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Uranium

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Uranium

Uranium is a naturally occurring heavy metal that has a relative abundance within the earth’s crust similar to that of silver or gold. Uranium can be found in the environment as different isotopes, with Uranium-238 being the most commonly occurring (99% frequency).

Isotope: An element with a different number of neutrons within it’s atomic structure making it characteristically heavier or lighter as a result. For example, Carbon is known to commonly have 6 neutrons, but can also be found as an isotope with 7 neutrons.

Uranium is naturally found in geologic environments but can become mobilized due to human practices like mining. Consequently, Uranium can be transferred into surface water or groundwater systems due to leaching and can also be more commonly occurring in soil sediments near mine sites. Furthermore, Uranium can be transferred to water systems (e.g. lakes, streams) through agricultural practices since some fertilizers contain uranium concentrations within them. Ingestion of uranium commonly occurs due to drinking water or food, in which the world health organization's drinking water standard is set at a threshold of 2 micrograms/Litre. Nuclear facilities and military operations are also sources of Uranium in the environment due to storage leaks and use for Uranium as fuel, respectively.

Regarding health concerns associated with Uranium, individuals can undergo chemotoxicity and radiotoxicity. Chemotoxicity refers to health issues associated with uranium as a heavy metal, and not as a radioactive material, and its associated impacts on individual’s cells, genetics, and tissue. Chemotoxicity health impacts are typically associated with naturally occurring uranium in the environment, since naturally occurring uranium does not have elevated radiation levels. Some associated health impacts include organ tissue scarring/ necrosis, hormone imbalances, impedance in bone functionality, and inflammation.

Radiotoxicity is of concern for high uranium mass concentrations (enriched uranium) that can be found in nuclear power plants. Uranium naturally decays and continuously ejects high energy elemental and radioactive byproducts that can be harmful if they come in contact with tissue. These byproducts increase the likelihood of radiotoxicity, such as radium which releases more radiation per atom than Uranium, or radon which is extremely toxic and cancer-causing. Some associated radiotoxicity symptoms of uranium include lung cancer, bone cancer, leukemia, genetic damage, and birth defects.

Radon

Radon is a naturally occurring gas that originates from the decay of uranium metal. The gas can be present in soils, groundwater, surface water, or the air and concentrations are dependent on the amount of uranium present in the environment. Radon concentrations within the air are typically higher over large land mass areas and can be affected seasonally by wind speeds, humidity, and temperature. Some rock types contain higher concentrations of radon, such as shale or phosphate ores from mining operations. In fact, dependent on the type of rock and its origin, some building materials for households can contain radon, such as bricks, concrete, or tile; although these radon contributions are minimal. Generally, stirring up soils or geologic deposits have the potential to release increased radon concentrations into the environment, especially in uranium rich soils.

Radon has a very short half life of 3.8 days and releases short lived radioactive byproducts as a result. These byproducts contain alpha particles which are harmful to individuals and can cause associated cancers or genetic damage. Alpha particles are a small set of high energy atoms (2 protons, 2 neutrons) that have the potential to damage the genetic DNA of cells by knocking out or breaking off portions of DNA structures, which in turn can cause cells to operate incorrectly and cause various cancers. Radon byproducts are electrically charged and can attach to aerosols or dust and be inhaled, allowing these constituents to emit alpha particles from within the lungs. Consequently, lung cancer is a common health effect from radon exposure, in which there have also been cases of leukemia and lymphoma.

Half life: The amount of time required for a substance to be degraded down to half of its original mass.

Tritium

Tritium is an isotope of hydrogen, meaning that it has a similar atomic structure to hydrogen but has a different number of neutrons. The majority of hydrogen atoms are made up of 1 proton and 0 neutrons, however, isotopes of hydrogen can have 1 neutron (deuterium) or 2 neutrons (tritium). Tritium is naturally formed in the atmosphere from high energy neutrons and protons within cosmic rays (particles from outer space) that react with oxygen and nitrogen in the earth’s atmosphere. Once tritium is formed it can bind to water molecules in the air and form titrated water, which occurs when tritium replaces the hydrogen atom in a water molecule. Titrated water can then enter water systems (e.g. lakes, streams) and enter drinking water, introducing a potential exposure pathway to the population. Tritium can additionally bind with organic matter (carbon containing molecules) and become bonded within trees, plants or animal tissue. In addition to natural tritium sources there are also man-made sources, which are responsible for the majority of tritium found in the environment. Man-made sources include past nuclear weapons testing, decommissioning of reactors from nuclear power plants, use in hospitals, and use in industrial processes due to tritium’s luminescent properties (glow in the dark watch faces, compasses, signs).

In fact, due to nuclear testing in the 1960s, tritium concentrations within rainwater were 1000 times higher due to radioactive fallout.

Tritium is radioactive (Half life of 12.31 years) and continuously decays over time and emits low energy radiation called beta rays. It is generally accepted that naturally occurring tritium in the environment does not have a high enough radiation dose to cause negative health effects. In a calculation conducted by the Government of Canada on tritium exposure, it was determined that if an adult were to ingest tritium contaminated water on a daily basis, an expected radiation exposure of 0.00027 mSv would be expected. This exposure dose is very low, in which exposure values above 100 mSv are expected to cause cancers. However, extremely high quantities of tritium can cause harmful health effects related to cancer, developmental issues, and genetic damage in both humans and animals. Tritium within nuclear facilities are typically used in large quantities, but its release into the environment is controlled. It is important to note that accidental leakage of tritium into the environment from nuclear power plants can still cause associated health effects to the nearby population.