Staff writerA team of scientists in Tokyo announced last weekend that it has found eggs in the spermaries of three out of 20 male flounder caught in the sea near the Kanto region.The scientists said the abnormality may have been caused by suspected endocrine disrupters, chemicals believed to disrupt the functions of reproductive hormones.The report on flatfish followed the discovery last year of a male carp with extremely small testes in Tokyo’s Tama River. Other reports have shown that deformities in sex organs have been found in snails caught in the Sea of Japan.Scientists stress the need for further research to determine the causes of these deformities and the possible effect of endocrine disrupters on humans. These findings have caused fear in society, partly because the causes are unclear and partly because the problem relates to the reproductive function of animals and maintenance of species.In June, experts in several fields, chemists, doctors as well as scientists specializing in birds, fish and amphibia formed an academic society to research endocrine disrupters. “What is happening to fish, birds and snails may be different in terms of their mechanisms, but the change seen in these animals may be the same at the root,” said Tsuguyoshi Suzuki, an expert on human ecology. “Tackling the issue of endocrine disrupters requires participation of experts from many related fields.”Suzuki heads the new society, which also includes researchers from corporations. Membership has reached 600 in the three months since it was formed. “The aim of this academic society is to help ensure public health by bringing experts from a wide range of fields together to discuss and exchange information about the issue,” said Suzuki, a professor emeritus at the University of Tokyo.The Environment Agency has listed 67 chemicals, including dioxin, dichloro-diphenyl-trichloroethane (DDT) and polychlorobiphenyl (PCB), as suspected endocrine disrupters.Scientists must thoroughly study the characteristics of the chemicals, such as how they could affect the endocrine system, which produces hormones needed for reproduction and other bodily functions, Suzuki said.On the other hand, the scientists must monitor wildlife and research the effects on humans, he said.To meet this second goal, cooperation with the public is essential, he said, adding that to understand these developments in nature, researchers need to organize a network with people such as fishermen.For research on humans, a system is needed that supports long-term study focusing on the public, he said.Implying there may have been an effect on humans, a Danish team reported that for unknown reasons, the average number of human sperm in semen has decreased during the past 50 years.But experts have not studied the causes in an organized manner, Suzuki said.”Researchers are having heated arguments on whether the number of human sperm is decreasing, and few have tried to find the cause under the assumption that it is decreasing,” he said.Although it may be necessary to determine whether this is indeed happening, researchers should start investigating the cause of the possible decline in sperm counts, Suzuki said.”It is a very serious situation if it is happening,” he said. “And research (on the cause) will take about 20 years to complete.”Suzuki was involved in research on mercury poisoning at an electrical manufacturing factory in the 1960s.While urging the factory to stop using mercury in its manufacturing process, he kept checking the health of workers for several years.”In that case, it took 10 years to solve the problem,” he said.Industries, for their part, must be willing to divulge information about the chemicals they emit, he said.Promotion of the Pollutant Release and Transfer Registers system, which obliges businesses to disclose the volume of their chemical-substance emissions, is important to understand and address issues involving endocrine disrupters, he said.”We haven’t known much about the suspected endocrine disrupters, and that is why both researchers and companies have to provide citizens with accurate information,” he said, adding that hopefully, the academic community will promote further understanding of the matter.

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