When elemental phosphorus is produced, it is removed from a mixture of phosphate ore, silica, and coke. The largest remaining by-product is a lava-like rock known as "slag". Primarily a compound of calcium and silica, slag also contains small quantities of uranium and radium these two elements are naturally present in the phosphate ore. Their presence in the slag causes it to emit very low levels of gamma radiation - a type of radiation similar to medical x-rays.
Residents throughout Southeast Idaho are invited to participate in a voluntary program conducted jointly by Southeastern Idaho Public Health, FMC, Monsanto, and EPA. The program helps residents find out if phosphorus slag in their homes and business properties is causing unacceptably high exposure to radiation. In the past, slag has been used in roofs, basement foundations, sidewalks and driveways.
High doses of radiation can be harmful or even fatal. The damage caused by exposure to radiation is determined by the type of radiation, the duration of exposure, and the part of the body that is exposed. The effects of a radiation dose are either prompt or delayed. Prompt effects occur within the first several months after exposure. Delayed effects occur over many years. The delayed effects can include cancer or other diseases in exposed persons and harmful effects on unborn children.
It is important to note that an average of one in four people develops some form of cancer. Excess lifetime cancer risks resulting from exposure to radiation are calculated in addition to this number. Risk estimates assume that even small amounts of radiation pose some risk.
The total number of observed cancers in Southeast Idaho is low by national standards. Healthy lifestyles, rural living, and a low incidence of smoking and drinking likely contribute to the lower overall incidence of cancer in this area. Despite low cancer rates in the region, however, EPA remains concerned about possible increases in cancer risk that may be associated with slag. For that reason, EPA, Monsanto, and FMC are hopeful that area residents will participate in the phosphorus slag program.
In 1992, FMC, Monsanto, and the U.S. EPA jointed together to form the Phosphorus Slag Technical Work Group. The Technical Work Group was convened to develop guidelines to help individuals interpret radiation exposure results from the phosphorus slag program and determine what, if any, action should be taken to reduce their exposure.
The Technical Work Group is composed of two Monsanto and FMC representatives; two EPA representatives; two company-selected and two EPA-selected radiation experts; and one representative each from the City of Pocatello, the City of Soda Springs, the State of Idaho, and the Shoshone-Bannock Tribes.
The Phosphorus Slag Technical Work Group has developed a set of guidelines to help residents make decisions based on the results of the program. The Technical Work Group's recommendations include a range of things that can be done to reduce residents' exposure to radiation from slag. They include: attrition, or removing the slag once the structure's useful life has ended; alterations in how the occupants use the area; and building additional living space to replace areas that contribute to elevated radiation doses.
The Phosphorus Slag Technical Work Group recommends the following action options for reducing individual radiation dose. The options start with the easiest and least expensive and range up to the most difficult and costly. It is the TWG's view that simpler and easier options are more appropriate for lower doses while more costly options would be more appropriate at higher doses.
Scientific opinion differs on how much low-level radiation and individual can be exposed to without harm. The possibility exists that there may be a threshold level of radiation exposure below which there are no adverse health effects. Consequently, exposure to natural background radiation levels may not pose any health risks. However, current evidence suggests that exposure to radiation at very low levels may pose some risk of cancer.
Education and counseling would include a balanced discussion of radiation risk and radiation protection measures. This would include exploring the range of possible actions that could be taken to reduce and individual's dose, such as possible changes in use patterns - like spending less time in the basement.
Attrition means removing slag once a structures' useful life has ended. This would involve listing the building on the phosphorus slag inventory and subsequent removal of the slag to an appropriate disposal location when the building is demolished.
Space that contributed to radiation dose would be converted to an alternative use in order to reduce the amount of time that individuals spend in that space.
This option involves reducing exposure by making physical changes to the building either through removal or shielding of the slag areas.
This option would provide additional living space to replace areas that contribute to an elevated dose. For example, a new bedroom could be built onto a home to replace a basement bedroom.
The Phosphorus Slag Technical Work Group anticipates that cost-effective risk reduction options will be considered on a case-by-case basis, and each homeowner will have an opportunity to discuss any specific concerns with a radiation risk professional.
Residents in Southeast Idaho may experience elevated radiation doses in their homes and business properties from many sources. The primary focus of the phosphorus slag program is on gamma radiation from phosphorus slag that has been used as a building material in many area buildings. Some buildings may have elevated radon levels which increase radiation dose to the occupants. Radon is an invisible, odorless gas and a natural part of the environment. It will be important to know the level of radiation resulting from radon in addition to that resulting from phosphorus slag so that appropriate measures can be taken to protect the residents' health. Because of this, property owners participating in the program may also have their buildings surveyed for radon.
Dr. Tom Gesell
Professor of Physics and Astronomy
Idaho State University
Pocatello, Idaho 83209
Traci Lambson, MHE
Phosphorus Slag Program Coordinator
Southeastern Idaho Public Health
1901 Alvin Ricken Drive
Pocatello, Idaho 83201