The Phosphorus Slag Issue: Response to Public Comments | Region 10 | US EPA

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The Phosphorus Slag Issue: Response to Public Comments

U.S. Environmental Protection Agency (EPA) response to comments received during the 30 day public comment period (September 18 to October 17,1995) on the "Exposure Study Workplan" and Technical Work Group recommendations for "Graded Decision Guidelines".

EPA Response to Comments and Questions Received During Public Comment Period

Comment: How did the Technical Work Group (TWG) reach agreement on Graded Decision Guidelines given the different interests the members represented?

Response: The Technical Work Group attempted, where possible, to make recommendations based on consensus. Since the TWG reflected a wide range of perspectives the TWG products represent as much common ground as could be found.

The TWG agreed on a "graded" set of guidelines incorporating a middle range of radiation exposure levels between the recommendation for action and the recommendation for no action. In this middle range the specific circumstances and concerns of the homeowner are the primary determining factors in deciding what actions are acceptable.

Comment: What level of radiation is safe?

Response: No one knows for sure. EPA's position is that it is reasonable to assume, for radiation protection purposes, that there is no level of radiation which can be determined to be harmless to people. This position takes into account the best available evidence and the uncertainties involved. The purpose of the TWG efforts was not to resolve whether there are risks associated with slag. The purpose was to develop guidelines for what, if any, actions might be acceptable to address the risks from slag.

There is general agreement that exposure to slag causes some additional radiation exposure. Since EPA believes even small amounts of radiation carry some small risk, it also believes that there are some risks associated with exposure to slag. However, the fact that there is some risk does not necessarily mean action (such as slag removal) is always warranted in every case. EPA's goal in other radiation control contexts is an "acceptable" level of risk which also takes into consideration the practicality of actions to reduce radiation exposure.

Comment: Who will pay for the testing program and implementation of the Graded Decision Guidelines?

Response: FMC and Monsanto. These two Companies will soon sign an agreement with EPA for conducting the exposure study and taking actions to reduce individual exposures from phosphorus slag within the framework of the Graded Decision Guidelines. The Companies will also reimburse EPA and the District Health Department for their expenses during the program.

Comment: How were the 20 microrem/hr and 100 millirem/yr screening levels established?

Response: The 100 millirem/year level was selected primarily because it is a level at which it is practical to distinguish between exposures from natural background radiation and slag-influenced radiation. It is also consistent with the "widely accepted population exposure guide of 100 millirems per year in excess of natural background" noted by the Science Advisory Board (SAB) in their review of the Idaho radionuclide Study.

Radiation levels of 20 microrem/hour above background will, over the course of a year (24 hours per day, 365 days per year) result in a cumulative radiation exposure of 175 millirem for that year. It is unlikely, however, that anyone would actually remain in any one location for 8766 hours in a year. Taking "occupancy factors" into account, the 20 microrem/hour level was selected as a screening level below which it would be unlikely that anyone would actually receive 100 millirem in a year of normal occupancy.

Comment:: The focus of the exposure study seems to be the communities of Pocatello, and Soda Springs. Can individuals outside these communities participate in the testing program?

Response: Yes. Individuals in surrounding communities are welcome to participate in the program.

The focus of the TWG discussions and EPA's efforts on this issue have been on Pocatello and Soda Springs, since slag was known to have been used as a construction material for some homes in these communities. Based on previous studies exposures in a home constructed with slag may be in the range of the Graded Decision Guidelines. It is possible that there are homes or businesses outside of these two communities where slag may have been used. Therefore, the program is open to anyone that has concerns regarding possible exposure to radiation from phosphorus slag.

Comment: What do individuals need to do to have their place of employment tested?

Response: Surveys will not be performed in any location without authorization from the person responsible for the location (e.g. homeowner, building manager, business owner, etc.) If you wish to have your workplace included in the testing you should contact your employer or landlord.

Comment: What are the long-term health effects from phosphorus slag?

Response: No one really knows. Slag contains natural radioactive material at levels higher than found in most ordinary rock and soil. This radioactive material emits gamma radiation which is a type of radiation similar to medical X-rays. The primary health effect associated with gamma radiation is cancer. It is not known whether the low levels of gamma radiation associated with slag can cause cancer. Compounding this uncertainty is the fact that there may be a hundredfold difference among individuals in the way they respond to a carcinogen, such as radiation.

In the face of this kind of uncertainty scientists use risk estimates to determine what levels of exposure to a carcinogen are acceptable. For radiation protection purposes, risk estimates assume that even small amounts of radiation pose some risk. At exposures comparable to external background radiation, however, the possibility that there may be no risks cannot be ruled out.

