UNEXPECTED RATES OF CHROMOSOMAL INSTABILITIES AND ALTERATIONS OF HORMONE LEVELS IN NAMIBIAN URANIUM MINERS

A common problem in determining the health consequences of radiation e xposure is factoring out other carcinogenic influences. The conditions in Namibia provide a test case for distinguishing the effects of long -term low-dose exposure to uranium from the other environmental factor s because of good air quality and the lack of other industries with ne gative health effects. Present records indicate a much higher prevalen ce of cancer among male workers in the open-pit uranium mine in Namibi a compared with the general population. The objective of the present s tudy was to determine whether long-term exposure to low doses of urani um increases the risk of a biological radiation damage which would lea d to malignant diseases and to derive a dose-response model for these miners. To investigate this risk, we measured uranium excretion in uri ne, neutrophil counts and the serum level of FSH, LH and testosterone and analyzed chromosome aberrations in whole blood cells using fluores cence in situ hybridization. A representative cohort of 75 non-smoking , HIV-negative miners was compared to a control group of 31 individual s with no occupational history in mining. A sixfold increase in uraniu m excretion among the miners compared to the controls was recorded (P < 0.001). Furthermore, we determined a significant reduction in testos terone levels (P < 0.008) and neutrophil count (P < 0.004) in miners c ompared to the unexposed controls. A threefold increase in chromosome aberrations in the miners compared to the nonexposed controls was reco rded (P < 0.0001). Most remarkably, cells with multiple aberrations su ch as ''rogue'' cells were observed for the first time in miners; thes e cells had previously been found only after shortterm high-dose radia tion exposure, e.g. from the Hiroshima atomic bomb or the Chernobyl ac cident. We conclude that the miners exposed to uranium are at an incre ased risk to acquire various degrees of genetic damage, and that the d amage may be associated with an increased risk for malignant transform ation. As expected, the chronic radiation injury of the hematopoietic system resulted in low neutrophil counts. Also, low hormone levels pro bably reflect damage to the gonadal endocrine system, (C) 1997 by Radi ation Research Society.