USING PSYCHOLOGICAL-TESTS FOR THE EARLY DETECTION OF NEUROTOXIC EFFECTS OF LOW-LEVEL MANGANESE EXPOSURE

The neurotoxic effects from chronic exposure to high concentrations of manganese dust are well known from studies of highly exposed miners, as well as from numerous clinical reports. The very first of these rep orts dates back to the early 19th century (Couper, 1837). A thorough r eview of the toxicity of manganese was provided by the WHO in 1981 (WH O, 1981). If is evident from these early reports that the critical eff ect from manganese exposure, i.e. the effect used in the establishment of environmental exposure criteria, is the effect on the central nerv ous system (CNS). Furthermore, impaired motor functions are clearly ce ntral to the manganese syndrome (WHO, 1981). It is also obvious from t he clinical knowledge gathered over the years, that once the neurotoxi c effects from manganese exposure are openly manifested at the clinica l level, the damage to the CNS is essentially irreversible, and may, i n some cases, be progressive. For this reason, detection of early sign s of Mn exposure is fundamental to the prevention of chronic neurotoxi c illness in manganese exposed populations. Very few investigations ha ve been studying early signs of manganese toxicity by the use of behav ioural methods in groups of active workers before the onset of clinica lly observable problems. To our knowledge, there are only four studies reported using behavioural measures to explore possible CNS effects f rom current industrial levels of manganese exposure in asymptomatic po pulations (Siegl and Bergert, 1982; Roels et al., 1987; Iregren, 1990; Roels et al., 1992). This short review will treat the results from th ese four published papers, together with some data from a recent study at the Universite de Quebec, Montreal (Mergler et al., 1994) and the preliminary outcome from a study performed at the Institute of Occupat ional Health, University of Brescia, Italy (Lucchini et al., in press) . The paper also provides a discussion of some aspects that may make a test of motor function sensitive to the effects from manganese exposu re, and, finally, presents a recommendation for a core set of tests th at may be efficient to use while testing for the early neurotoxic effe cts from low level manganese exposure. (C) 1994 Intox Press, Inc.