Radon in drinking water

Radon in drinking water

Given that radon easily dissolves in water, it can also enter buildings from the subsoil via water pipes. When the water is used in the household, radon can be released and decays into its radioactive decay products within the house.

There are two possibilities for radon entering the building via water pipes to lead to internal radiation exposure: While drinking radon-containing drinking water and inhaling radon which is released from hot cooking water or shower water.

Level of radioactivity in drinking waters

In a Germany-wide investigation programme, the Federal Office for Radiation Protection (BfS) examined the level of radioactivity in drinking waters, measuring, among others, radon.

The study showed that the overall exposure to natural radionuclides in drinking water in Germany is considered to be low. However, depending on the quality of the subsoil, the drinking water may have an increased content of natural radionuclides.

Limiting the radon concentration in drinking water

The level of radon in drinking water can be limited by organisational or technical measures in the waterworks – for example by mixing radon-containing water with less-radon-containing water from other sources.

It is also possible to "air" the water with oxygen: This method is generally applied in waterworks to remove iron and manganese from the water. This is done by blowing a lot of air or oxygen from below into the water basins, causing a chemical reaction of iron and manganese but also radon to leave the water while it is bubbling.

Recommendations

The German Commission on Radiological Protection recommends limiting the radon concentration in drinking water to maximum 100 becquerel per litre. The EU Drinking Water Directive and the German Drinking Water Ordinance that has been derived from it also give a recommendation on limiting the radon concentration in drinking water.

In its "Guidelines for the analysis and assessment of radioactive substances in drinking water by implementing the Drinking Water Ordinance" the BfS follows these recommendations. The BfS guidelines provide a common basis for comprehensively monitoring the water quality with regard to radioactivity-related parameters.

According to the Drinking Water Ordinance, large water supply companies are obliged to examine the concentration of radionuclides in drinking water since end of 2019. In regions with a high level of natural radon, it is planned for the water supply companies to initiate measures to reduce the radon in drinking water and to conduct further control measurements.