MAP OF SUSCEPTIBILITY TO RADON -- Parishes with more than 10% high-risk area are considered highly susceptible (Elevado) (1,812 parishes); parishes with more than 10% moderate-risk area and less than 10% high-risk area are considered moderately susceptible (Moderada) (750 parishes), and parishes with less than 10% high-risk and moderate-risk areas are considered to have low susceptibility (Baixa) (320 parishes).
Radon is the second leading cause of lung cancer after cigarette smoking in Portugal. Although the country has studied the radioactive gas since the 1980s, the proposed National Plan for Radon is the first to set out requirements for all affected sectors, such as construction, health and education, to reduce the risks of prolonged exposure to the radioactive gas in homes, public buildings and workplaces such as mines.
It is estimated that radon causes between 3 percent and 14 percent of all lung cancers in a country, depending on the national average radon level and the smoking prevalence, according to the World Health Organization (WHO). Smokers are estimated to be 25 times more at risk from radon than non-smokers.
Aside from smoking, the U.S. Centers for Disease and Control and Prevention adds that burning wood, coal or other substances that add particles to the indoor air also increases the chances of contracting lung cancer.
The public has until April 1 to participate with comments and opinions on the integrated National Plan for Radon. On a list of radon susceptibility, each parish is grouped under its municipality and described as baixo (low), moderado (moderate) and elevado (high).
Radon has no smell or color. The gas forms naturally when uranium, thorium or radium, which are radioactive metals, break down in rocks, soil and groundwater. People can be exposed to radon, primarily, from breathing it in air that comes through cracks and gaps in buildings and homes. The radioactive particles are retained in human airways and emit radiation, causing damage to the lungs, according to the National Plan for Radon. The longer the exposure to radon, the greater the risk of developing lung cancer. It may take years before the appearance of health problems, according to the U.S. Centers for Disease Control and Prevention.
In some areas, such as the granite landscapes that are found in Central and Northern Portugal, radon levels are higher than elsewhere. Besides the geological characteristics, the type of construction and the use of the building are also variables, according to the National Plan for Radon.
With a view to ensuring protection from the risks of exposure to radon and reducing its effects on health, the National Plan for Radon (PNR) provides for the following actions:
1. Defining methodological guidelines for the measurement, remediation and prevention of radon;
2. Promoting research and development in the field of radon;
3. Defining obligations and commitments in managing radon exposure in the workplace;
4. Promoting the quality of services and professional qualification; and
5. Disseminating reliable information and defining communication strategies with the public.
The National Plan for Radon is based on three pillars of action:
1. Characterizing exposure situations for workers and the general public, analyzing the national territory and defining appropriate methodologies and protocols supported by science;
2. Reducing the risk of exposure to radon, identifying actions leading to more efficient and sustainable mitigation systems, combined with the provision of quality services;
3. Designing guidelines for efficient communication strategies and creating dissemination mechanisms adapted to various target audiences and the general public.
According to the World Health Organization (WHO), the concentration of radon in buildings depends on:
1. The local geology such as the uranium content and permeability of the underlying rocks and soils;
2. The routes available for the passage of radon from the soil into the building;
3. The radon exhalation from building materials; and
4. The rate of exchange between indoor and outdoor air, which depends on the construction of the building, the ventilation habits of the occupants and the air-tightness of the building.
The habits of occupants also contribute greatly to variations in radon concentrations in buildings, including the amount of time spent there and which rooms are used most, according to the National Plan for Radon. It also says:
“When doors and windows are open during the day, radon is diluted with fresh air and radon levels drop. On the other hand, during the night, if the doors and windows are closed, radon levels can rise again.”
Radon enters buildings through cracks in floors or at floor-wall junctions, gaps around pipes or cables, small pores in hollow-block walls, cavity walls, or sumps or drains, according to the World Health Organization. Radon levels are usually higher in basements, cellars and living spaces in contact with the ground. However, considerable radon concentration also can be found above the ground floor.
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 three months, says the World Health Organization.
Residential radon levels can be measured in an inexpensive and simple manner by means of 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.
According to the National Plan for Radon, there are several solutions, many of them low-cost, that can be used in the rehabilitation of existing buildings and prevention in new constructions. These measures are contained in two guides prepared by the National Civil Engineering Laboratory (LNEC): Guide for mitigating the admission of radon to the interior of existing buildings and Guide for the prevention of the admission of radon in new buildings.
The National Plan says: “It is important to prevent its underground transfer into the interior of the building and/or the existence of adequate ventilation systems in order to guarantee that the concentration levels remain relatively low.
“Prevention and remediation measures are either active (using mechanical methods for ventilation and/or depressurization) or passive (not using active methods). Active methods are more expensive and more effective. They require regular checks and long-term maintenance. Passive measures include the use of impermeable barriers or the placement of grilles on walls and windows. Often, the reduction of radon concentration is achieved by the combination of several ways of mitigation. Whenever corrective measures are implemented, radon concentrations should be measured to verify that the measures have been effective.
