NOSE, Osaka Prefecture--The highest concentrations of carcinogenic dioxins in the nation have been found in sludge in a pond at a municipal garbage incinerator plant in this northern Osaka community, officials in charge of the plant's operation said Thursday.
The results of dioxin samplings taken since November 1997, when initial survey results were released, showed dioxin concentrations of 23,000 picograms per gram of topsoil in the pond sludge at a site 100 meters from the smokestack of the garbage incinerator.
Toxic substances are usually reported in terms of parts per million, but dioxins are deadly hybrid compounds, emissions often resulting from low-temperature burning of materials that are themselves harmful, and the concentrations are so dangerous that their presence is measured in picograms--trillionths of a gram.
Representatives of a local agricultural cooperative expressed shocked concern over the results of the survey. Although there is no evidence plants grown in dioxin-contaminated soil absorb the pollutants themselves, sales of vegetables grown in the area had just begun to recover after having dropped sharply after the presence of dioxins was first reported in November.
Dioxins are very toxic, and are linked to cancer and other health problems. The Ministry of Health reports that in Germany, the government restricts agricultural use of land if more than 40 picograms of dioxin are detected in 1-gram soil samples, and children are advised not to play on land where more than 100 picograms of dioxin are found in soil samples.
The incinerator in Nose, built 10 years ago, has not been used since June 1997. That was when officials found airborne dioxin emissions that were well beyond the Health Ministry's safety standards.
In November, officials sent experts to conduct a series of studies of dioxin concentrations in soil and water nearby after readings of 2,700 picograms were detected in a chestnut grove on the grounds of a local high school. In November, the readings showed the highest dioxin concentrations ever found in the nation up to that time.
The latest findings were based on samples taken at 48 sites in a 5-kilometer area south of the incinerator, the officials said. They found 8,500 picograms of dioxin in soil samples right next to the incinerator stack. Soil samples from 12 other points found 1,000 picograms or more.