[Aplastic anemia and occupational factors in Japanese industries]

Four mail questionnaire surveys were conducted on the incidence of aplastic anemia among industrial workers throughout Japan in collaboration with industrial doctors during a period from 1970 to 1983. The following major results were obtained. 1. Response rates were 55.5% (874/1,574 enterprises) in the first mail questionnaire survey in 1970-1972, 65.3% (294/450) in the second survey in 1973, 49.1% (170/346) in the third survey in 1976-1980, and 76.6% (242/316) in the fourth survey in 1981-1983. There was no significant difference in industrial types among the four surveys. 2. The numbers of aplastic anemia patients newly diagnosed were 145 (112 males/33 females) in the first survey, 21 (16/5) in the second survey, 51 (41/10) in the third survey and 30(24/6) in the fourth survey. Incidence rates per million were 14.7 (14.4 males/15.5 females) in the first and second survey, 14.2 (13.5/18.3) in the third survey and 9.1 (8.6/11.9) in the fourth survey. The rates were almost constant from 1970 through 1980, but the rates decreased thereafter. The rate was higher in females than in males, but the difference was not significant. 3. Incidence rates were high in rubber industry (26.8 per million), paper industry (24.8), and petroleum industry (22.5), but there was no industrial type demonstrating a constantly higher incidence in every survey. Manufacturing industries showed a higher incidence (14.6) than nonmanufacturing industries (11.7). 4. By type of work, non-productive work (67.2%), i.e., clerical (30.8%), administrative (8.9%), technical (7.7%), were the main jobs of 247 registered aplastic anemia patients (193 males and 54 females). 5. Thirty patients had been exposed to noxious agents such as organic solvents (21 cases including 3 exposed to benzene), metals (6), and radiation (1). However, in these cases no causal relationship between exposure and disease onset could be demonstrated. 6. Thirty-nine cases had a drug-intake history before onset of the disease. Drugs given included chloramphenicol (4 cases), other antibiotics (4), antituberculosis agents (8), analgesics (6), and tranquillers (4). The results obtained revealed no positive evidence that occupational factors peculiar to Japanese industries were involved in triggering aplastic anemia.