RADNET's stations are sparsely distributed, following a geographical layout based on the principle of ensuring a good coverage of the border with Spain and of the major population centres in mainland Portugal and the Autonomous Regions of Madeira and the Azores.
Radiological control of the environment
Radioactivity is neither a recent phenomenon, nor exclusively the result of anthropogenic actions. In fact, the Earth has always been subject to cosmic radiation and its constitution has always included a series of radionuclides (unstable form of a nuclide that releases energy in the form of ionising radiation to become stable). NNowadays, after the discovery of radioactivity and its subsequent use in several areas of activity, the radionuclides found in the environment can have either a natural or an anthropogenic origin. Essentially, they result from four different sources:
- Radon (Rn) exhalation into the atmosphere, 222Rn and 220Rn, produced by the radioactive disintegration of radium (Ra), 226Ra and 224Ra (natural constituents of soils and rocks) belonging to the natural radioactive series of 238U and 232Th, respectively. A good example of which is the occurrence of lead (210Pb) descendent of a long term disintegration of 222Rn;
- Formation of cosmogenic radionuclides such as beryllium (7Be), through the interaction of cosmic radiation with atmospheric gases containing carbon, nitrogen and oxygen;
- Technologically enhanced natural radiation, resulting from the industrial use of raw materials containing natural radionuclides;
- Artificial radionuclides, fission and activation products, due to anthropogenic activities (nuclear tests, electricity production in nuclear power plants, radioisotope production, accidents, among others).
Regardless of their origin, radionuclides can be present in the atmosphere in the gaseous or particulate form (associated with atmospheric aerosol). Usually, the particulate form is the one that poses the most significant radiological risk, since these particles interact with the biosphere through atmospheric transport and deposition processes.
Radiation exposure can affect human health, namely through genetic modifications and the development of different types of cancer (leukaemia, lung cancer, skin cancer, stomach cancer, others.). Exposure can be direct (namely via human exposure to the source) or indirect, via the environment (air, water, soil, food) due to the accidental introduction of those substances into the environment.
The radiological environmental surveillance in Portugal, is responsibility of Portuguese Environmental Agency (APA) and carried out through monitoring programmes designed to assess the presence of artificial and natural radionuclides in environmental compartments (atmospheric, aquatic and terrestrial), which represent direct contamination pathways for Man.
Portugal has been operating, since 1989, an Alert Radiological Monitoring Network (RADNET) capable of detecting situations of abnormal increase in radioactivity in the environment. In recent years, all older RADNET stations have been replaced by newer versions able to, in addition to measuring gamma radiation dose rates (in the quantity of H*(10)), also identifying the radionuclides present in the environment, allowing better identification of the potential source of any unexpected increase in radioactivity and increasing the sensitivity of the network.
This network, continuously measuring gamma radiation in the air and in the main international rivers (Tejo, Douro and Guadiana), includes several measuring stations spread across the mainland and autonomous regions, with the aim of ensuring good coverage of the border area with Spain, of large population centres in Portugal and of places relevant to the transit of radioactive materials. Currently has 17 fixed stations for measuring radiation in the environment and three fixed stations for measuring gamma radiation in water.
If necessary, this network can be completed with a station installed in a vehicle and two portable stations, which can be temporarily installed anywhere in the territory, all of them capable of measuring gamma radiation dose rates (in the quantity of H *(10)).
The network continuously measures gamma radiation in the environment and in water, triggering alarms when measured radiation levels exceed pre-defined thresholds. In these cases, the alarm received at the central unit will trigger the automatic, audible and visual systems installed at APA, which is responsible for managing RADNET.
New radioactivity monitoring stations are currently being tested, one for monitoring radioactivity in the air (with the ability to identify the radionuclides present in the environment and to measuring gamma radiation dose rates, in the quantity of H*(10)) to be installed in the north of the district of Viana do Castelo, and three stations for monitoring aerosols and radioactive iodine installed in Vila Real, Abrantes and Évora, allowing the expansion and diversification of this network. As soon as the testing phase is completed, the values of these new stations will be made available to the public as is already the case for the other stations.
In addition to the RADNET, there is radiological monitoring of the environment based on samples of aerosols, surface waters, food chain components and complete meals. Currently, this monitoring is carried out by Laboratório de Proteção e Segurança Radiológica (LPSR) of Técnico Lisboa.
This fact sheet concerns mainland Portugal and the Autonomous Regions of Madeira and the Azores and will be updated whenever new data becomes available.
- Ensure that the RADNET is operational, allowing an immediate notification in the event of the detection of abnormal values and proceed with a prompt and well-coordinated response at national level;
- Ensure the routine monitoring of environmental radiation and the identification of deviations in values with radiological relevance.
Location of the RADNET 2021 stations

Annual average values of the ambient gamma radiation dose rate in Portugal, between 2010 and 2020
With regard to the annual average values of the environmental gamma radiation dose rate, the data collected between 2010 and 2020 corresponds to values of the natural radioactive background of the measurement site. This natural radioactive background varies according to local geology and altitude, explaining the fact that the annual average values obtained in distinct stations are considerably different.
It is also possible to observe that the annual averages for each station have remained constant over the mentioned years, allowing the conclusion that there were no significant changes in the levels of environmental gamma radiation, referring to a normal situation from the radiological point of view.
Additionally, it is also possible to verify the reduction of annual average values in 2019 and 2020 for some stations, which results from the change of equipment to more sensitive systems, aiming to increase the ability to detect small variations in the levels of gamma radiation in the environment.
The activity present in the atmosphere has been controlled through the continuous sampling of aerosols, at the Campus Tecnológico e Nuclear of Técnico Lisboa, where is located the Portuguese Research Reactor (RPI), currently inactive and awaiting the start of the dismantling process.
Evolution of activity concentration in Beryllium-7 and Lead-210 (mBq m-3) and in the concentration of suspended particles (μg m-3) in aerosols collected at the Campus Tecnológico e Nuclear between 2010 and 2019

