The American Water Works Association (AWWA) has urged U.S. water utilities to begin monitoring for radon ahead of pending U.S. Environmental Protection Agency regulations so that they can adequately evaluate the possible health risks associated with radon in drinking water and determine potential compliance strategies.
"While USEPA radon regulations are not slated for proposal until August 1999, utilities should take monitoring steps now," said AWWA President Rod Holme. "By taking early action on radon, utilities will be able to collect sound data on radon health effects and have sufficient time to determine the most appropriate and cost-effective treatment method."
EPA recently released its Health Risk Reduction and Cost Analysis (HRRCA), which will be used to support development of a National Primary Drinking Water Regulation (NPDWR) for radon in drinking water, as required by the Safe Drinking Water Act (SDWA).
Although drinking water accounts for only a fraction of radon accumulation in homes, there is a possibility that drinking water with high levels of radon could constitute a health threat, and even this slight threat is important to address, said Holme.
"AWWA feels strongly that this action is necessary to protect public health while the regulations are being finalized," he said.
According to the National Academy of Sciences (NAS), radon in indoor air from all sources causes approximately 12 percent of lung cancers, and radon in indoor air attributable to drinking water causes approximately 0.1 percent of lung cancers. Cigarette smoking, however, causes the vast majority of lung cancers.
Utilities that do not begin monitoring now might be faced with a compressed time frame for determining a compliance strategy and meeting the impending regulation, Holme said. Also, utilities may experience delays when developing and installing an appropriate treatment design because technologies for removing radon are not yet fully developed. Air-quality permitting delays and insufficient laboratory analysis capabilities may also cause delays.
AWWA recommends that utilities with radon levels above 4,000 pCi/l begin treatment. This recommendation dovetails with a recent National Academy of Science report that endorsed an alternative maximum contaminant level of 150,000 Bq/m3 (4,000 pCi/l). EPAs health risk study evaluated groundwater radon levels of 100, 300, 500, 700, 1000, 2000, and 4000 pCi/l.
EPA has said its goal for the HRRCA is to provide a neutral and fact-based analysis of the costs, benefits, and other impacts of controlling radon levels in drinking water. This is the first such analysis prepared by the EPA under SDWA. As such, EPA is seeking comment on the techniques, assumptions, and data inputs upon which the analysis is based.
According to HRRCA, the costs of radon treatment per-household will be higher for smaller systems. However, costs should remain relatively constant across different radon levels within each system size category. For example, for large systems the cost of treatment was projected to be between $6 and $7 annually per household, no matter what the level of radon in the water. That compares with $10 to $11 per year for medium size systems and $19-$20 for small systems.
Under baseline assumptions (no control of radon exposure), approximately 160 fatal cancers and 9.2 non-fatal cancers per year are associated with radon exposures through community water systems, according to the NAS report. Using treatment to reduce radon levels to below 4,000 pCi/l would prevent approximately 2.2 fatal cancers and 0.1 non-fatal cancers per year. Reducing radon to the lowest level evaluated, 100 pCi/l, would prevent approximately 115 fatal and 6.6 non-fatal cancers per year.
When figuring the cost of treatment, EPA included a number of aeration and granular activated carbon (GAC) technologies, as well as storage, regionalization, and disinfection as a post-treatment. To estimate costs, water systems were assumed, with a few exceptions, to select the technology that could reduce radon to the selected target level at the lowest cost.
EPA found that some technologies used to remove radon from drinking water also carry a risk. As an example, some groundwater systems that currently do not disinfect may begin to do so as part of their radon treatment program. EPA realizes that adding chlorine for disinfection may result in a risk-risk tradeoff because of the increased exposures to disinfection by-products (DBPs).
Radon Gas
In general, radon levels in ground water in the United States have been found to be the highest in New England and the Appalachian uplands of the Middle Atlantic and Southeastern states. There are also isolated areas in the Rocky Mountains, California, Texas, and the upper Midwest where radon levels in ground water tend to be higher than average. The lowest ground water radon levels tend to be found in the Mississippi Valley, lower Midwest, and Plains states.
Radon Gas
Radon is a naturally occurring volatile gas formed from the normal radioactive decay of uranium. It is colorless, odorless, tasteless, chemically inert, and radioactive. Uranium is present in small amounts in most rocks and soil, where it decays to other products including radium, then to radon. Some of the radon moves through air or water-filled pores in the soil to the soil surface and enters the air, and can enter buildings through cracks and other holes in the foundation.
Radon Gas
Some radon remains below the surface and dissolves in ground water. When that water is piped into a home, it can be consumed with the water or released into the air when the water is dispensed.
Radon Gas
Exposure to radon and its progeny is believed to be associated with increased risks of several kinds of cancer. When radon is inhaled, lung cancer accounts for most of 9 the total incremental cancer risk. Ingestion of radon in water is suspected of being associated with increased risk of tumors of several internal organs, primarily the stomach.
Radon Gas
As required by the SDWA, EPA arranged for the National Academy of Sciences (NAS) to assess the health risks of radon in drinking water. The NAS released the "Report on the Risks of Radon in Drinking Water," in September 1998. The NAS report represents a comprehensive assessment of scientific data gathered to date on radon in drinking water. The report, in general, confirms earlier EPA scientific conclusions and analyses of radon in drinking water.
Radon Gas
NAS recently estimated individual lifetime unit fatal cancer risks associated with exposure to radon from domestic water use for ingestion and inhalation pathways. The results show that inhalation of radon progeny accounts for most (approximately 89 percent) of the individual risk associated with domestic water use, with almost all of the remainder (11 percent) resulting from directly ingesting radon in drinking water. Inhalation of radon progeny is associated primarily with increased risk of lung cancer, while ingestion exposure is associated primarily with elevated risk of stomach cancer.
Radon Gas
The NAS Report confirmed that indoor air contamination arising from soil gas typically account for the bulk of total individual risk due to radon exposure. Usually, most radon gas enters indoor air by diffusion from soils through basement walls or foundation cracks or openings.
Radon Gas
Radon in domestic water generally contributes a small proportion of the total radon in indoor air.
Radon Gas
The NAS Report is one of the most important inputs used by EPA in the HRRCA. EPA has used the NASs assessment of the cancer risks from radon in drinking water to estimate both the health risks posed by existing levels of radon in drinking water and also the cancer deaths prevented by reducing radon levels. The HRRCA builds on several technical components, including estimates of radon occurrence in drinking water, analytical methods for detecting and measuring radon levels, and treatment technologies.