For communities close to uranium mines where low level radiation exists, EPA recommends action when risks are increased by at least one in 10,000 over existing cancer risks. Using EPA risk assessment guidelines for radiation a 100 millirem/yr exposure represents a 30 in 10,000 excess lifetime risk of cancer. Based on previous studies an exposure of 205 millirem/yr may be possible from slag, which is equivalent to approximately a 60 in 10,000 excess lifetime risk of cancer. These risks represent small fractions of the "everyday" risk of cancer, which is approximately 2,500 in 10,000.

Comment: How much has been spent by EPA and the Companies on this issue since it was first identified as compared to the public health benefit.

Response: The EPA does not have information on how much the Companies have spent to address this issue. Since 1980 EPA has spent approximately $586,000 on the phosphate slag issue. The costs for the Idaho Radionuclide Study was approximately $700,000. These costs are associated with staff time, overhead, travel expenses, and technical support. The Companies reimburse EPA for it's expenses on this project.

Actions taken to reduce exposure, as outlined in the Graded Decision Guidelines, will reduce the risk of cancer. As yet no public health benefits have been realized since no exposure reduction measures have been implemented.

The costs to reduce risks from developing cancer vary considerably in this country depending on a variety of factors such as who bears the risk, who derives the benefit, who bears the costs, and whether it is a voluntary or involuntary risk. In a recent uranium mill tailings cleanup in Monticello, Utah, where low levels of radiation exist, $5.6 Million was spent by the Department of Energy on 101 homes to reduce radiation exposures by an estimated 119 mrem/yr.

Comment: Why was it necessary to develop Graded Decision Guidelines? Isn't there a national standard that applies to radiation exposure from phosphorus slag.

Response: There are no national standards that apply specifically to radiation exposure from phosphorus slag.

In developing the Graded Decision Guidelines, the Technical Workgroup considered a wide variety of standards and guidance for radiation protection:


Comment: Did the TWG make any decisions on potential future uses of slag?

Response: No. The Graded Decision Guidelines do not address the future use of slag, since future use of slag was not part of the charter of the TWG. The Companies no longer sell or distribute phosphate slag and have agreed to not use the material outside of their operating areas, without EPA approval. Based on current knowledge of radiation risks associated with slag EPA does not recommend use of this material for any purpose. EPA believes that the potential health benefits derived from restricting use of slag far outweigh any "benefits" from continued use.

Comment: Will all public buildings be included in the testing program?

Response: Not automatically, surveys will not be performed without authorization from the person responsible for the location. EPA encourages all local officials to request that the public areas they are responsible for be included in the program, and make the results available to the public.

Comment: Will this program affect my property value?

Response: It shouldn't, given the confidential nature of this program. If the results indicate that action be considered to reduce exposure then you will have an opportunity to reduce that exposure using the Graded Decision Guidelines and Company support. Any actions taken to reduce an exposure may be useful information to any prospective buyer. In some situations actions may enhance the value of your property.

Comment: Clarify the relationship between EPA, the Companies, and IT Corporation on this issue.

Response: EPA has signed an agreement with FMC and Monsanto to conduct the exposure study and implement the graded decision guidelines. IT Corporation was employed by the Companies to provide technical support. IT has now been replaced by Auxier and Associates of Knoxville, TN.

Comment: How long will the testing program be offered?

Response: EPA received many comments on the length of time the testing program should be offered ranging from a limited time offering to indefinite. Based on this input EPA and the Companies have agreed to conduct an initial phase of testing for approximately two years. During the initial phase there will be active promotion of the program to get as many homes screened as possible and complete an inventory of all public areas. After this initial phase the testing will be available for an indefinite period of time for those individuals that would like
to participate. The extended offer will be particularly useful to either new residents or individuals that would like to have a residence re-tested.

Comment: Will my testing results be confidential?

Response: Yes. The results of any testing will be maintained as confidential by the contractor working for the Companies and the District Health Department. Testing results will be reported to EPA and the public in aggregate only (no names and addresses will be used). For example, we might occasionally provide statistics on how many properties have been tested and what the range of results were.

Comment: What happens if either I don't participate in the program or only partially participate?

Response: Nothing! The testing is entirely voluntary and an individual can decide not to participate at any time.

Comment: Can radiation from phosphorus slag have any impact on anything else in my house, such as stored foods in a basement?

Response: No. Radiation levels from phosphorus slag are low enough to not have any direct or measurable impacts on anything else in the home.

Comment: What is the "Inventory" and how will it be used?

Response: The inventory is a listing or map of locations that have been tested and what the results were.

The SAB recommended that EPA formally record the location of slag to assure that the radioactivity due to slag content is adequately considered when disposing of the materials when these areas are eventually replaced (due to normal wear and tear). Information on the surveys of public areas will be part of the inventory. Individuals may also elect to have their home test results included on the inventory. This may be particularly true for homeowners whose test results were negative either at the time of initial screening or after taking actions to reduce exposures, or for those that have elected the "attrition" option.

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