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 reports dates back to the early 19th century (Couper, 1837). A thorough review of the toxicity of manganese was provided by the WHO in 1981 (WHO, 1981). It is evident from these early reports that the critical effect from manganese exposure, i.e. the effect used in the establishment of environmental exposure criteria, is the effect on the central nervous system (CNS). Furthermore, impaired motor functions are clearly central to the manganese syndrome (WHO, 1981). It is also obvious from the clinical knowledge gathered over the years, that once the neurotoxic effects from manganese exposure are openly manifested at the clinical level, the damage to the CNS is essentially irreversible, and may, in some cases, be progressive. For this reason, detection of early signs of Mn exposure is fundamental to the prevention of chronic neurotoxic illness in manganese exposed populations. Very few investigations have been studying early signs of manganese toxicity by the use of behavioural methods in groups of active workers before the onset of clinically observable problems. To our knowledge, there are only four studies reported using behavioural measures to explore possible CNS effects from current industrial levels of manganese exposure in asymptomatic populations (Siegl and Bergert, 1982; Roels et al., 1987; Iregren, 1990; Roels et al., 1992).(ABSTRACT TRUNCATED AT 250 WORDS)