out of every million molecules in the ozone layer, ozone provides outsized protection by absorbing the most energetic wavelengths of ultraviolet radiation. This absorption increases thermal energy in the stratosphere, causing temperatures there to rise with altitude.

Tissue in the body can serve as a circuit path between the anode and cathode of a battery, resulting in electrical burns and gradual tissue erosion. Stomach acid can corrode a battery and cause its toxic contents to leak, making a person sick. Batteries for internal use, such as in pacemakers, require special designs.

Its ability to bend around obstacles and reflect off the ionosphere—an electrified layer of Earth's upper atmosphere—allows this type of light to travel long distances without damaging living things due to its low energy. MRI scanners, WiFi, and Bluetooth technologies are also applications of this form of light.