n-ヘキサン取扱者に発生した多発性神経炎の原因の追求とその症例について

(1) 17 cases of intoxication polyneuritis occurred in 17 workers exposed to n-hexane vapour in recent years, from 1960 to 1962, in Japan. (2) 6 cases of those occurred in 3 small polyethylene laminating plants. In these plans, in the first process, gravure printed cellophane sheet was smeared with n-hexane solution containing 5% organic titan, tetra isopropyl titan or tetra buthyl titan. Solvent n-hexane was vapourized with warm air and n-hexane vapour contaminated the air of the workroom. Organic titan, remained on the printed surfarce of cellophane sheet, was rapidly hydrolized with water in the air to titan oxide. In the second process, fused polyethylene was painted thinly on this surface. Titan oxide on this surface accelerated adhesion of polyethylene with cellophane, and cellophane sheet was laminated fast with polyethylene. This laminated sheet had the character of clear printed colour and water-proof, and was used widely as packing materials of foods, confectionery and others. Concentration of n-hexane vapour in the air around the machine in the first process was 1000∼2500 ppm. N-hexane used in these plants contained impurties, i.e. methyl pentane (16%) methyl cyclopentane (20%). Titan was not detected in the air. Working time was 10∼12 hours and workers became drausy in half or one hour and went outdoor to inspire fresh air for 10 to 15 minutes. (3) 11 cases of those occurred in a great pharmaceutical plant. In this plant, 95% n-hexane was used as a remover of grease on the surface of tablets. Tablets in wire netting were immersed for 5 minutes in n-hexane within the immersion box, and tablets in wire netting were dried on the shelf. N-hexane vapourized from the surface of the tablets and the immersion box. Concentration of n-hexane vapour was 1000 ppm around the immersion box and 500 ppm at the center of the workroom. Workers stayed in this room for 8 hours except for the noon recess. (4) In all cases symptoms of intoxican began with the same subjective complaints. The first complaint was fatigue in all cases and loss of appetite in some cases, followed by paresthesia in distal parts of the extremities, weakness, and difficulty in walking. Symptoms and signs advanced during the exposure and this progress was arrested finally three months after removing from the exposure, and the symptoms gradually improved throughout the period between six and thiry months. This characteristic process of development and improvement of symptoms was not such as usually seen in common polyneuritis. All diagnosis of these cases by clinical and hygienic examinations was intoxication polyneuritis of the mixed form. (5) In the first case, n-hexane, impurities in n-hexane and organic titan were suspected of the causes of intoxication. But in the second case, the cause was only n-hexane. N-hexane causes undoubtedly intoxication polyneuritis in man. One of my co-workers, Miyagaki proved experimentally the occurrence of intoxication neuritis due to n-hexane in rats. (6) Till now, n-hexane was regarded as of lowtoxic solvent owing to its low toxicity on the hematopoiesis and the liver function. But the present result showed that toxicity of n-hexane on the peripheral neuron was not insignificant.