Body burden of aluminum in relation to central nervous system function among metal inert-gas welders

Objectives The relationship between elevated internal aluminum loads and ce ntral nervous system function was studied among aluminum welders, and the t hreshold level for adverse effect was defined. Methods For 65 aluminum welders and 25 current mild steel welders body burd en was estimated, and the aluminum concentrations in serum (S-AI) and urine (U-AI) were analyzed with graphite furnace atomic absorption spectrometry with Zeeman background correction. Referents and low-exposure and high-expo sure groups were defined according to an aggregated measure of aluminum bod y burden, the group median S-Al levels being 0.08, 0.14, and 0.46 mu mol/l, respectively, and the corresponding values for U-Al being 0.4, 1.8, and 7. 1 mu mol/l. Central nervous system functions were assessed with a neuropsyc hological test battery, symptom and mood questionnaires, a visual and quant itative analysis of electroencephalography (EEG), and P3 event-related pote ntials with pitch and duration paradigms. Results Subjective symptoms showed exposure-related increases in fatigue, m ild depression, and memory and concentration problems. Neuropsychological t esting revealed a circumscribed effect of aluminum, mainly in tasks demandi ng complex attention and the processing of information in the working memor y system and in the analysis and recall of abstract visual patterns. The vi sual EEG analysis revealed pathological findings only for aluminum welders. Mild, diffuse abnormalities were found in 17% of the low-exposure group an d 27% of the high-exposure group, and mild to moderate epileptiform abnorma lities at a frequency of 7% and 17%, respectively. Conclusions Both objective neurophysiological and neuropsychological measur es and subjective symptomatology indicated mild but unequivocal findings do se-dependently associated with increased aluminum body burden. The study in dicates that the body burden threshold for adverse effect approximates an U -Al value of 4-6 mu mol/l and an S-Al value of 0.25-0.35 mu mol/l among alu minum welders.