ABSTRACTIn December 1984, the Pennsylvania Bureau of Radiation Protection found itself confronted with the discovery of a home in eastern Pennsylvania having the highest level of radon daughters ever reported. The Bureau responded with a massive radon monitoring, educational, and remediation effort. As of November 1986, over 18,000 homes had been screened for radon daughters; of which, approximately 59% were found to have levels in excess of the 0.020 Working Level guideline. Pennsylvania's response to the indoor radon problem is detailed in this article.
As with most state radiation control programs, Pennsylvania recognized that naturally occurring radon gas was a potential indoor air pollution problem in geologic areas with elevated levels of uranium ore. It was also recognized that other states had already been working to resolve the problem for specific areas in their respective states. It was generally believed that the most significant problems were located in areas where man had enhanced the uranium environment, such as the Grand Junction area of Colorado where uranium mill tailings had been used for fill around newly constructed or remodeled buildings.
Elevated levels of radon were also reported from other areas of the country. Florida had a serious problem on phosphate lands, Montana had detected elevated levels in the Butte area, and Pennsylvania and other states had experienced elevated radon levels in the vicinity of uranium and radium extraction facilities. The U.S. Department of Energy had designated certain sites for decontamination and remedial action at facilities operated for the federal government during and after the Manhattan Project days.
In the late 70's, Pennsylvania Power and Light Company, a utility operating in central Pennsylvania carried out a study involving radon measurements in homes of their employees to determine if weatherization programs were effective. Radon was selected because of the relative ease of measurement. To their surprise, elevated radon levels were found in some homes, but there appeared to be no correlation between radon levels and home construction or location. The data were reported to the Pennsylvania Bureau of Radiation Protection (Bureau), and plans were made to begin a pilot project to determine radon levels in other areas of the state. The March 1979 Three Mile Island accident caused a major change in Bureau priorities and the survey was placed on the back burner. Plans were again made in 1984 to begin a modest survey program in the 1985-86 fiscal year as outlined in the annua1 budget submitted to the Pennsylvania General Assembly by Governor Thornburgh.
We did not have to wait that long. In December 1984, the Bureau received a telephone call from the Health Physicist at the Limerick Nuclear Generating Station informing us that a construction worker at their still incomplete plant was setting off alarms when he attempted to enter the plant through portal radiation monitors. Since the plant was not yet generating fission products, health physicists from the utility and their consultant performed a radiation survey in the home of the individual and found very high levels of radon daughters throughout the structure. Radon daughter levels (concentration of decay products of radon in the uranium chain) ranged up to 13 Working Levels (WL) or 2600 pCi/ L of radon gas.
Numerous resurveys verified those findings, and estimates of exposure and risk of lung cancer were attempted. A search of the literature on radon and radon daughter concentrations in residential structures made us aware that this was the highest level ever found in a private residence. The National Council on Radiation Protection and Measurements (NCRP) had issued two reports on radon and radon daughter exposures in April 1984, and these two documents were used to estimate the exposures of the residents of the home. The dose equivalent rate to the bronchial epithelium of the lung from continuous exposure to radon daughter concentrations of 13 WL was calculated to be 9100 rem annually. The risk of lung cancer from continuous exposure to 13 WL in one year is 0.13 or 13 chances out of 100.
A decision was made to officially recommend that the occupants vacate the residence, and a formal recommendation was made by a hand-carried letter signed by the Secretary of Pennsylvania Department of Environmental Resources. The Philadelphia Electric Company and Bechtel, Inc., the contractor employing the individual, assisted in providing living arrangements for the family until remedial action could be taken in the home.
Assuming this was not an isolated case, the Bureau designed a house-to-house campaign to evaluate radon levels in the immediate neighborhood. Unfortunately, there were and are no standards for exposure to radon or radon daughters for the general population. NCRP recommends an annual exposure guideline of 2 WL Months/yr., which corresponds to a continuous exposure guideline of 0.04 WL. Other guidelines have also been used. The Environmental Protection Agency (EPA), with assistance from the Centers for Disease Control (CDC), has recommended remedial action at 0.02 WL. The Pennsylvania Department of Health requested assistance from CDC in determining such guidance. One WLM per year or 0.02 WL continuous occupancy was received as guidance, with a sliding time scale for remedial action based upon levels detected. Table I was utilized as guidance to homeowners.
