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THE EFFECT OF UNDERGROUND NATURAL CHRONIC EXPOSURE OF FEMALE WISTAR RATS IN URANIUM MINE TO HIGH LEVEL OF RADON-222 PROGENY

Stela Râmboiu (1) , E. Bordas (1) , Adriana Olinic (2)
(1) Institute of Public Health, 6, L. Pasteur Street, 3400 Cluj–Napoca, Romania
(2) University of Medicine and Pharmacy, Histology Department, 6, L. Pasteur Street, 3400 Cluj–Napoca, Romania

The effect on fertility of chronic exposure of female Wistar rats in “Avram Iancu” uranium mine to
high Radon-222 and Radon-222 progeny concentrations in air was investigated. Time variations of
fertility index as well as the histological aspect of ovaries were analysed. The experiments were
performed on adult Wistar rats (females) exposed for 52 days to high Radon-222 (28,749 Bq.m -3 ) and
Radon-222 progeny levels in the underground air. The cumulated exposure of exposed rats was of
20.26 WLM. Two female control groups (underground and laboratory) were used. For both control
groups Radon-222 level in the air was of about 78 Bq.m -3 . As regard the external gamma dose there
were not significant differences between the exposed and control groups. Each group was divided into
three subgroups. The exposed rats were cross-mated with controls, five days after the end of the
exposure (subgroup one) and six and ten months later (subgroup two and three, respectively). The
fertility index was compared with that obtained for control groups. Immediately after mating the
females were sacrificed and the ovaries were weighted and then embedded in paraffin and stained
with hematoxilin-eosin. Histological aspect was analysed. Immediately after the exposure there were
no differences between fertility index for exposed and control groups. Six months later the fertility
indices for cross-mated group with control groups was zero. Ten months after the end of the exposure
the fertility index remained zero. For both unexposed groups the fertility index do not changed in
time. The weight of ovaries/100 g body weight for exposed group decreased in time. For the control
groups no variation were found. Histology showed normal morphology in the ovaries of exposed rats
immediately after the end of the exposure. The aspect does not differ for exposed and control groups.
The chronic exposure of female Wistar rats to high level of Radon-222 and Radon-222 progeny lead
to a significant alteration of the histological aspect of ovaries ten months after the end of the exposure.
In controls the histological aspect of ovaries did not changed in time. These results suggest that the
exposure of animals to Radon-222 progeny is related not only to high incidence of lung cancer, but
also to sterility induction. The observed effect had a long latency period and could not be related to
external gamma dose, which was too small to produce the observed effect.
Key words: fertility, Radon-222 progeny exposure