In which areas may the radionuclides be found in drinking water?
Natural radionuclides are found both in surface water and groundwater. In the areas where drinking water is supplied from surface water, i.e. abstracted from Lake Ülemiste (incl. Kesklinna, Lasnamäe, Mustamäe, Põhja-Tallinna, Kristiine and Haabersti city districts), the content of natural radionuclides is very low.
In the areas consuming groundwater (incl. Nõmme, Maardu, Saue, Tiskre, Pillado, Pirita, Merivälja and Pärnamäe), the content of natural radionuclides is higher, and in some areas exceeds the set values by 2 to 4 times.
What is the maximum permitted content of radionuclides in drinking water?
The amount of radionuclides is converted into effective dose. It is worth noting that the effective dose per person is calculated based on a daily drinking water consumption of up to 2 litres and the annual consumption of 730 litres. If the actual consumption is lower, the radiation dose likely to be received is lower, too. Only the amount of water drunk will be taken into account, all other means of consumption – such as taking a shower – are not considered.
In Estonia, the effective dose that is established as an indicator parameter with the Minister of Social Affairs Regulation No 82, is 0.1 mSv a year.
According to that regulation, upon exceeding the limit concentrations set for the drinking water a health risk assessment shall be carried out, and if the higher parameters do not expose any risk to human health, this water may be consumed as a drinking water.
Why was the Cambrian-Vendi groundwater body chosen for the drinking water abstraction?
Extensive exploitation of groundwater abstracted from the Cambrian-Vendi aquifer on drinking purposes started in Estonia in 1950s, on the reasons that this aquifer has a good chemical composition and is extremely well protected (by a 70 m deep rock layer) from any soil pollution. The drinking water was compliant with all the standards then in force, incl. those set for the effective dose, which was 10 times lower than the indicator parameters we have today.
Can the radionuclides put my health at risk?
According to the risk assessment that was carried out by the Radiation Safety Department of the Environmental Board in 2010, a health damage of random nature arising from the presence of radionuclides in water is unlikely. Based on the calculations that were done by using the radiation safety assessment and optimization models, the maximum number of persons who could be theoretically taken ill in case of receiving the highest effective dose from the consumption of water throughout their lifetime is 0.7 from the total number of consumers. At the same time, one in eight smokers develops lung cancer throughout their lifetime and as many as 2 000 people in Estonia are injured in traffic accidents every year.
There is no place without any radioactivity in the environment that surrounds us. A person gets constantly radiation doses from the natural (gamma rays from the ground, food, drinking water, radon in residential buildings) as well as artificial sources (medical procedures). For instance, one chest x-ray gives a person radiation dose that equals to the amount of radiation that could be potentially received from drinking water within one year.
What kind of studies and analyses have been done?
In order to assess the impact of radioactivity on the consumer health, the Health Board together with the Radiation Safety Department undertook a risk assessment of drinking water in the borewells of Nõmme, Maardu, Saue, Tiskre, Pillado, Pirita, Merivälja, Pärnamäe and Keila.
The risk assessment results showed that a health damage of random nature arising from the presence of radionuclides in water is unlikely. However, as a precaution, the Health Board suggests that a bottled water is used in these areas for preparing the infant formulas.
What is being done to improve the groundwater quality and reduce the content of radionuclides?
We constantly take samples to monitor the drinking water quality, and more than 99% of these quality parameters comply with the EU standards. We have installed filters to improve and maintain the groundwater quality in all our pumping stations in use.
We use groundwater from the Ordovician-Cambrian and Cambrian-Vendi aquifers to produce drinking water, so our borewells may abstract water from different aquifers. The effective dose of radionuclides that is received from the groundwater abstracted from the Ordovician-Cambrian aquifer is within the standards recommended by the EU, it is the effective dose received from the groundwater abstracted from the Cambrian-Vendi aquifer that creates concern. Because the groundwater is a limited resource, we mix the water abstracted from both aquifers to lower the effective dose. Unfortunately, there are not enough water resources in the Ordovician-Cambrian aquifer to supply the residents in the groundwater areas with groundwater that has been abstracted from this aquifer only, or to lower the effective dose abstracted from the Cambrian-Vendi aquifer to meet the recommended standard.