Elsevier

Environmental Research

Volume 87, Issue 2, October 2001, Pages 92-98
Environmental Research

Regular Article
Declining Minamata Male Birth Ratio Associated with Increased Male Fetal Death Due to Heavy Methylmercury Pollution

https://doi.org/10.1006/enrs.2001.4293Get rights and content

Abstract

The purpose of this retrospective study was to examine the effect of methylmercury pollution on the sex ratio of offspring at birth and of fetuses at stillbirth in Minamata City, Japan, in the 1950s when severe and widespread methylmercury pollution was experienced. In 4 of 5 years from 1955 to 1959 when methylmercury pollution was most severe, lower numbers of male offspring at birth were observed in the city population. The offspring sex distributions from 1950 to 1969 by 5-year period were calculated in the overall population of Minamata City, in the most prevalent area, in fishermen (most heavily exposed occupation group) and among Minamata disease patients using data from birth certificates. We also similarly calculated the sex ratio of stillborn fetuses in the city population using Kumamoto Prefecture's vital statistics on still-birth. Decreases in male births were observed in offspring in the overall city population, in fishermen, and in maternal Minamata disease patients in the city in 1955–1959, when the methylmercury pollution was most severe. An increase in the proportion of male stillborn fetuses in the city was observed at the time. It is possible that male fetuses were more susceptible to the pollution than their female counterparts, and this could be a cause for the lower numbers of male offspring at birth.

References (13)

There are more references available in the full text version of this article.

Cited by (0)

Part of this work was supported by a grant for Encouragement of Basic Research at the National Research Institute from the Science and Technology Agency, Japan. Birth certificates were made available by the District Legal Affairs Bureau strictly for research purposes under the condition of nondisclosure.

2

Address correspondence and reprint requests to Mineshi Sakamoto, Ph.D., Department of Epidemiology, National Institute for Minamata Disease, 4058-18 Hama, Minamata City, Kumamoto 867-0008, Japan. Fax: +81-96661-1145. E-mail: [email protected].

View full text