Electrophysiological assessment in paint workers with chronic exposure to organic solvents

ABSTRACT

Exposure to organic solvents has been associated with many neurological deficits. However, not all solvents are equally neurotoxic. The association of clinically significant polyneuropathy with long term occupational exposure to organic solvents, alone or in combination, is controversial. The aim of this study was to assess the effects of chronic occupational exposure to a mixture of certain organic solvents upon the peripheral nervous system [PNS] in exposed painting workers and detection of sub-clinical affection. The population of this cross-sectional study included two groups. The exposed group comprised 40 male workers recruited from a paint factory. Twenty male workers, age matched, with no contact with the exposure environment, from the same factory were eligible as a control group. The exposed workers were further divided into two groups group [I] and group [II] according to frequency and the pattern of usage of personal protective equipment [PPE]. The materials frequently used in painting process were included; epoxy, calcium carbonate, barium sulfate, n-butanol, titanium dioxide, xylene and zinc oxide. All workers were subjected to a structured interview questionnaire about their exposure and medical history as well as complete general and neurological examinations. Bilateral nerve conduction studies [NCSs] for motor [common peroneal, median and ulnar] nerves and sensory [sural, median and ulnar] nerves were performed for all the study population using a standardized protocol. The diagnosis and classification of neuropathy was established using a combination of symptoms, signs, and NC measures consistent with standard clinical practice. Potential confounders of NC measures were examined. Mean values for nerve conduction velocities [NCVs] for all studied motor and sensory nerves were highly significantly slower in exposed workers compared to control group [p<0.01]. The same results were recorded for the mean values for SNAP amplitudes. Regarding motor nerves CMAP amplitudes, there was significant difference only for tibial nerve. There was no significant difference of distal latencies for any estimated nerve either sensory or motor. For whole exposed group [n=40], 19 workers [47.5%] had at least one abnormal NC measure in two or more of evaluated nerves; 11 workers [27.5%] fulfilled criteria for confirmed clinical neuropathy whereas 8 workers [20%] fulfilled the criteria for sub-clinical neuropathy. The results NCSs of exposed workers with regular and complete protection [group I], exposed workers with partial protection [group II] and controls demonstrated significant differences regarding all parameters of all studied nerves except sensory latency of ulnar sensory nerve and motor amplitudes of median motor and tibial motor nerve. Regarding the inter-group comparisons, there were significant differences between the three groups for all SNCVs and only the MNCV of tibial nerve [p<0.01]. Other evaluated parameters of both motor and sensory nerves were affected with different significant degrees except distal latency of ulnar sensory nerve and motor amplitudes of median motor and tibial motor nerves[p>0.05]. The median sensory nerve was the only nerve which showed highly significant differences between the 3 groups regarding all its evaluated parameters [p<0.05]. Also only ulnar motor nerve showed highly significant differences between workers of group I and workers in group II regarding its all evaluated parameters of [p<0.05]. In the studied population [n=60], exposure, age and smoking were found to have significant effects on some NC measurements on logistic regression analysis. In the exposed group [n=40] using of PPE, type of job [regarding the spray painters] and duration of exposure, in years, had significant effects on certain NC parameters based on the same model of logistic regression analysis. Chronic exposure to the mentioned organic solvents was associated with solvent induced toxic polyneuropathy [SITP] as proved by the results of abnormal electrophysiological parameters of the evaluated peripheral nerves for all exposed workers group. Appropriate medical strategies to reduce such morbidity as periodic medical evaluation and electrophysiological assessment should be implemented