Neurological and neurophysiological examinations of workers exposed to arsenic levels exceeding hygiene standards

Department of Occupational Diseases and Toxicology, Nofer Institute of Occupational Medicine, Łódź, Poland
Department of Toxicology and Carcinogenesis, Nofer Institute of Occupational Medicine, Łódź, Poland
Institute of Sociology, University of Lodz, Łódź, Poland
Int J Occup Med Environ Health 2014;27(6):1013–1025
Objectives: The assessment of the neurotoxic effect of arsenic (As) and its inorganic compounds is still the subject of interest due to a growing As application in a large array of technologies and the need to constantly verify the principles of prevention and technological parameters. The aim of this study was to determine the status of the nervous system (NS) in workers exposed to As at concentrations exceeding hygiene standards (Threshold Limit Values (TLV) – 10 μg/m3, Biological Exposure Index (BEI) – 35 μg/l) and to analyze the relationship between the NS functional state, species of As in urine and As levels in the workplace air. Material and Methods: The study group comprised 21 men (mean age: 47.43±7.59) employed in a copper smelting factory (mean duration of employment: 22.29±11.09). The control group comprised 16 men, matched by age and work shifts. Arsenic levels in the workplace air (As-A) ranged from 0.7 to 92.3 μg/m3; (M = 25.18±28.83). The concentration of total arsenic in urine (Astot-U) ranged from 17.35 to 434.68 μg/l (M = 86.82±86.6). Results: Syndrome of peripheral nervous system (PNS) was manifested by extremity fatigue (28.6%), extremity pain (33.3%) and paresthesia in the lower extremities (33.3%), as well as by neuropathy-type mini-symptoms (23.8%). Electroneurographic (ENeG) tests of peroneal nerves showed significantly decreased response amplitude with normal values of motor conduction velocity (MCV). Stimulation of sural nerves revealed a significantly slowed sensory conduction velocity (SCV) and decreased sensory potential amplitude. Neurophysiological parameters and the results of biological and environmental monitoring showed a relationship between Astot, AsIII (trivalent arsenic), the sum of iAs (AsIII+AsV (pentavalent arsenic))+MMA (monomethylarsonic acid) concentration in urine and As levels in the air. Conclusions: The results of the study demonstrate that occupational exposure to inorganic arsenic levels exceeding hygiene standards (TLV, BEI) generates disorders typical of peripheral neuropathy.