Dioxin concentrations up to 16 times above national safety guidelines were detected in soil in Tokyo’s Ota Ward, making it the nation’s second-worst dioxin contamination in a public place, Tokyo metropolitan government officials revealed Wednesday.

The dioxin — a suspected endocrine disrupter — was found in soil underneath a paved municipal road in an industrialized area of the ward, located in southern Tokyo, earlier this year.

At one point surveyed, 16,000 picograms of dioxin per gram of soil was detected. The government’s accepted limit for dioxin in soil is 1,000 picograms per gram. A picogram is one-trillionth of a gram.

Officials said there was no immediate concern for the health of the nearby community, since the contaminated soil was located under the asphalt pavement and there were less than 10 people residing nearby.

“However, it would be very dangerous if the soil is exposed to the surface,” one official said.

The Tokyo government said it would conduct further inspections of the site in question and begin deliberations on how to dispose of the contaminated soil.

Officials said it was the second-highest dioxin concentration in soil detected in Japan where the affected area is open to the public. The highest concentration — in which 36,000 picograms of dioxin were detected in soil — was found in the city of Hashimoto, Wakayama Prefecture.

Other high-profile dioxin contamination cases have mostly been in areas off-limits to the general public, such as incinerators and their surrounding areas.

The contamination came to light after the metro sewage authorities dug up the area in February and found “oily soil,” which was later collected for analysis.

Ota Ward sent it off for further analysis after polychlorinated biphenyls (PCBs) were detected in the first test conducted in March.

The result of the second analysis came out in mid-July and revealed a high concentration of coplanar PCBs.

This substance has a chemical structure similar to dioxin and is treated as a dioxin under the revised law governing dioxin.

The metro government officials said they believe the carcinogen was dumped at the site before the road was paved over in the late 1950s.

Around that time, there was a chemical plant nearby, and the site was later turned into a storage yard.

The officials said there was a strong possibility the site was used to store condensers and voltage transformers containing PCBs, which used to be widely used in and heat conductors before being banned.

Wednesday’s announcement came almost two months after the initial discovery of the dioxin. During this time, the issue went back and forth between the metro government and the ward, apparently because of a dispute regarding who should take the initiative in dealing with the problem.

The metro officials said they received the report from the ward after the result of the second analysis came out but asked the ward to conduct another test to obtain a more precise report before making the findings public.

However, the ward told the metro government to take care of the case in late August despite the latter’s repeated call for another test, according to Tokyo officials.

Ota Ward officials, meanwhile, said Wednesday that once the dioxin was detected, another analysis would not alter the facts of that discovery. They asked the metro government, which is legally the responsible entity, to take the initiative in conducting the research to avoid overlapping operations.

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