HC Deb 21 July 1989 vol 157 c411W
Mr. Barry Field

To ask the Secretary of State for the Environment what information he has as to the causes of radiation dose rates in certain non-granite areas being higher outdoors than indoors.

Mrs. Virginia Bottomley

Dose rates from cosmic rays are usually lower indoors than outdoors because of the shielding provided by building materials. Dose rates from terrestrial gamma rays are occasionally lower indoors than outdoors because the activity of natural radionuclides in the building materials is lower than in the ground on which the building stands.