Nippon Eiseigaku Zasshi (Japanese Journal of Hygiene)
Online ISSN : 1882-6482
Print ISSN : 0021-5082
ISSN-L : 0021-5082
Epidemiological Studies on the Morinaga Powdered Milk Poisoning Incident
Masahiko OhiraHideyasu Aoyama
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1972 Volume 27 Issue 6 Pages 500-531


In 1955, many babies who had drunk arsenic-tainted milk produced at the Tokushima Plant of the Morinaga Milk-Industry Company Ltd., suffered from serious poisoning. The number of victims ascertained in February, 1956 covering 27 prefectures in the western part of Japan was 12, 159, of whom 131 died.
The disaster was caused by the process of manufacturing the powdered milk. Disodium phosphate was added as a stabilizer to make the milk easily soluble. This disodium phosphate was poorly purified, intended for non-food industrial use, and contained a toxic dose of arsenic, sodium arsenite and vanadium compounds etc.
Shortly after the disaster, numerous medical reports were published. A committee organized by the Society for Child Health (the chairman was Prof. Nishizawa of Osaka University; so it was called the Nishizawa Committee), determined criteria for the diagnosis of the poisoning; but these criteria were inadequate and erroneous from several points of view. Strange to say, debates and publications about the disaster disappeared quickly after the report was published by the Health Department of Okayama Prefecture stating that the victims had recovered completely according to the criteria established by the Nishizawa Committee only one year after the disaster.
Until 1969, when Prof. Maruyama et al., of Osaka University reported on victims whom they had visited, no study had been made to ascertain whether or not there were any after-effects of the poisoning. Much fault must be found with the Ministry of Health and Welfare, with the attitude of the Morinaga Company, and with the doctors concerned, for this neglect to follow-up such an unprecedented and large-scale disaster.
In 1969, the authors managed to organize an epidemiological study group with several departments of Hiroshima University and the Department of Hygiene of Okayama University cooperating and have developed joint research on this disaster as follows:
1. A follow-up survey was made among victims in Okayama Prefecture between December 1969 and April 1970. 214 people answered the questionnaire and 74 were given a medical examination.
2. A prospective study was made on the basis of a questionnaire on clnical complaints collected at the time of the disaster in 1955.
3. A comparative study was performed between the victims and their brothers and sisters.
4. A comparative study was performed among handicapped children in institutions in Okayama Prefecture, who were born between January 1st, 1953 and December 31st, 1955. The children were divided into three groups, namely those who had consumed the arsenic-tainted milk, those who were brought up on different brands of powdered milk from different companies, and those fed only maternal milk.
5. A comparative study was performed among all children born between January 1st, 1954 and December 31st, 1955 and brought up in Seno district in Hiroshima Prefecture which has a relatively stationary population and where good records had been kept of the physical growth and mental development of the children in the nursery, primary and junior high schools. The children were divided into the same three groups as mentioned above. This study was performed as a joint research project by the Departments of Public Health (Director: Prof. M. Tanaka), Orthopedics (Director: Prof. K. Tsuge), Ophthalmology (Director: Prof. T. Dodo) and Psychiatry and Neurology (Director: Prof. K. Sarai) of Hiroshima University Medical School and Deparment of Conservative Dentistry (Director: Prof. T. Inoue) of Hiroshima University Dental School, and Department of Hygiene (Director: Prof. M. Ohira) of Okayama University Medical School. All clinical examinations were conducted separately under the double blind method.
6. The 124 cases of the children examined in the district of Senogawa town were discussed individually by the six medical doctors and five dentists who did the examinations.

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