HC Deb 04 April 1955 vol 539 c74W
Mr. Mason

asked the Minister of Works what steps were taken to assess the Roentgen percentage of radioactivity in the radioactive clouds which have passed over these islands following thermonuclear explosions; what was that percentage; and to what extent, and for how long, these clouds constitute a danger.

Mr. Birch

Measurements of the radioactivity in the atmosphere at various heights show that no danger has existed over these islands from thermo-nuclear explosions.