Radon, effects

Fukaxawa, C.A. 47, 12483e (1953). Alpha particle bombardment with radon effects the conversion of kitol to vitamin A Embree, Shantz, foe. cit. U.S. pats. 2,414,458... 

Past is prologue. We can learn that despite some mistakes in the past that, in general, the human impact of waste disposal practices have not been great. These inq>acts have also been local, i.e. they have not had global or transboundary effects. This is not to discount the seriousness of these impacts but emphasize their local character. In most other instances the impacts have been below sniall percentages of natural background minus radon effects. 

Effects of indoor air pollutants on humans are essentially the same as those described in Chapter 7. However, there can be some additional pollutant exposures in the indoor environment that are not common in the ambient setting. From the listing in Table 23-1, radon exposures indoors present a radiation hazard for the development of lung cancer. Environmental tobacco smoke has been found to cause lung cancer and other respiratory diseases. Biological agents such as molds and other toxins may be a more likely exposure hazard indoors than outside. 

As the science of indoor air quality has matured, indoor air professionals have realized that many indoor air contaminants and the associated health effects are linked to specific types of buildings and their characteristics. For example, radon is primarily an indoor air concern in homes because of the ease with which it can be transported inside residential construction from the soil beneath. On the other hand. Sick Building Syndrome (SBS) primarily afflicts office building occupants who experience acute health and comfort effects that appear to be linked to time spent in a specific building. 

National Academy of Science. (1999). Health Effects of Exposure to Radon BEIR VI, Committee on Health Risks of Exposure to Radon. Washington, DC National Academy Press. 

Radioactivity The ability possessed by some natural and synthetic isotopes to undergo nuclear transformation to other isotopes, 513 applications, 516-518 biological effects, 528-529 bombardment reactions, 514-516 diagnostic uses, 516t discovery of, 517 modes of decay, 513-514 nuclear stability and, 29-30 rate of decay, 518-520,531q Radium, 521-522 Radon, 528 Ramsay, William, 190 Random polymer 613-614 Randomness factor, 452-453 Raoult s law A relation between the vapor pressure (P) of a component of a solution and that of the pure component (P°) at the same temperature P — XP°, where X is the mole fraction, 268... 

Fleischer RL (1982) Alpha-recoil damage and solution effects in minerals uranium isotopic disequilibrium and radon release. Geochim Cosmochim Acta 46 2191-2201 Fleischer RL (1988) Alpha-recoil damage relation to isotopic disequilibrium and leaching of radionuclides. Geochim Cosmochim Acta 52 1459-1466... 

Lefuma J, Chameaud J, Perraud R, et al. 1976. [An experimental study on a comparison between the toxic effects of radon-222 and its daughters on the lungs, and those exerted by alpha-emitters of the actinium series.] Occup Saf Health Ser 32 43-53. (French). 

BEIRIV. 1988. Health risks of radon and other internally deposited alpha emitters. Committee on the Biological Effects of Ionizing Radiations, National Research Council. Washington, DC National Academy Press. 

James A. 1987. A reconsideration of cells at risk and other key factors in radon daughter dosimetry. In Hopke P, ed. Radon and its decay products Occurrence, properties and health effects. ACS Symposium Series 331. Washington, DC American Chemical Society, 400-418. 

The known health effect associated with exposure to elevated levels of radon above the action or guidance level is an increased risk of developing lung cancer. The guideline levels for radon in existing homes are as follows ... 

Radon mitigation by SSD has been proven to be very effective, often decreasing indoor radon concentrations by 90% or more following mitigation. 

Another environmental effect that should not be overlooked is the amount of airflow through the fan. To remain at an appropriate operating temperature the fan requires sufficient airflow to remove fan motor heat. Fan motor capacitor failure will cause the motor to operate at a lower speed and efficiency, especially after the motor has been shut off by the occupant or electrical power interruption. Operating the fan in either of these modes will lead to higher radon levels in the living space and invites early fan failure. 

