radon

Reports first report from committee, "Preliminary proposals for measures against radiation risks in dwellings". Notes that prime source of radiation, alum-based lightweight concrete, has been banned in new buildings in Sweden, but is still present in 10%of pre-1975 houses. Provisional limits for gamma radiation for undeveloped sites: 30-100 micro.r/h (site should only be built on subject to other conditions), more than 100 micro.r/h (building inadvisable). suggests that geological radiation maps be charted. Notes reduction in radon content through house ventilation.

Investigation has shown connection between radon content in mines and lung cancer in miners. Radon is also present in building structures. Presents measurements carried out inNorwegian houses and discusses consequences of radiation doses absorbed in human lungs as well as biological effects of background radiation. Diagram illustrates concentration of radon in concrete, brick and wood. Analyses factors which affect radon content, particularly barometric pressure and ventilation rates.

Outlines problem of radon in buildings and current state of knowledge. Suggests reduction of radon by a) more efficient ventilation, b) use of diffusion resistant films to seal wall surfaces and c) elimination of certain active materials. A research project at the Swedish Council for Building Research is currently investigating the problem.

Reports some results of field measurements of radon levels in apartments and houses and shows that summer measurements with high natural ventilation rates are generally lower than winter measurements. Suggests exhalation of radon from building materials can be studied by placing samples of material in closed vessels and following the growth of activity in the vessels. Shows that a ventilation rate of one air change per hour will lower the theoretical maximum level to 0.008 of the unventilated maximum value.

Radon is a radioactive gas which diffuses naturally from all mineral based building materials. States for most homes, concentration of radon is approximately inversely proportional to the ventilation, although this is not valid for very low or very high air change rates. Gives brief results of measurements of concentration of radon in dwellings. Outlines health risks from radon and daughters. Reviews norms laid down in some countries for specific situations. Discusses ways of reducing radon concentrations.

Awareness has developed in the United States in the last five years that traces of radioactive radon gas and its daughter products are present in varying amounts in the indoor air. Reviews the existing literature in the subject giving a table showing reported radon concentration. Notes wide variation in results. mentions standards developed to protect uranium mines. Recommends research to quantify radon concentration data.

Reports study of the ways in which different ventilation levels affect people part 1 of the study took place in Gavle. Air change rates, the amounts of radon and its derivatives were measured. Finds that ventilation installations are often poorly adjusted giving a wide variation between flats in the levels of air change. Amounts of radon and daughters were also higher than expected, due mainly to the poor ventilation. Concludes that lowering ventilation to present recommended level of 0.5 changesper hour cannot be recommended without further investigation.

Describes background to natural radiation in building materials and particular aspects of radium decay which produces radon. Notes human lung capacity to absorb airborne particles and associated health risks. Illustrates diagramatically different particle sizes retained in various sections of human respiratory system. Suggests methods to avoid exposure to decay products: avoid materials with high radium content and maintain low radon concentration through sufficient ventilation. Graph shows concentration of radon in relation to air change rate.

Reports measurements in seven groups of town house in Gavle, Sweden of concentrations of radon and daughter products. Gives results with the type of building materials, the ventilation systems and air-change rates measured using nitrous oxide as a tracer gas. Gives formula for the permitted limits of radionucleides in building materials. Discussed results and concludes that the concentration of radon does not differ significantly from single family to multi-family houses.

Notes that reduced infiltration and ventilation rates in buildings can lead to higher levels of indoor air pollution. Discusses three indoor-generated pollutants : nitrogen dioxide, formaldehyde and radon. Suggest ways of circumventing increased health risks without compromising energy conservation considerations, including setting standards for minimum levels, filtering recirculated air and sealing source material.