According to 2019 measurements, the monthly average concentration of total suspended particles (PTS) ranged from 21 μg m-3, in October, to 64 μg m-3, in May.
The monthly average activity concentration in 7Be ranged from 2.09±0.21 mBq m-3 to 7.01±0.71 mBq m-3, showing an annual average value of 4.9±1.7 mBq m-3.
In the case of 210Pb, the monthly average activity concentration ranged from 0.122±0.035 mBq m-3 to 0.65±0.10 mBq m-3, with an annual average value of 0.41±0.17 mBq m-3.
The variation in the monthly and annual average concentration for radionuclides detected in aerosols and for total suspended particles (PTS) in the last few years is within the expected limits.
This data does not show any abnormal values or risks for the population and the environment and indicates that the RPI has not been contributing toward any deterioration in air quality at the monitoring site.
Radioactivity in surface waters can be caused by radionuclides dissolved in the aqueous phase and/or by radionuclides adsorbed on suspended particles, which may occasionally be incorporated in sediments and living organisms. In addition to radionuclides of natural origin, such as uranium, thorium, radium, radon and its descendants, and it may also be possible to detect tritium (3H) and the radionuclides caesium (137Cs) and strontium (90Sr) (usually of anthropogenic origin). These radionuclides are activation and fission products resulting from the operation of nuclear power plants. The radionuclide 3H can be released into the environment under normal conditions and/or after a nuclear accident while 137Cs and 90Sr are present in the environment only due to nuclear or radiological accidents and nuclear tests or explosions.
Values of activity concentration in Cesium-137 and Strontium-90 (Bq L-1) in surface water collected in the river Tagus (Vila Velha de Ródão) between 2010 and 2017

The surveillance of radioactivity from radionuclides with an anthropogenic origin, 137Cs, 90Sr and 3H, in surface waters has also been ensured in the rivers Tejo, Zêzere, Douro, Mondego and Guadiana by the LPSR.
In the river Tejo, the surface water sampling is carried out on a monthly basis in Vila Velha de Ródão, collecting simultaneously samples of sediments, fishes and aquatic plants.
The activities in 137Cs and 90Sr in surface waters, in Vila Velha de Ródão, have remained relatively constant, without any major variations from one year to the next. It should be noted that, in some 137Cs and 90Sr determinations, the values obtained are lower than the detection limits of the technique that is being used. For that reason those values are represented with no uncertainty.
Values of activity concentration in Tritium (Bq L-1) in surface waters collected in the river Tejo (Vila Velha de Ródão and Valada do Ribatejo) and in the river Zêzere (Castelo de Bode Dam) between 2010 and 2019

The activity in 3H, also in Vila Velha de Ródão, has varied throughout the months and the years. In 2015, the variation throughout the year was quite pronounced, having reached the highest value in September/October. In 2019, the values were similar to 2018, with higher values in March/May in V. Velha de Ródão and in June/July in Valada do Ribatejo. The variation observed over the years may, however, be related to the normal operation of the Almaraz Nuclear Power Plant, located in Spain, whose effluents are discharged into the Tagus River and with the discharge system from the water dams along the river. The analysis of the chart indicates activities below the limit values for the population and the environment.
Evaluation the radioactivity in the mixed diet
The assessment of the level of radioactivity in the mixed diet gives an indication of the potential radioactive contamination to humans via the food chain. This evaluation is performed by the analysis of individual food products or complete meals, being complete meals more representative of the mixed diet.
According to the data from the current Environment Radioactivity Monitoring Programme (text in PT only), the results of the radiological control of the food products considered as the main constituents of the Portuguese diet (mixed diet) show a rather low level of artificial radioactivity.
From the broad range of results (text in PT only) obtained from 2010 to 2019 we conclude that the radioactivity levels fall within the range of the values obtained in previous years. The activity concentrations of radionuclides of natural origin, namely from the uranium, thorium and potassium-40 (40K) families, are typical values of the natural radioactive background, i.e., not changed by human activity. The activity concentrations of radionuclides of artificial origin, namely 137Cs, 90Sr and 3H, are very low and usually below the minimum detectable activity values.
The nationwide results of the radiological monitoring of the environment (text in PT only) obtained for different types of samples (aerosols, rainwater, surface waters, waters for human consumption, food products, milk, sediments, soils, among others) between 2010 and 2019 are low and within the range of values obtained in previous years.
Portuguese Environment Agency – https://apambiente.pt/prevencao-e-gestao-de-riscos/protecao-radiologica
National Environmental Information System (SINAmb): Monitoring Indicators – sniamb.apambiente.pt/Home/Default.htm
Environmental Radioactivity Alert Network - radnet.apambiente.pt/
EURDEP Platform - eurdep.jrc.ec.europa.eu/Basic/Pages/Public/Home/Default.aspx
Laboratory of Radiological Protection and Safety - www.itn.pt/sec/psr/