Abstract
The increased potential for tritium releases from either nuclear reactors or from new facilities raises questions about the appropriateness of the current ICRP and WHO recommendations for tritium exposures to human populations. To study the potential toxicity of tritium as a function of dose, including at a regulatory level, mice were chronically exposed to tritium in drinking water at one of three concentrations, 10 kBq.l−1, 1 MBq.l−1 or 20 MBq.l−1. Tritium was administered as either HTO or as tritiated non-essential amino acids (TAA). After one month’s exposure, a dose-dependent decrease in red blood cells (RBC) and iron deprivation was seen in all TAA exposed groups, but not in the HTO exposed groups. After eight months of exposure this RBC decrease was compensated by an increase in mean globular volume - suggesting the occurrence of an iron deficit-associated anemia. The analysis of hematopoiesis, of red blood cell retention in the spleen and of iron metabolism in the liver, the kidneys and the intestine suggested that the iron deficit was due to a decrease in iron absorption from the intestine. In contrast, mice exposed to external gamma irradiation at equivalent dose rates did not show any change in red blood cell numbers, white blood cell numbers or in the plasma iron concentration. These results showed that health effects only appeared following chronic exposure to concentrations of tritium above regulatory levels and the effects seen were dependent upon the speciation of tritium.
Highlights
Environmental and human health effects, especially through water contamination, have the potential to be caused by these releases
Two different forms of tritium were used, HTO and organically-bound tritium (OBT) (in the form of a mixture of three amino acids (AA), alanine, glycine and proline). These amino acids were chosen for several reasons: They are highly soluble in water so the exposure is easy to manage by their addition to drinking water[27,28]; They are non-essential amino acids that participate in normal AA metabolic processes; They are frequent in vertebrate proteins[29]; With the exception of proline, they are non-functional AA, i.e. not implicated into key metabolic pathways[30]
This 4% to 6% decrease in red blood cells (RBC) number compared to the control values was associated with decreased hemoglobin concentration, decreased hematocrit and decreased mean corpuscular content in hemoglobin in the 1 and 20 MBq.l−1 exposure groups (Fig. 2B–D). These changes were not observed in the HTO groups, except for a slight increase in MGV in the 20 MBq.l−1 exposure group. This result indicates the presence of a dose-dependent decrease in RBC in animals exposed to tritiated non-essential amino acids (TAA) but not in those exposed to HTO
Summary
Environmental and human health effects, especially through water contamination, have the potential to be caused by these releases. Current tritium regulations are most commonly based on the recommendations of the International Commission on Radiological Protection (ICRP) and of the World Health Organization (WHO) which recommend limits on the annual exposure from radionuclides in drinking water to 0.1 mSv2. To fill the knowledge gap, a large-scale in vivo mouse study was conducted to study the biokinetics and non-cancerous/carcinogenic effects of tritium incorporation at low concentrations relevant to possible human exposures and current regulations. Details about this large-scale study have been published[26]. A detailed analysis of hematologic parameters is presented and the link between observed tritium-induced changes and modifications in iron metabolism are investigated
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
