Neurologic dysfunction from exposure to 2-t-butylazo-2-hydroxy-5-methylhexane (BHMH): a new occupational neuropathy.

Seven cases of subacute central and peripheral neurologic dysfunction developed in 18 workers employed in the manufacture of reinforced plastic bathtubs. Cases were characterized by weight loss, dizziness, paresthesias, muscle weakness, incontinence, memory loss, and loss of peripheral, color, and night vision. Neuropathies began distally, involved both sensory and motor function, and were associated with prolonged sensory latency, muscle fibrillation, and reduced numbers of functioning motor units. One patient developed posterior lenticular cataracts. Slow improvement occurred on removal from exposure, but residual neuropathies persisted for as long as two years. Epidemiologic investigation disclosed that the first case developed approximately two weeks after introduction of a new plastic foaming agent, 2-t-butylazo-2-hydroxy-5-methylhexane (BHMH). All cases occurred in workers exposed directly to BHMH. No new cases developed after use of BHMH was discontinued. A survey of the firm which produced BHMH and of 68 user firms found two additional clusters of mild neuropathy which may have been caused by BHMH. BHMH was withdrawn from distribution following discovery of these cases. Subsequently, BHMH has been shown in rats to be a potent neurotoxin. Adequate premarket testing could have averted this outbreak.