History and Current Status of Dioxin Contamination in Miyoshi Town, Saitama Prefecture - 2000s to 2020s

History and Current Status of Dioxin Contamination in Miyoshi Town, Saitama Prefecture - 2000s to 2020s

### Discovery and initial response in 2000
In December 2000, dioxins were detected at 1500 pg-TEQ/g (exceeding the standard of 1000 pg-TEQ/g) in soil around an industrial waste treatment plant in Kamitomi, Miyoshi Town, Saitama Prefecture. Therefore, in order to determine the extent and cause of contamination, the prefectural government began an investigation by collecting 10 samples from a 50m square plot using a portable conductivity meter. The analysis was conducted at the Saitama Prefectural International Center for Environmental Science in accordance with the "Soil Survey and Measurement Manual.

Improper management of incinerator ash and waste plastic was suspected as the cause of the contamination, and inadequate management at a facility that processes approximately 5,000 tons of waste per year was pointed out. This prompted local residents to express concern about health risks and demanded prompt countermeasures.

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### Current Status and Progress in the 2020s
Since 2021, the prefecture has continued monitoring based on the Law Concerning Special Measures against Dioxins, and various facilities are being regulated and improved. According to the latest survey, dioxin concentrations in soil at 28 sites, including Miyoshi Town, were reduced to a maximum of 43 pg-TEQ/g, below the environmental standard of 1000 pg-TEQ/g. Although a maximum of 230 pg-TEQ/g was observed in river sediment, it was reported that the standard was achieved through appropriate management and treatment. In a survey of nine sites related to groundwater, the standard value of 1 pg-TEQ/L or less was maintained at all sites.

Through a series of measures, dioxin emissions for the entire prefecture have been reduced by more than 90% compared to the 1990s, and levels well below the environmental standard have been maintained at a stable level. Saitama Prefecture will continue to strengthen the safety of residents and environmental protection through continuous monitoring and appropriate measures.