OBJECTIVE. To reduce radon daughter exposure levels to .02 Working Levels (WL) or less, if possible, through corrective action.
| If your home measures* | Suggested Action** | Time Frame for Plan |
|---|---|---|
| more than 5.0 WL | Residents should either promptly relocate or undertake temporary remedial action to lower levels as far below 5.0 WL as possible. Smoking in high areas discouraged. | Within 2-3 days |
| 1.0 to 5.0 WL | Residents should undertake temporary remedial action to lower levels as far below 1.0 WL as possible. Smoking in high areas discouraged. | Within 1 week |
| 0.5 to 1.0 WL | Residents should undertake temporary remedial action to lower levels as far below 0.5 WL as possible. | Within 2 weeks |
| 0.1 to 0.5 WL | Residents should undertake temporary remedial action to lower levels as far below 0.1 WL as possible. Higher exposure levels require action to be taken in a shorter period of time. | 3 weeks to 3 months |
| 0.02 to 0.1 WL | Residents should undertake temporary and/or permanent remedial action to lower levels below 0.02 WL. Higher exposure levels require action to be taken in a shorter period of time. | 4 to 15 months |
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The door-to-door survey campaign revealed additional homes with elevated levels, some in excess of 1.0 WL, but none as high as the first reported home. Air samples were taken in the basement of the home, or the lowest possible living space, to perform screening on as many homes as possible. Alpha-track radon monitors were also placed in the home to determine average levels. Over 2600 homes were visited and levels in excess of 0.02 WL were found in approximately 50 percent of the cases (Table 2). Data obtained from the home surveys is confidential and will be released only with the homeowner's consent. Schools and other public buildings were also surveyed. with only a few found to be above 0.02 WL.
| Alpha-track Radon Monitor Reading | No. of Homes Surveyed | Percent | Cumulative Percent | |
|---|---|---|---|---|
| All greater than 0.020 WL | Above 1.0 WL | 19 | 0.7 | 49.8% |
| 0 500 to 0.999 WL | 29 | 1.1 | ||
| 0.100 to 0.499 WL | 260 | 9.8 | ||
| 0.050 to 0.099 WL | 334 | 12.6 | ||
| 0.021 to 0.049 WL | 675 | 25.6 | ||
| All less than or equal to 0.020 WL | 0.010 to 0.020 WL | 732 | 27.7 | 50.2% |
| 0.000 to 0.009 WL | 593 | 22.5 | ||
| Total Number of Homes Surveyed = 2641 | ||||
The immediate area in question was located in Berks County in eastern Pennsylvania. Geologists have located a formation known as the Reading Prong which contains elevated levels of uranium and thorium. In the 1970's, the U.S. Department of Energy (DOE) performed an aerial radiation survey of the area in an attempt to locate potentially, recoverable uranium resources. Pennsylvania geologists, under a grant from DOE, have performed a road survey and planed environmental radiation levels on a map of the area. The Reading Prong extends from east of Reading through three counties to Easton and on into New Jersey, New York and parts of New England.
We requested and obtained assistance from the EPA Office of Radiation Programs for additional equipment, performing house-to-house surveys, and laboratory assistance in evaluating radon levels in well water supplies. DOE supplied a helicopter to perform a detailed aerial gamma radiation survey of the initial township, and a monitoring van from their Oak Ridge National Laboratory in Oak Ridge, Tennessee to determine whether ground surveys could identify high radon houses. It was found that background radiation in the area was too high to distinguish a house with high concentrations from the background radiation levels. The aerial surveys were very helpful in determining areas where homes might have high radon concentrations, but the cost was too great for a massive survey.
Remedial techniques were not well understood and the literature was confusing. Pennsylvania hired a consultant from Colorado to perform detailed radon diagnostics in 25 homes, provide potential remediation strategies for the homes, and provide a generic document that could be used by homeowners across the Commonwealth to correct their radon problems.