“The implementation of preventive measures is especially important in areas of high and moderate susceptibility of exposure to radon. Protective measures in future buildings (housing or workplaces) should be foreseen in the initial planning and design phase, taking into account the fact that some construction materials may constitute sources of radon (Frutos-Puerto, et al., 2020).
“When defining an integrated protection strategy, it is necessary to ensure that prevention and existing remediation efforts are known to the public, construction companies and architects/designers and that regulatory requirements are guaranteed so that constructive solutions are adopted that prevent or minimize radon concentration in construction projects, remodeling and/or rehabilitation.”
According to the World Health Organization, some common ways of reducing radon levels in existing buildings include:
1. Increasing under-floor ventilation;
2. Installing a radon sump system in the basement or under a solid floor;
3. Avoiding the passage of radon from the basement into living spaces;
4. Sealing floors and walls; and
5. 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 percent. When radon ventilation fans are added, radon levels can be reduced even further.
The main workplaces where radon exposure can be considered occupational are mines, underground transport systems, tunnels and other underground worksites such as caves, according to the National Plan.
The occurrence of excessively high concentrations of radon inside buildings, whether houses or workplaces, is not uncommon in Portugal, according to the National Plan.
Since 2006, legislation was enacted on exposure to radon, including the definition of maximum limits of concentration indoors, within the scope of the National Energy Certification System and Indoor Air Quality in Buildings.
More recently, in 2019, the country legislated basic safety standards relating to protection against hazards resulting from exposure to ionizing radiation.
In 2020, legislation was adopted for the design and renovation of buildings with the aim of ensuring and promoting the improvement of energy performance and regulating the Energy Certification of Buildings.
The National Radon Plan says: “The proposed 2022 guidelines establish a new national reference level for the average annual concentration of radon activity in the air. The level should not exceed 300 Bq/m3 in dwellings and other buildings with high occupancy by members of the public as well as in workplaces.”
(Radioactivity is measured in units called Becquerels (Bq). One Becquerel corresponds to the disintegration of one atomic nucleus per second in a cubic meter of air.)
The World Health Organization recommends:
Establishing a national annual average residential radon centration 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.
“Outdoors, radon quickly dilutes to very low concentrations and is generally not a problem,” according to the World Health Organization. “The average outdoor radon level varies from 5 Bq/m3 to 15 Bq/m3. However, radon concentrations are higher indoors and in areas with minimal ventilation, with highest levels found in places like mines, caves and water treatment facilities.
“In buildings such as homes, schools, offices, radon levels can vary substantially from 10 Bq/m3 to more than 10,000 Bq/m3. Given the properties of radon, occupants of such buildings could unknowingly be living or working in very high radon levels.”
The National Radon Plan says: The susceptibility map defines and identifies the areas most likely to have high levels of radon, therefore, making it a valuable tool for the development of strategies, raising awareness among the most affected populations; giving the scientific community a starting point in the design of studies, and helping health authorities identify at-risk populations.
The plan continues: “Risk maps give an indication of the average levels of radon in a given area. However, they cannot be used to predict the level of radon in a building, as radon levels can vary greatly between buildings apparently identical and located in the same geological unit (Miles & Appleton, 2005).”
A partnership between the Portuguese Environment Agency (APA) and the University of Coimbra in 2020 produced the map of radon susceptibility.
To date, epidemiological studies have not confirmed an association between drinking-water from such groundwater sources as springs, wells and boreholes and an increased risk of stomach cancer, according to the World Health Organization. However, the organization recommends that screening levels for radon in drinking-water be set based on the national reference level for radon in the air, which the National Radon Plan has set at its highest recommended level (300Bq/m3).
“In circumstances where high radon concentrations might be expected in drinking water, it is prudent to measure radon concentrations,” says WHO. “Straightforward and effective techniques exist to reduce the concentration of radon in drinking-water supplies by aeration or using granular activated carbon filters.”
Neither the National Plan for Radon, the non-technical Environmental Assessment nor the Preliminary Environmental Assessment by the Agencia Portuguesa de Ambiente (APA, Portuguese Environment Agency) mentions the issue of groundwater. It is common for many residents of Central and Northern Portugal to drink water from springs, wells and boreholes.
All documents can be found on the same page where the public can comment on the National Plan for Radon.
The deadline is April 1.
The National Plan for Radon was developed by the Agencia Portuguesa de Ambiente, the competent authority of the regulatory body, taking into account the recommendations of international organizations, namely the World Health Organization, International Atomic Energy Agency, the Scientific Committee of United Nations on the Effects of Atomic Radiation and the International Commission on Radiological Protection.