It should be pointed out that attempts to control radon by making a gastight barrier around the foundation have not been completely effective. It is likely that they have done some good, but many... 

Coatings are applied to the outside or inside of the foundation, creating a radon-resistant barrier between the source and the inside of the home. They come in a wide variety of materials including paint-like products that can be brushed on the interior of the foundation, tar-like materials that are applied to the outside, and cementitious materials that can be brushed or troweled on. They cannot be applied to the underside of the concrete floor slab for obvious reasons, so they must be applied to the inside surface of the slab. The effective life of an interior coating can be greatly diminished by damage therefore, care must be taken to provide protection to the material used. 

In theory, the application of radon barriers should be adequate to avoid elevated radon levels in houses. In practice, however, a backup radon mitigation system has been found essential for maintaining indoor radon concentrations below 4 pCi/L in most homes studied. In the recent radon-resistant residential construction projects conducted by U.S. EPA and/or private builders, several of the homes designed to be radon resistant have contained radon concentrations above 4 pCi/L. In each of those houses, a backup system consisting of an active (fan-assisted), or passive (wind-and-stack-effect-assisted), SSD system was installed at the time of construction. When mechanical barriers failed to adequately control radon, the soil depressurization methods were made operational. 

A passive system is much the same as an active system with the exception of the fan. A passive system relies only on stack and wind effects to produce the pressure field. As can be seen in Table 31.1, passive systems do not always reduce radon concentrations to acceptable levels, but careful design and installation may improve the effectiveness of a passive system. 

Theoretically, a gastight barrier could be placed between the soil and foundation to eliminate radon entry from the soil. Like many other building details, it is much easier to draw such a detail than to actually install it. Many materials form effective retarders to gas transport. The problem is effectively sealing cracks, joints, and penetrations. As anyone who has tried to build an airtight house can tell you, it is not as easy as it seems. 

Ongoing U.S. EPA research on radon-resistant new construction has encountered numerous difficulties in making a gastight mechanical barrier effective enough to confidently keep indoor radon levels below 4pCi/L. The types of problems encountered included... 

The materials used to construct a foundation can often be used as an effective barrier to the entry of radon-laden soil gas. Below-grade walls may be constructed of poured concrete, masonry, or other materials such as pressure-treated wood or stone. The materials covered in this section, poured concrete and masonry block, are the materials most commonly used for new construction. Details of radon protection in permanent wood foundations can be found in an NFoPA publication.21... 

If waterproofing or dampproofing treatments that are effective gas barriers and that can be sealed at joints and penetrations could be identified, then walls could be made radon resistant. Acceptable dampproofing or waterproofing treatments are specifically listed in building codes in many areas of the United States these lists are periodically amended as new materials come into use. These coatings apply primarily to basement walls. 

Membranes of plastics and rubbers that are used to control liquid water penetration and water vapor diffusion are effective in controlling air movement as well. If they can be adequately sealed at the joints and penetrations and installed intact, then they could also provide a mechanical barrier to radon entry. 

In Sweden, subslab membranes are not required in high-radon areas and a tightly sealed slab is considered to be a more effective radon barrier. The difficulty of achieving a completely sealed, intact subslab membrane is widely acknowledged however, a subslab barrier may be worthwhile even if it is imperfectly installed. Polyethylene construction him (6-mil) can serve as a backup radon barrier to the concrete slab, even though it is not a complete radon barrier by itself. The barrier may continue to function, even with punctures, if incidental cracks and holes in the slab are aligned with intact areas of polyethylene. 

Polyethylene-based membranes are manufactured for use in hazardous waste landfills, lagoons, and similar applications. Two of these products have been tested to determine their effectiveness as barriers against radon diffusion. (In most cases, diffusive flow is considered of little or no significance as a mechanism of radon entry compared with convective flow). A 20-mil high-density polyethylene tested 99.9% effective in blocking radon diffusion under neutral pressure conditions. A 30-mil low-density polyethylene tested 98% effective in blocking radon diffusion under neutral pressure conditions. 

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