The HSE has confirmed that they are to test six Irish citizens in relation to the recent Polonium-210 incident in London.
The substance was used to poison ex-KGB agent Alexander Litvinenko in London last month.
The HSE said the tests were being carried out as a precaution and in line with good public health practice after they had received details from UK authorities about the individuals.
The executive said it will carry out the tests in conjunction with the Department of Foreign Affairs and the Radiological Protection Institute of Ireland (RPII).