A radionuclide is an atom with an unstable nucleus due to an excess of neutrons or protons, which results in radioactive decay and the emission of radiation in order to achieve a more stable state. Also referred to as radioactive isotopes or radioisotopes, radionuclides occur both naturally and are produced artificially in nuclear reactors and particle accelerators for medical, industrial and research purposes. Their production is a major secondary application of nuclear reactors.
Radionuclides can enter the atmosphere through natural processes and from accidental releases from nuclear facilities and from mining and other industrial activities and become another component of air pollution. While in the air, they can attach to aerosols and particles, which can then be inhaled or deposited on surfaces, where they can contaminate water bodies and the soil and eventually the groundwater.
Although radionuclides are not directly produced by road traffic, such traffic can contribute to the resuspension of radionuclides that are already present in the environment into the air. This resuspension occurs through abrasion by tires on road surfaces and through induced turbulence created by the moving vehicles.
While the direct effect on human health from radionuclides in the environment is typically less than from other sources such as radon in homes and medical exposure, the long-term exposure to radionuclide-contaminated environments, particularly through the consumption of contaminated water and food, can still be dangerous to both humans and other species, including increased risks of genetic damage and cancer.