A fact sheet on radon was prepared with the assistance of the Pennsylvania Department of Health's Environmental Health staff, and public meetings were held in the areas being surveyed in an effort to provide as much information to the public as possible. A Spanish version was prepared and a contract with an area Spanish Community organization was entered into to provide for public information for the Spanish speaking community in the Allentown-Bethlehem areas of the state.
A Bureau office was established in the vicinity of the survey area and personnel from other Bureau activities were reassigned from their regular duties to perform radon surveys. Over $1 million was spent in the first six months of the program.
An additional $1 million was placed in the budget for radon testing during fiscal 85-86, and 20 new positions were established to perform surveys. A toll-free radon hot-line was set up to answer questions from the public and to schedule survey visits.
EPA had established a research and development program on low-cost remediation techniques and diverted the program to the Reading Prong area where 18 houses were remediated in a demonstration project.
We requested additional assistance from EPA, realizing that other Reading Prong situations must exist in other areas throughout the U.S. Low-cost screening methods, protocols for measurements, training for staff and remedial contractors, and a formal comparison procedure for different monitoring systems and techniques have been established by EPA.
Since the house-to-house survey program was very personnel-intensive and exceeded the staff time available, and since less than 30 percent of the homeowners in the area were requesting surveys, a new screening method was devised. The Reading Prong does not follow political or other boundaries, so the area of the Prong was included in expanded boundaries which could be easily distinguished. Ads were placed in newspapers in the three-county area showing a map and a list of the townships included in the expanded coverage area. A free mail-order alpha-track monitor would be sent to any resident of the area who mailed the Bureau a coupon, which was included in the ads.
Approximately 25,000 requests were received, and monitors were mailed to over 21,000 households. The results obtained to date are listed in Table 3. Over 60 percent of the homes have screening values in excess of 0.02 WL.
| Alpha-track Radon Monitor Reading | No. of Homes Surveyed | Percent | Cumulative Percent | |
|---|---|---|---|---|
| All greater than 0.020 WL | Above 1.0 WL | 83 | 0.5 | 60.3% |
| 0 500 to 0.999 WL | 136 | 0.9 | ||
| 0.100 to 0.499 WL | 1689 | 10.9 | ||
| 0.050 to 0.099 WL | 2492 | 16.0 | ||
| 0.021 to 0.049 WL | 4973 | 32.0 | ||
| All less than or equal to 0.020 WL | 0.010 to 0.020 WL | 3799 | 24.4 | 39.7% |
| 0.000 to 0.009 WL | 2372 | 15.3 | ||
| Total Number of Homes Surveyed = 15,544 | ||||
Because the method is to screen potentially high homes, the monitors were to be placed in basements, the areas of the homes with the highest potential for radon accumulation. Those homeowners with screening levels between 0.02 and 0.1 WL are sent another alpha-track monitor to be placed in the living quarters for a year to determine annual average levels of exposure.
Those in excess of 0.1 WL are visited by our staff for more detailed evaluations and recommendations are made for remedial action. Charcoal canisters are now being used instead of the air sample method because of increased reliability of data.
Following the current campaign in the expanded Prong, additional screening studies will be carried out in Pennsylvania to determine if other clusters or extended areas of elevated radon do exist. Private monitoring firms have reported finding homes with high concentrations in areas outside the Prong, and Pennsylvania geologists are evaluating other areas.
For the 1986-87 fiscal year, $1.3 million has been approved in the Department's budget for radon studies, and an additional $1 million for a remedial action demonstration project was passed by the legislature. It is anticipated that over 100 homes will undergo remedial measures free of charge in an attempt to prepare a more detailed and lower cost remedial guide for the homeowner.
A low-interest loan program has also been established to assist homeowners in funding remedial actions in their residences. For schools and other public buildings, the Department has hired a consultant to provide detailed plans for remediation. Very few public buildings have been found to have significant problems because of construction techniques and the requirements for a certain number of air changes per hour as standard practice.
Argonne National Laboratory, with funding provided by the U.S. Department of Energy, is conducting an epidemiological study of residents of the area to determine if the incidence of lung cancer in non-smoking females in the eastern 40 percent of Pennsylvania is related to their radon exposures. Present data are not precise enough to identify any such increase.