Animal Studies of Residual Hematopoietic and Immune System Injury From Low Dose/Low Dose Rate Radiation and Heavy Metals [open pdf - 178KB]
It is clear that there is an adaptive response to low dose rate exposures. However, as the authors of this report describe, recovery of marrow precursor cells after a second exposure may be incomplete. This could be due to any combination of factors such as persistent deficiency of stem cells, accelerated cell cycling of marrow precursors leading to increased ratios of S-phase populations among stem cells, shortened lifespans of immature erythroid and myeloid cells, and others. Part of the problem in studying the effects of damage repair after low dose exposures is that the damage is minimal, and detection of changes accordingly is difficult. More research needs to be carried out in this field. One unique feature of this report is the combination of radiation effects with those from the heavy metals cadmium and lead. These metals, both marrow-toxic and immunotoxic in their own right, affect the outcomes of radiation exposures even at low doses and low dose rates. Particularly in situations involving radiation contamination from occupational accidents or environmental releases, one may expect to seldom encounter victims adversely affected by radiation alone. A host of other physicochemical agents, ranging from metals such as these to solvents and other substances, are likely to be present. The authors' findings regarding the additive and/or synergistic effects of simultaneous or nearly simultaneous exposure to radiation and toxic metals are important for this reason. We trust that readers of this work will find their approach and findings stimulating and useful for their own understanding and efforts.
AFRRI Contract Report 98-3; DNA 001-96-C-0047