Airborne dioxin levels were comparatively low last year, according to an Environmental Agency survey, but further research is necessary to more accurately determine how the toxin affected air pollution, officials said upon releasing the results Thursday.

The agency conducted the survey in the last summer and winter at 10 places across the country, such as metropolitan areas and residential zones near industrial areas.

The average density of dioxin in each of the 10 areas surveyed fell between 0.095 and 0.32 picograms per cu. meter. All the average figures were below 0.8 picograms, the standard level set under the agency’s guidelines established last year, officials said.

A picogram is one-trillionth of 1 gram. The highest density of the toxin — 0.54 picograms per cu. meter — was found in the winter at Tokyo’s Shinjuku Ward, the survey shows.

Compared with the 1996 survey, the average density of dioxin declined at each area, but the officials said they did not think this was attributable to recent awareness of the issue, or measures that have been taken to curb the emission of dioxin. “This survey showed comparatively low levels of dioxin in the air, maybe because it was conducted just twice and only at the 10 locations,” said Takashi Iijima, the agency’s air pollution control division chief, adding that the budget for the survey was not sufficient to conduct a full-scale investigation.

But this year, the survey will be extended to about 400 locations, and may bring different results, he said.

Along with the sense of urgency in the need to assess the negative effects of dioxin on humans, which include deformities and cancer, the agency was able to obtain 4.74 billion yen for dioxin-related work in 1998 as compared with just 60 million yen in 1997.

“We know of many preventive measures that can be taken,” he said. Dioxin is emitted when vinyl chloride is incinerated at a low temperature.

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