AUTONOMIC FUNCTION IN MANGANESE ALLOY WORKERS

The observation of orthostatic hypotension in an index case of mangane se toxicity lead to this prospective attempt to evaluate cardiovascula r autonomic function and cognitive and emotional neurotoxicity in eigh t manganese alloy welders and machinists. The subjects consisted of a convenience sample consisting of an index case of manganese dementia, his four co-workers in a ''frog shop'' for gouging, welding, and grind ing repair of high manganese railway track and a convenience sample of three mild steel welders with lesser manganese exposure also referred because of cognitive or autonomic symptoms. Frog shop air manganese s amples 9.6-10 years before and 1.2-3.4 years after the diagnosis of th e index case exceeded 1.0 mg/m(3) in 29% and 0.2 mg/m(3) in 62%. Twent y-four-hour electrocardiographic (Holter) monitoring was used to deter mine the temporal variability of the heartrate (RR' interval) and the rates of change at low frequency (0.04-0.15Hz) and high frequency (0.1 5-0.40Hz). MMPI and MCMI personality assessment and shortterm memory, figure copy, controlled oral word association, and symbol digit tests were used. The five frog shop workers had abnormal sympathovagal balan ce with decreased high frequency variability (increased In LF/ln HF). Seven of the eight workers had symptoms of autonomic dysfunction and s ignificantly decreased heart rate variability (rMSSD) but these did no t distinguish the relative exposure. Mood or affect was disturbed in a ll with associated changes in short-term memory and attention in four of the subjects. There were no significant correlations with serum or urine manganese. Power spectrum analysis of 24-h ambulatory ECG indica ting a decrease in parasympathetic high frequency activation of heart rate variability may provide a sensitive index of central autonomic dy sfunction reflecting increased exposure to manganese, although the con tribution of exposures to solvents and other metals cannot be excluded . Neurotoxicity due to the gouging, melding, and grinding of mild stee l and high manganese alloys (11-25%) merits air manganese and neuropsy chologic surveillance including autonomic function by Holter monitorin g of cardiovagal activation. (C) 1998 Academic Press.