Neurobehavioural effects of occupational exposure to cadmium: a cross sectional epidemiological study

Background-A patient with unexplained minor behavioural changes associated with an axonal sensorimotor polyneuropathy had a history of chronic occupat ional exposure to cadmium (Cd). Although animal studies have shown that Cd is a potent neurotoxicant, Little is known about its toxicity for the human central nervous system. The aim of this study was to investigate the toxic potential of chronic occupational exposure to Cd on neurobehavioural funct ions. Methods-A cross sectional epidemiological study was conducted in a group of Cd workers and an age matched control group. Eighty nine adult men (42 exp osed to Cd and 47 control workers) were given a blinded standardised examin ation that consisted of computer assisted neurobehavioural tests (neurobeha vioural examination system), a validated questionnaire to assess neurotoxic complaints (neurotoxicity symptom checklist-60, NSC-60), and a standardise d self administered questionnaire to detect complaints consistent with peri pheral neuropathy and dysfunction of the autonomic nervous system. Historic al and current data on biomonitoring of exposure to Cd, either the highest value of Cd in urine (CdU in mu g Cd/g creatinine) of each Cd worker during work (CdUmax) or the current value (CdU-(current)) of each control, were a vailable as well as data on microproteinuria. Results-Cd workers (CdUmax: mean (range), 12.6 (0.4-38.4)) performed worse than the controls (CdUcurrent: mean (range), 0.7 (0.1-2.0)) on visuomotor t asks, symbol digit substitution (p=0.008), and simple reaction time to dire ction (p=0.058) or location (p=0.042) of a stimulus. In multiple Linear reg ression analysis, symbol digit substitution, simple direction reaction time test, and simple location reaction time test were significantly related to CdUmax, (beta=0.35 (p<0.001), beta= 0.25 (p=0.012), and beta=0.23 (p=0.021 ) respectively). More complaints consistent with peripheral neuropathy (p=0 .004), complaints about equilibrium (p=0.015), and complaints about concent ration ability (p=0.053) were found in the group exposed to Cd than in the control group, and these variables correlated positively with CdUmax (perip heral neuropathy: beta=0.38, p<0.001; equilibrium: beta=0.22, p=0.057; conc entration ability: beta=0.27, p=0.020). Conclusion-Slowing of visuomotor functioning on neurobehavioural testing an d increase in complaints consistent with peripheral neuropathy, complaints about equilibrium, and complaints about concentration ability were dose dep endently associated with CdU. Age, exposure to other neurotoxicants, or sta tus of renal function could not explain these findings. The present study a lso indicates that an excess of complaints may be detected in Cd workers be fore signs of microproteinuria induced by Cd occur.