Natural radiation in the urban environment.

Summarizes previous work on natural background radiation levels and reports some new data from Boston Mass. Gamma dose rates, corrected for cosmic radiation, were measured with large ionization chambers: dose rates inside wooden single-family dwellings were 25 to 50% lower than those outside; in masonary multiple-family dwellings, they were about 10% lower.< Concentrations of radon daughters in the air were measured by predecay and postdecay alpha spectrometry: concentrations in dwellings were comparable with outdoor concentrations, but concentrations in basements were higher by a factor of about 5. Concentrations in office buildings were quite low, the radon daughters being removed by the ventilation system. Discusses effects of building type, construction materials and ventilation on human dose.