Radon

Radon
Name	Radon
Atomic number	86
Appearance	colorless gas
Category	noble gas
Phase	gas
Discovered	1899
Discoverer	Friedrich Ernst Dorn
Mass number	222

Radon is a naturally occurring, radioactive noble gas produced by the decay of heavier elements in the uranium decay series and thorium decay series. It exists as isotopes such as an unstable form derived from uranium-238 and is significant in fields ranging from geology to public health. Studies of its behavior inform research in mining safety, building construction, and radiation protection.

Overview

Radon arises primarily through alpha decay of radium-226 in the uranium-238 chain and has historically been studied by figures like Ernest Rutherford and Marie Curie; the element's identification followed investigations at institutions such as the University of Leipzig and the Kaiser Wilhelm Institute. Its presence has shaped responses by agencies including the World Health Organization and the Environmental Protection Agency to indoor air quality concerns. Research programs at universities like Harvard University and University of Oxford examine radon transport in soils and implications for epidemiology studies coordinated with organizations such as the International Agency for Research on Cancer.

Properties

Radon is a chemically inert, colorless, odorless noble gas with high atomic mass and radioactivity. Its most stable isotope, produced from radium-226, has a half-life relevant to environmental persistence studied by laboratories at institutions like the National Institute of Standards and Technology and the Oak Ridge National Laboratory. The element’s physical properties have been measured alongside other noble gases such as xenon and krypton in comparative work by researchers affiliated with the Royal Society and the Max Planck Society. Radon’s radiological behavior underpins protocols developed by the International Commission on Radiological Protection and informs detector calibration standards used by agencies including the European Commission.

Occurrence and distribution

Radon is emitted from soils, rocks, and groundwater in regions with elevated concentrations of uranium and thorium, such as parts of Pennsylvania, Cornwall, and the Urals. Geological formations like granite, shale, and phosphate deposits are notable sources noted in surveys by the United States Geological Survey and the British Geological Survey. Indoor concentrations vary with building practices in countries like Canada, Japan, and Finland, prompting national measurement campaigns led by entities such as the Health Canada and the Finnish Radiation and Nuclear Safety Authority. Radon transport is affected by faults and fractures studied in projects sponsored by the European Geosciences Union and incorporated into hazard mapping by regional authorities like the Alberta Geological Survey.

Health effects and risks

Long-term inhalation of radon decay products increases the risk of lung cancer, a conclusion supported by cohorts such as miners monitored in studies by the National Cancer Institute and case-control studies coordinated with the International Agency for Research on Cancer. Occupational exposures in historic sites like the Jáchymov mines were influential in establishing dose-response relationships used by World Health Organization reports and recommendations from the International Commission on Radiological Protection. Public health guidance from agencies such as the Centers for Disease Control and Prevention and national ministries of health addresses risk communication, while epidemiological analyses incorporate data from registries like the Surveillance, Epidemiology, and End Results Program.

Detection and measurement

Measurement techniques include passive devices such as charcoal canisters and alpha-track detectors developed and validated by standards organizations like the American Society for Testing and Materials and the International Organization for Standardization, as well as active devices such as continuous radon monitors used in research at facilities like the Atomic Energy of Canada Limited. Calibration and proficiency testing occur through laboratories affiliated with the National Physical Laboratory (United Kingdom) and the Laboratoire national de métrologie et d'essais. Large-scale surveys employ protocols from agencies like the Environmental Protection Agency and the European Commission’s Joint Research Centre.

Mitigation and prevention

Mitigation methods include sub-slab depressurization, increased ventilation, and sealing of entry routes, techniques developed and refined by engineering groups at institutions such as the Lawrence Berkeley National Laboratory and the National Research Council (Canada). Building codes in regions including Newfoundland and Labrador and Scotland integrate radon-resistant construction guidance from authorities like the World Health Organization and standards bodies like the International Code Council. Remediation firms often follow protocols recommended by national agencies such as the Environmental Protection Agency and the Health Protection Agency.

Regulation and guidelines

Regulatory limits and action levels vary by jurisdiction: the Environmental Protection Agency recommends action at 4 pCi/L in the United States, while the World Health Organization suggests a lower reference level; European Union directives set requirements for member states and are implemented by agencies like the Health and Safety Executive in the United Kingdom. National regulations are enforced through ministries and agencies including the Ministry of Health (Japan), the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (Germany), and provincial authorities such as the Ontario Ministry of the Environment, Conservation and Parks.

Category:Chemical elements Category:Radioactive elements