Natural radiation in New Zealand houses

In addition to the natural gamma terrestrial and cosmic, radiation and the dose from inhalation of radon daughters, the New Zealand population is exposed to the natural gamma and beta radiation from radioactive materials in the body, predominantly potassium-40. The dose from this source varies slightly because the average potassium concentration in human tissue varies slightly with age and sex, but the average annual effective dose equivalent is 180 μSv from all natural radioactivity in the body. Apart from natural source of radiation, the population is also exposed to radiation from artificial sources. This is predominantly medical diagnostic x-ray. Averaged over the population, there is a much smaller component from other medical radiation, and very small components from occupational exposure and from nuclear weapons testing fallout. The annual effective dose equivalent from all these sources and their relative significance is illustrated. It is apparent that the New Zealand population receives only a small proportion of radiation from other than natural sources. When the variations in natural radiation levels revealed by this survey are considered, it is evident that concern about the much smaller levels of artificial radiation dose rates from some sources is quite misplaced. 30 refs., 5 figs., 13 tabs., ills