Radon concentrations vary considerably between adjacent buildings, as well as within a building from day to day and from hour to hour. Because of these fluctuations, it is preferable to estimate the annual mean concentration of radon in indoor air by measurements for at least 3 months. Residential radon levels can be measured in an inexpensive and simple manner by means of small passive detectors. Measurements
need to be based on national protocols to ensure consistency as well as reliability for decision-making. Short-term radon tests, done in compliance with national protocols, can be valuable when making decisions during time-sensitive situations, such as home sales or to test the effectiveness of radon mitigation work.
Reducing radon in indoor settings
Well-tested, durable and cost-efficient methods exist for preventing radon in new buildings and reducing radon in existing dwellings. Radon prevention should be considered when new structures are built, particularly in radon-prone areas. In many countries of Europe, and in the United States of America and China, the inclusion of protective measures in new buildings are included in building codes.
Some common ways of reducing radon levels in existing buildings include:
o increasing under-floor ventilation;
o installing a radon sump system in the basement or under a solid floor;
o avoiding the passage of radon from the basement into living spaces;
o sealing floors and walls; and
o improving the ventilation of the building, especially in the context of energy
conservation.
Passive systems of mitigation can reduce indoor radon levels by more than 50%. When radon ventilation fans are added radon, levels can be reduced even further.
Radon in drinking water
In many countries, drinking water is obtained from groundwater sources such as springs, wells and boreholes. These sources of water normally have higher concentrations of radon than surface water from reservoirs, rivers or lakes.
To date, epidemiological studies have not confirmed an association between consumption of drinking-water containing radon and an increased risk of stomach cancer. Radon dissolved in drinking-water is released into indoor air. Normally, a higher radon dose is received from inhaling radon compared with ingestion.
The "WHO guidelines for drinking water quality" [1] (2011) recommend that screening levels for radon in drinking-water be set based on the national reference level for radon in air. In circumstances where high radon concentrations might be expected in drinking-water, it is prudent to measure radon concentrations. Straightforward and effective techniques exist to reduce the concentration of radon in drinking-water supplies by aeration or using granular activated carbon filters. Further guidance is available in “Management of Radioactivity in Drinking-water” [2] (2018).
WHO response
Indoor radon is a preventable risk factor that can be handled through effective national policies and regulations. The "WHO handbook on indoor radon: A public health perspective" [3] provides policy options for reducing health risks from residential radon exposure through:
providing information on levels of radon indoors and the associated health risks;
implementing a national radon programme aimed at reducing both the overall population risk and the individual risk for people living with high radon concentrations;
establishing a national annual average residential radon concentration reference level of 100 Bq/m3, but if this level cannot be reached under the prevailing country-specific conditions, the reference level should not exceed 300 Bq/m3;
developing radon measurement protocols to help ensure quality and consistency in radon testing;
implementing radon prevention in building codes to reduce radon levels in buildings under construction, and radon programmes to ensure that the levels are below national reference levels;
promoting education for building professionals and providing financial support to remove radon from existing buildings; and
considering the inclusion of radon as a risk factor in national strategies related to cancer control, tobacco control, indoor air quality and energy conservation.
These recommendations are consistent with the International Basic Safety Standards [4] (2014), co-sponsored by WHO and other international organizations. WHO promotes the implementation of these radon standards, which ultimately support the 2030 Agenda for Sustainable Development Goals (SDG), and Target 3.4 on noncommunicable diseases. To help monitor national radon policies and regulations around the world, WHO has assembled a radon database [5] as part of the WHO Global Health Observatory.
Footnotes
1 Radioactivity is measured in units called Becquerels (Bq). One Becquerel corresponds to the transformation (disintegration) of one atomic nucleus per second. Radon concentration in air is measured by the number of transformations per second in a cubic meter of air (Bq/m3).
References
[1] Guidelines for drinking-water quality, 4th edition, Geneva, WHO (2011)
[2] Management of Radioactivity in Drinking-water, Geneva, WHO (2018)
[3] WHO Handbook on Indoor Radon: A Public Health Perspective, Geneva, WHO (2009)
[4] Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, Vienna, IAEA (2014)
[5] WHO Global Health Observatory: Radon database on national policies and regulations
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