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Contaminants found in Japanese macaques' fetal brain may hint at risk to humans: researchers

A screenshot of an article in the academic journal Environmental Science & Technology revealing the findings of the first discovery of PCB in a primate's fetal brain is shown here. (c) 2020 American Chemical Society

IMABARI, Ehime -- A group of researchers in western Japan has discovered chemical contaminants in the fetal brain of a Japanese macaque, which could apparently be used as information on contamination risks among humans.

    It is the first recorded case of this kind in the world, according to the team led by Kei Nomiyama, an associate professor at Ehime University's Center for Marine Environmental Studies. The team had initially announced their first finding during a 2014 academic debate of the Japan Society for Environmental Chemistry. Furthermore, an essay including additional specific analysis on the chemical's toxicity was recently published in the international academic journal Environmental Science & Technology.

    Although polychlorinated biphenyl (PCB), which was used as insulating oil in transformers and capacitor devices in the past, was banned from being manufactured and used in Japan in 1972, the compound is thought to currently remain in widespread areas in the environment. The team examined the placentas and amniotic fluid of nine pregnant primates, and the brains and livers of the fetuses. PCB and OH-PCB, which is made when PCB enters the body, were detected in all test samples.

    This Jan. 9, 2019 photo shows Kei Nomiyama, an associate professor at Ehime University, in the western Japan city of Matsuyama, Ehime Prefecture. (Mainichi/Nobuto Matsukura)

    High concentration levels of OH-PCB -- a wet weight of 22 to 32 picograms (one picogram is one trillionth of a gram) -- were detected in the brains of fetal macaques during the early to middle periods of pregnancy. This amount is said to be at "a level at which negative effects on neurodevelopment are feared."

    Similarly high concentration levels of 43 to 65 picograms of OH-PCB were detected in their livers. As fetuses in the latter stage of pregnancy were reported to have between 11 and 20 picograms of the compound, the team suspects that it was diluted following the fetus' growth.

    Associate professor Nomiyama commented, "It can be naturally thought that similar contamination is occurring in human embryos. Neurons are actively produced in human embryos between the early and middle stages of pregnancy, and considering that an active growth of the cerebral neocortex is also seen during this period, the research can be thought to produce basic information on the general evaluation of the risks of contaminants."

    For inquiries about the discovery, please contact Ehime University at

    (Japanese original by Nobuto Matsukura, Imabari Local Bureau)

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