Press Release

Table of Contents

Acknowledgements

Summary and Recommendations

1. Introduction

2. The concept of the critical group and the maximally exposed individual

3. Description of the subsistence farmer scenario

4. International use of the subsistence farmer approach

5. Reasonableness of the subsistence farmer scenario on occupational grounds

6. Relation of the subsistence farmer scenario to Radionuclide Soil Action Levels (RSALs) at Rocky Flats

7. Erosion of the subsistence farmer scenario

8. The Radioactive Wildlife Refuge

9. Enforcement for the eons

10. Conclusions and Recommendations

11. References

Short-term considerations such as availability of funds or priorities such as plutonium stabilization (as is the case at Rocky Flats) cannot detract from the reality that long-term site control is unrealistic and should not be the basis for cleanup plans. A failure to set stringent standards can result in increased risks to an unknowing and unsuspecting public in the future. This would not be the case were public health protection under a reasonably strict criterion undertaken from the very beginning.

The problem of leaving sites with huge amounts of contamination has recently been dramatically illustrated in the capital of the United States in relation to abandoned chemical munitions in one of the most sought-after real estate locations in Washington, D.C. - the area near American University.

In 1986, the United States Army discovered that there were abandoned chemical munitions on the grounds of American University and parts of the environs of the campus, including some homes. The horribly confusing situation that has emerged in the course of just one century in a plush area of the capital of the country should, perhaps suffice to dispel any illusions regarding long-term site control, the vigilance of the authorities or even their use of common sense in informing people at risk. The following is based on an article in the Washington Post on July 25, 2001. There have been many news articles, official reports, and other documents around this problem in the past fifteen years.

The Army did not inform local authorities in 1986 when it found the problem. A pair of reports in 1995 by the Army, which had investigated its own conduct in 1986, came to the following confusing conclusions:

One of the serious problems arising from the Army's chemical dumping in the area has been high arsenic contamination of the soil, including the yards of many homes. In one such case, the high contamination was discovered in 1994 but officials covered up the discovery of the contamination, presumably for fear of the potential liabilities, even though it was high enough to designate the soil as hazardous waste. In the meantime the family that lived in the home used the garden, planted things. Children played in it. One of the people (the mother) got a brain tumor that was operated on, but there is now no way to tell whether it was caused by the arsenic. The family will live in fear that their children may develop diseases as a result of their exposure for the rest of their lives. This occurred despite the family's vigilance, since they did ask the authorities repeatedly whether they would face problems as a result of the contamination. The family was not informed of the contamination until 1999, when they demanded all the documentation. They were reassured by the government that all would be well, and no action was taken, despite the high levels of arsenic. In 2001, the family moved out of the house.

When the official purpose of an operation has been fulfilled and the funds have dried up, site control can be tenuous, and institutional memory even more so. The tendency to cover up even at possible cost to people's health is strong, and this is not the only case in which such tendencies can be seen. There are, after all, no designated funds to deal with it. It is an old operation whose benefit to the sponsoring institution has long since expired.

Besides the evolution of conditions on a site and of site use that may increase the risk to future generations, there is also possible evolution of the understanding of risk per unit of exposure. Historically, radiation protection standards have been set in terms of radiation dose. There is a consideration of cancer risk in the process of setting standards, but a limitation on the risk itself has not generally been used in the standard setting process. The reason, of course, is that one can measure dose, in principle, while risk is a more abstract concept, even though it is the one most directly linked to population protection.

The issues in regard to whether risk or dose should be the measure in setting residual soil action levels (RSALs) is a complex one. For instance, it is likely that the stream of money available for clean up would dry up once the site has been taken off the books of the party that owns it. This makes it quite different from worker protection in an operating factory, for instance. Moreover, it is impossible to actually measure dose to future populations. Therefore, if the goal is to protect generations a considerable time into the future, then it is prudent to revisit the issue of risk versus dose as the basis for setting RSALs (as well as other cleanup standards).

