Risk Assessment of Radon in Drinking Water (1999) / Chapter Skim
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1 Introduction
1 Introduction
Pages 23-31
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From page 23... ...
Many of the elements in the process are metals such as uranium, thorium, polonium, lead, and bismuth or alkaline earths such as radium. These elements vary greatly in solubility depending on ambient physical and chemical conditions and may go into solution or be absorbed onto organic particles or clay minerals.
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From page 24... ...
MIGRATION OF RADON A radon atom that is created deep within a grain of rock usually remains there until it decays. However, when a radon atom is created near the surface of a grain, it can recoil into the pore between grains; such radon atoms do not attach or bind to the matrix that contains the immediate precursor, radium.
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From page 25... ...
is the average increase of the indoor radon concentration that results from using water having an average radon concentration of Cw. The various sources of radon and the resulting radiation exposure pathways are shown in figure 1.2.
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From page 26... ...
. EXPOSURE TO INDOOR RADON The first four descendants of radon Typo, 2~4Pb, alibi, and Typo are also radioactive and are collectively referred to as radon decay products.
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From page 27... ...
A combination of PAEC and time is a measure of exposure expressed in joule-seconds per cubic meter (I s mob. ABSORBED DOSE FROM INDOOR RADON A person in a room will inhale radon decay products that are suspended in air.
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From page 28... ...
Recent epidemiologic evidence suggests that inhalation of radon decay products in domestic environments could also be a cause of lung cancer (National Research Council 1999; Lubin and others 1995~. Although the studies do not specifically identify health effects at low doses, there is compelling circumstantial evidence that they occur.
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From page 29... ...
There was also concern regarding the dosimetry model used to estimate the risk of stomach cancer associated with radon ingestion (Harley and Robbins 1994~. As a result of those concerns, Congress intervened in 1992 and directed the administrator of EPA to prepare a multimedia risk assessment and cost estimates for compliance with regulations regarding radon in drinking water.
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From page 30... ...
CHARGE TO THE COMMITTEE The Committee on the Risk Assessment of Exposure to Drinking Water in the National Research Council's Board on Radiation Effects Research began deliberations in July 1997. The specific tasks assigned to the committee were: · To examine the development of radon risk assessments for both inhalation of air and ingestion of water.
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From page 31... ...
It includes a discussion of radon concentrations measured in outdoor air throughout the United States and an estimate of a national annual average concentration of ambient radon. Chapter 3 describes the transfer coefficient that expresses the increase in indoor airborne radon in reference to the concentration of radon in water.
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