Paragraph 304: The thoron should have gained a little more interest. 1) The thoron could mean a significant factor in radon measurements causing interferences in case of some detectors. 2) In some cases the thoron should not be neglected in dose estimates being a considerable part of dose due to radon isotopes (220Rn, 222Rn). Our parallel 220Rn, 222Rn measurements in dwellings and underground workplaces seem to suggest that the thoron topic should have not simplified as it is in the current statement in paragraph 304.