There are several aspects to considering risk versus dose issues:

1. In general, risks depend on the organ exposed, age at exposure, and, for some kinds of cancer, gender.
2. It is important to consider non-cancer risks, and a simple dose approach often is not conducive to such assessment.
3. There may be synergistic effects between exposure to non-radioactive hazardous materials and radioactivity.
4. The same dose may result in a different risk to different sections of the population, since it is likely that sensitivity to radiation is highly variable in populations, even if they are otherwise homogeneous by age, class, ethnicity and gender.
5. The scientific evaluation of the risk of radiation may change with time, as it has in the past.
6. The regulatory procedure by which standards are established may change.

A risk approach to soil action levels could deal with each one of the factors specified in item A above (organ, age, and gender), while a dose approach usually considers a single cancer risk factor when setting the dose limit. A risk approach to residual soil action means that the implications of the proposed RSALs for various cancers (organ specific doses) and for different populations would need to be examined. The RSAL would be set only after the doses assessed in these different ways have been evaluated and their implications for cancer risk have been calculated. Dose assessments are all scenario-dependent. In general, the subsistence farmer or rancher (i.e., consuming local food and water only) scenario is the appropriate one to consider in evaluating risks.

There are a variety of non-cancer risks, some of which are radionuclide-dependent. The dose approach to regulation adds up all doses, internal as well as external, into a single effective dose equivalent and then applies a cancer risk factor. This approach does not give adequate weight to adverse outcomes, such as miscarriages due to intake of tritiated water or developmental risks to children and fetuses from other radionuclides, such as strontium-90, iodine-129, tritium, and cesium-137 which cross the placenta. While these particular radionuclides are not thought of as problems in the Rocky Flats environment, they have been present in the past. The main point here is that different radionuclides carry different risks.

A risk-based approach allows the differentiation of internal from external radiation and hence allows for better organ, gender, and age-specific evaluation of the consequences of cleanup rules. A recent study evaluating the risk of DNA aberrations in the children of Chernobyl liquidators found a surprising seven-fold increase compared to children of the same people born before the exposure of the parent.¹⁰² This high mutation rate is at considerable variance with the Hiroshima/Nagasaki data. The latter data indicate a doubling of mutations at doses of 100 to 200 rad. These are considered high doses of radiation, when delivered in a short time, as, in fact, they were by the bombings. By contrast, Chernobyl liquidator doses have been estimated to be in the low-dose range -- 5 to 20 rad. No dose reconstruction was possible for the specific persons in the study. Still, the clear conclusion of the study is that low dose radiation, possibly an order of magnitude or more less than the Hiroshima/Nagasaki doses cited above, could cause the same mutation rate.

The Chernobyl study did not attempt to assign a cause of the high mutation rate, other than to identify it with radiation dose. It is plausible that at least some of the difference from the Hiroshima/Nagasaki data may be due to internal exposure of the liquidators. The doses received by Hiroshima/Nagasaki survivors were mainly external gamma and neutron doses. The main concern at Rocky Flats would be the internal exposure from alpha radiation. An internal dose of an alpha emitter would be more harmful than an external one.

The large uncertainties in the area of heritable mutations can be factored in better using a risk-based approach. A safety factor that corresponds to the uncertainty arising from the fact that exposures to future populations from plutonium in the Rocky Flats environment will largely be internal can be developed using Chernobyl liquidator data from the above study, for instance.

Rocky Flats, like many other DOE sites, has both radioactive and non-radioactive pollution. Little is known about synergistic risks of toxic chemicals and radionuclides, particularly when considerations of internal dose discussed briefly above are taken into account. Chemicals may compromise immune and/or endocrine systems in ways that may increase risks from radionuclide intake. The scientific consideration of such issues is in its initial stages, and it would be a surprise if there were no surprises as regards synergistic health risks. A risk-based approach would include an evaluation of what is known, the extent of the ignorance about synergistic effects and the implications of that analysis for choosing a safety factor that would allow risks to be kept below specified levels. An approach that relies only on cancer risk deriving from radiation dose alone by its nature excludes these important considerations.

The occurrence of cancer appears to be mediated by the immune system. The immense variation in allergic response among populations that are relatively homogeneous in other respects implies that there may be a large differential sensitivity to radiation between individuals. A risk-based or a dosimetric approach to RSALs could take this into account, were the differential sensitivity known. Alternatively a safety factor that would reduce allowable dose or risk may be selected. In any case, it is prudent to explicitly factor in some consideration of possible differential population sensitivity to radiation within homogeneous population groups.

