Summary and Recommendations
Contamination of vast areas of land and huge amounts of water with dangerous long-lived radioactive and non-radioactive pollutants has posed a difficult problem for the generations of people who have created them. How can we ensure the health of future generations, of land and water resources, and of ecosystems thousands of years into the future?
The scientific tools at hand are relatively rudimentary, of recent vintage, and rife with uncertainties. The costs of cleanup of contaminated areas as well as their management, notably at the sites where processing of large amounts of nuclear materials has been done, are estimated to run into the hundreds of billions of dollars in the United States alone. Ensuring the effectiveness of public expenditures in ways that are compatible with health and environmental protection for thousands of years is a daunting task.
The nature of the problem requires the utmost care in the selection of the scientific tools that will be used to assess the health of future generations both in order to ensure a sound result and to promote effective expenditures. We have reviewed various approaches to protecting the health of people from radiation both in the present as well as in the long-term from the point of view of scientific defensibility. The scientific merits of any approach must take into account the historical experience that institutional memory about contamination is prone to fade in decades even in circumstances where very dangerous materials like chemical weapons have been handled and dumped. Laws can and do change, as do norms. Assessment of the risks of particular materials and of combinations of materials has evolved. Over the decades, the trend in official studies and evaluations has been to see radioactivity as more dangerous per unit of exposure than initially believed. In general, standards for environmental protection have become more stringent and support for such protection has increased.
Standard setting processes must take these fundamental considerations into account. A failure to do so is to risk the long-term health of both people and the environment.
Principal finding
Our principal finding is that the "subsistence farmer scenario," which assumes that people will live on the land and eat locally grown food, is a scientifically sound basis on which to base cleanup standards in general and regulations for residual radioactivity in the soil in particular. This finding is independent of any interim uses for which specific sites, such as the plutonium-contaminated Rocky Flats site near Denver, may be designated. It is not appropriate to assume that site control, institutional memory, and legal land use restrictions will prevail for hundreds of years, to say nothing of thousands of years. There is little factual basis for such assumptions and much evidence that they are unwarranted.
Choosing residual soil action levels based on the assumption that a wildlife refuge designation will endure for generations could result in residual radioactivity levels as high as several hundred picocuries of plutonium per gram of soil. This would be an unprecedented backward step in the history of the cleanup program.
Principal recommendation
Our principal recommendation for the Rocky Flats site is that, even if the site is designated as a wildlife refuge, the standard for residual radioactivity in the soil should be set assuming that at some time in the future the site will be used by a resident farmer or rancher.
One can derive a range of residual radioactivity levels for plutonium (and associated americium-241) based on the subsistence farmer approach, depending on details about groundwater use and future evolution of regulations in relation to groundwater. Current safe drinking water rules of the EPA for plutonium, americium, and other transuranic radionuclides have been set based on four-decade-old data, ignoring more recent data and calculation methods. They are also at variance with the State of Colorado limits for plutonium content of surface water, which are 100 times more stringent than current federal safe drinking water provisions for transuranic radionuclides. Drinking water rules for transuranics that are compatible with the Colorado rule for surface water or with the federal rule for most beta emitters would result in stringent residual soil levels toward the lower end of the range we recommend to be considered.
IEER recommends that residual soil action levels between 1 and 10 picocuries per gram be considered as the basis for the cleanup program at Rocky Flats, whether or not the site is designated as a wildlife refuge. This range is consistent with the approach we recommend. Soil action levels deriving from scenarios related to designation of the site as a wildlife refuge should be rejected.
There is official precedent for choosing a residual soil action level in this range. The preliminary recommendation for a remediation goal for industrial use of the Department of Energy's Lawrence Livermore National Laboratory site is 10 picocuries of residual plutonium per gram of soil. For a residential use scenario, the goal would be 2.5 picocuries per gram.
Other findings
- The concept of the hypothetical maximally exposed individual has been the basis for protecting the general population from radiation released by nuclear facilities.
The hypothetical maximally exposed individual is a person at the site boundary who would receive the highest dose from a facility's operations. This is a hypothetical person in that it does not necessarily correspond to any actual person. The basis is that if the exposure of this hypothetical person is less than the maximum allowable then the rest of the population is also protected. Unlike radiation workers, the general population does not have radiation measuring equipment or monitoring, and this necessitates a conservative and more statistical approach to radiation protection that will ensure the health of the population to a high degree. An extension of this idea in time provides a part of the scientific basis for a subsistence farmer approach to protecting future generations.
- The concept of the subsistence farmer scenario has evolved as the long-term equivalent of the hypothetical maximally exposed individual in situations where contamination or waste disposal activities may put future generations at risk.
Many radionuclides as well as other pollutants are very long-lived. Their fate in the environment over such long periods is very difficult to estimate with a high degree of precision. Long-term uncertainties are great on many fronts. Lifestyles, diet, population settlement patterns, land-use regulations, climate, environmental protection standards, future assessments of the risk of pollution or contamination, and future utility of specific resources are among the important factors that contribute to these uncertainties. The choice of a framework for cleanup cannot resolve these uncertainties as to what will happen, but it can address them in a manner as to make the cleanup standards relatively robust to changes that might occur.
The subsistence farmer scenario provides a reasonable, scientifically and historically defensible framework that is robust to a large variety of future uncertainties. Local use of land and water for farming and consumption is well founded. It is conservative in that there are few assumptions about future lifestyles that will result in much greater exposures. The remaining uncertainties are then in the parameters chosen for modeling future doses, such as those related to climate and hydrology and those related to mobility of contaminants through the environment. These can be addressed with reasonable conservatism in the subsistence farmer framework.
- The wildlife refuge scenario does not provide an adequate basis for long-term public health protection.
The designation of a site such as Rocky Flats as a wildlife refuge does not address the many fundamental issues raised by the uncertainties as regards changing land-use, changing laws, lack of institutional memory, that are among the issues that are at the heart of the use of the subsistence farmer scenario as the method of choice for long-term population protection. The phasing of cleanup and issues related to keeping people out of a contaminated site should not be confused with the central concerns that give subsistence farmer scenario a robust character as the sound scientific choice for setting cleanup standards.
- It is not clear that the integrity of wildlife will be protected over the long-term even if the designation of the site as a refuge can be sustained indefinitely.
Emerging understanding of genome-ecosystem interactions have led to the postulation of a genetic "uncertainty principle" according to which induced genetic changes that do not produce observable deleterious effects in individuals of a species may nonetheless be harmful to the entire species over the long-term. Understanding of genome-ecosystem interactions at the molecular level is still rudimentary at best. Radiation is one of the causes of genetic mutation. Some random mutations are harmful. It is therefore not at all clear that a designation of a contaminated site as a wildlife refuge will be protective of the integrity of species over the long-term even if it there is no observable harm to individual wildlife specimens in the short-term.
Other recommendations
- The designation of Rocky Flats as a wildlife refuge should not serve as a precedent for other sites or for reducing cleanup expenditures at other major DOE nuclear weapons sites.
- The Department of Energy should adopt the subsistence farmer scenario as the basis for the cleanup program throughout its nuclear weapons complex.
There is a considerable amount of literature supporting the idea of wildlife refuges at the major DOE weapons sites. The use of this designation as a way of avoiding cleanup expenditures would not be protective of future generations. While it is not desirable to release contaminated areas to the public, and site restrictions of various types may be adopted to achieve this goal in the short-term, that should not become the basis for avoiding the use of the subsistence farmer scenario as the basis for cleanup goals and standards.
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Institute for Energy and Environmental Research