Distribution of Species on Sandy Substrates

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EXHIBIT 33

Low-Level Radiation Effects from Nuclear Fission Products in the Environment

E.J. Sternglass

Department of Radiology

School of Medicine

University of Pittsburgh

Pittsburgh, Pennsylvania 15213

May 5, 1970

In the difficult problem of establishing radiation standards at low doses and low dose-rates such as occur in normal peace-time operations of nuclear plants or from the testing of nuclear weapons, the principal problem has always been to find a way of clearly establishing the risk to health at radiation levels approaching those of normal background radiation.

Without definite quantitative knowledge of these risks for large human populations, it is impossible to arrive at a meaningful evaluation of the ratio of benefit to risk needed in arriving at decisions affecting the health of those exposed to radiation as compared with the benefits of an economic or aesthetic nature to be derived from the use of nuclear energy, or to make a meaningful comparison with the health effects of alternative means of meeting society's needs for energy.

Until now, the estimates of risk from low-level radiation to man when protracted over many weeks, months or years have been based on measurements carried out either at high doses or at high dose-rates, so that the calculation of expected effects at low doses and doserates always contained a large element of uncertainty. The estimates of risk therefore required the assumption that one could predict the effects at low doses and protracted exposures by means of a straightline extrapolation from effects observed at high doses, implying that there was essentially no recovery or reduced risk of cancer and genetic damage when the dose was spread out.

However, in many animal studies and even in man, some degree

of recovery has been observed after the administration of high doses of radiation in certain biological effects, so that although linearity

between dose and effect has generally been assumed to hold in the setting of radiation standards, it could not be proved for the protracted doses from fallout or natural radiation.

There were also other important sources of uncertainty in the setting of standards for permissible radiation levels to the general population. One of the major ones arose from the fact that human experience with radiation had been mainly obtained from a study of adult workers in occupations involving radiation. But it is known from innumerable laboratory studies on animals that it is not the mature animal that is most sensitive to radiation, but the developing young animal, and especially the early fetus in the initial period of cell differentiation and organ formation.

A second source of uncertainty has been the fact that most studies of radiation effects on the large numbers of animals, needed to observe the more subtle effects, involved the use of externally produced x-rays or gamma-rays rather than radiation from ingested or inhaled radioisotopes. The reason for this is that it is much easier to control the rate of radiation and the amount administered by means of external sources of radiation that can readily be turned on and off.

However, the situation for which one wishes to obtain an estimate of health effects as a result of nuclear fallout or reactor operation and possible accidents involves not only external gamma radiation from a passing cloud of radioactive debris or activity on the ground, but radiation produced by nuclear fission products taken into the body through the air, the food and the water. Although the actual radiation emitted from these radioactive particles is in many cases similar to