It is difficult to select a safety factor at the present time since the factors that contribute to differential allergic response are only now beginning to be understood. Typically, these factors are genetic, developmental, and environmental, making the situation quite complex.

A safety factor that acknowledges this ignorance is especially important in regard to long-lived residual radioactivity. The long half-lives mean that a variety of people are likely to come into contact with the residual radioactivity over the ages. There is therefore a high likelihood that individuals who are among the most sensitive in the population will at some time be exposed.

The past half-century has seen increases in estimates of cancer risk per unit of dose based mainly on reassessments of Hiroshima and Nagasaki survivors. Future assessments of these data may or may not result in increases in risk, depending on such factors as whether the missing cohorts from the time immediately after the explosions are taken into account and how neutron doses are evaluated and interpreted.

There are a number of differences between the populations that would be exposed to residual radioactivity and Hiroshima/Nagasaki survivors. The recent study of the children of Chernobyl liquidators creates additional uncertainty about too heavy a reliance on Hiroshima/Nagasaki data, though these should of course be included in risk evaluations. Reductions in cancer risk estimates for future populations exposed to residual radioactivity based on reassessments of Hiroshima/Nagasaki data would be especially inappropriate at this time. For a variety of reasons, many of which are discussed above, the uncertainties in regard to risk per unit of exposure to future populations are much greater than those indicated by the analysis of Hiroshima/Nagasaki survivor data.

Besides changes in regulations arising from changes in risk assessment, regulations may be changed due to other factors. Regulations generally result from a variety of historical, institutional, scientific, and political considerations. They can therefore have glaring inconsistencies that may be corrected at some future time when the political conditions are appropriate. Take, for instance, safe drinking water regulations in relation to transuranic radionuclides. These regulations allow total contamination by these radionuclides of up to 15 pCi per liter. At the same time, the doses for most beta emitters are limited to 4 mrem per year. The allowable concentrations are not specified but must be derived from prevalent dose conversion factors. It turns out that if the currently applicable dose conversion factors are applied to transuranics, the drinking water doses resulting from 15 pCi per liter would be roughly a hundred times greater than the 4 mrem allowed for most beta emitters. Contamination of water to just a fraction of a picocurie of plutonium-239/240 is sufficient to yield a drinking water dose of 4 mrem per year. It is quite possible that the public might demand both consistency and water purity in the future, given that the public places a very high value on water purity.

The State of Colorado already has a state standard for plutonium in surface water of 0.15 pCi/L and at Rocky Flats the standard is enforced at the downstream boundary of the site where 30-day moving average is calculated from streams exiting the site. For two separate 30-day periods in 1997, averages for Walnut Creek exceeded the standard.¹⁰³ Moreover, as noted above, the Colorado standard is a reasonable one based on the 4 mrem annual drinking water dose limit that applies to most beta emitters. There is no rational reason for that same limit not to be extended to alpha emitters.

The DOE has suggested changing the Colorado standard by changing the averaging period from one month to longer periods.¹⁰⁴ At the same time, a multi-year study concluded that cleanup to an RSAL of 10 pCi/g would not meet the 0.15 pCi/L water standard for the most contaminated areas downstream from the 903 Pad (the most contaminated part of the Rocky Flats facility).¹⁰⁵ This is one example of the uncertainty of regulatory issues.

Other changes may arise from the fact that there has been as yet no regulatory assessment, much less action, on possible synergisms between hormonally active compounds, like PCBs and dioxins, and radiation doses. Recent acceptance of the potential harm by hormonally active compounds for non-cancer end-points, such as developmental abnormalities, as well as advances in the biological effects of radiation at the cellular and sub-cellular level could lead to considerable changes in the regulatory system in the coming decade or two. It is not possible at this time to predict the magnitude of these changes, but some risk estimates may go up as these effects are considered for the simple reason that the present assumption is of zero synergisms in the absence of data and analysis.

Next: 10. Conclusions and Recommendations

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