History and Current Status of Dioxin Pollution in the Tama River (1990s to 2020s)

History and Current Status of Dioxin Pollution in the Tama River (1990s to 2020s)

1990s: Discovery of Contamination During the 1990s, highly toxic dioxin contamination was confirmed throughout the entire Tama River, drawing significant attention as an environmental issue. Investigations by the National Institute of Health Sciences (Ministry of Health and Welfare) detected the most toxic dioxin, "2,3,7,8-tetrachlorodibenzo-p-dioxin," at levels of 0.05 to 2.8 picograms per gram in bottom sediments, with concentrations found to be higher in the lower reaches of the river. The primary sources of contamination were identified as industrial wastewater and bleaching processes in the upper reaches, and waste incineration plants in Kawasaki City and the Ota Ward area of Tokyo in the lower reaches. Concerns arose about impacts on the river ecosystem and residents. Local residents and environmental groups formed the "Tama River Protection Association" and launched a cleanup campaign.

2010s: Efforts Toward Improvement During the 2010s, technological improvements at waste incineration facilities and strengthened regulations on industrial wastewater discharge were implemented to address the pollution problem. During this period, the average dioxin concentration in Tama River sediment decreased to 10 picograms TEQ/g, though high concentrations exceeding 50 picograms TEQ/g were still detected in some areas. Incineration facilities in Kawasaki City and Tokyo's Ota Ward introduced flue gas treatment technology, reducing dioxin emissions. Additionally, regular cleanup activities by local residents and NPOs contributed to improving the Tama River's environment. During this period, improving recycling rates also gained attention. Tokyo Metropolitan Government and Kawasaki City strengthened separate collection of waste plastics. This further reduced dioxin generation from waste.

2020s: Further Progress Entering the 2020s, environmental improvements in the Tama River continued. According to surveys by the Tokyo Metropolitan Government's Bureau of Environment, the average dioxin concentration in water in fiscal year 2020 was 0.18 picograms TEQ/L, and in sediment it was 6.5 picograms TEQ/g, representing a significant decrease compared to the past. However, some high-concentration detection points remain an issue.

Kawasaki City and Tokyo's Ota Ward introduced the latest exhaust gas treatment technology, reducing Tokyo's total dioxin emissions to approximately 5 grams TEQ per year. Efficient combustion technology using alternative fuels from Tomakomai also contributed. Furthermore, the Tokyo Tama Regional Resource Recycling Association continues investigations at the Futatsuzuka Disposal Site. Companies like Sumitomo Chemical and Sumitomo Mitsui Construction are developing alternative technologies for chlorinated compounds, demonstrating collaborative efforts between businesses and local governments to advance environmental conservation. Summary: Tama River Purification and Challenges The dioxin contamination discovered in the Tama River in the 1990s is showing signs of improvement after three decades of dedicated efforts. Through the introduction of the latest technologies, strengthened legal regulations, and active resident participation, the river environment has gradually recovered.
However, improving some high-concentration sites in the sediment and implementing sustainable water quality management efforts remain critical challenges. The Tama River case has become a notable model for water environment improvement across Japan.