Toxic neuropathies

Peripheral neuropathies induced by inorganic lead compounds and the organic solvents n-hexane and methyl-n-butyl-ketone have been well described and predominantly affect motor nerves, but mercury and polychlorinated biphenyls cause a predominantly sensory neuropathy. Regeneration usually follows slowly and uneventfully provided exposure is halted in affected employees. It would be inadvisable for any employee with a pre-existing neuropathy of any aetiology to be exposed knowingly to such an additional hazard, regardless of the standard safety precautions in the workplace.

Heavy metal toxicity and organic solvents

An acute encephalopathy associated with exposure to aluminium was first described in smelter workers. It was known as ‘pot room palsy’, and characterized by incoordination, poor memory, and impaired abstract reasoning.20 Permanent neuropsychological impairment has been reported following occupational exposure to high doses of metals such as mercury, arsenic, zinc, and manganese, either by inhalation or after accidental ingestion.

More controversial is whether low-level chronic exposures to metals, either in the workplace or the environment, could be responsible for cognitive dysfunction and dementia. The literature includes various papers assessing neuropsychological function in workers at risk. In some studies, researchers have assessed subclinical endpoints, such as workers having non-specific symptoms or no symptoms. It remains uncertain whether continued occupational exposure may lead to clinical and irreversible problems.22

This is also true of organic solvents that are widely used in manufacturing industry, dry-cleaning, degreasing, and paint production and application. The acute effects of organic solvents range from mild fatigue to frank psychosis. The weight of evidence suggests that chronic exposure to hydrocarbon solvents at current limits does not appear to cause adverse neurobehavioural effects. Nevertheless, there is still controversy over the severity of effects that can arise from workplace exposure. Psychosis, dementia, and compensatable disability appear to be more frequent in Scandinavian studies, but less severe effects have been described in other Western countries.23,24

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