The Environment Agency said Friday it will put priority on studying four chemicals believed to disrupt the endocrine systems of humans and wildlife after a survey found them in concentrations that could affect living organisms.

Roughly 50 chemical substances were detected and classified into five groups in the nation’s first comprehensive survey of contamination levels in the environment, the agency said in a report released Friday.

Of these, four — tributyltin, nonylphenol, octylphenol, and di-n-butyl phthalate — were found in some areas in concentrations that may have an impact on life, and were tagged as “A substances,” deserving priority risk assessment.

The study covered 61 of 67 chemical substances targeted by the government in May 1998 as possible endocrine disrupters, and its results have highlighted how pervasive the chemicals are, agency officials said.

Endocrine disrupting chemicals are synthetic substances believed to impair the reproductive and mental development of animals, as well as their immune systems and sexual functions.

The report was submitted the same day to a review committee appointed to address the topic.

The six chemical substances not covered in the report have either been studied separately — such as dioxin — or have not been produced in Japan and are unlikely to be found in the environment, according to agency officials.

The survey tested for contamination levels in water, air, soil, sediment and animals at 2,430 sites around the nation. All but 11 of the 61 chemicals targeted were detected in at least one medium surveyed.

The highest levels of chemicals were found in wildlife. Twelve species, including fish, birds, amphibians and mammals — both aquatic and land based — were studied.

“Dolphins, whales and birds of prey all showed high levels (of chemical contamination),” said Shinsuke Tanabe, a marine environment expert and a member of the review committee, indicating that the highest levels of contamination were generally found in species at or near the top of the food chain.

The survey also found abnormalities in the sex organs of a male carp and a male raccoon dog. However, no connections with contamination levels in the animals could be confirmed.

The next step for the agency is a risk assessment of the chemicals, which will begin before the end of the year at the earliest, officials said.

The classification system used in the report is based on how pervasive the chemical is, whether its usage is increasing, and whether or not it has been shown to disrupt the endocrine system.

Since this is the first national study on endocrine disrupting chemicals and there is a dearth of literature both at home and abroad on their contamination and its effects, it is difficult to determine what the levels in the report mean, agency officials acknowledged.

But the study does give the government a foundation for analyzing the threat of each suspected disrupter.

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