The Shadow of Tokyo as Told by the Formation of Hexavalent Chromium: Memories of the City of Oshima, Koto-ku, Tokyo (1970s-1990s)

The Shadow of Tokyo as Told by the Formation of Hexavalent Chromium: Memories of the City of Oshima, Koto-ku, Tokyo (1970s-1990s)

The events surrounding hexavalent chromium pollution in Koto and Edogawa wards are not merely a case of pollution, but a story that quietly illuminates the reverse side of Tokyo's urban development from the postwar period to its period of rapid economic growth. In particular, the chemical sludge lying underground in Oshima, Koto-ku, symbolizes what the city of Tokyo had pretended not to see in order to grow, and the act of digging up the soil itself was like a process of confronting the city's unacknowledged desires and past inconveniences.

In the momentum of postwar reconstruction, Tokyo reorganized the west side of the city as residential areas and the east side as factory areas. In Koto and Edogawa wards, plating factories and chemical plants were concentrated, and waste liquids and sludge containing hexavalent chromium were poured into landfills and along canals without any established treatment methods. The city was simultaneously light and shadow, and the shadow sank underground. Neither the government nor the residents were fully aware of the dangers, and the land was quietly contaminated.

In 1970, the situation changed drastically with the Diet session on pollution. Yellowish soil, corroded oil drums, and hexavalent chromium detected at a proposed school site. The limitations of an era that refused to see the invisible were exposed, and the silent soil finally spoke out. The fact that a large amount of hexavalent chromium sludge was buried in an underground disposal site on Oshima came to light, but only after the area had already been transformed into a residential area and schools and parks had been built. The dangers that had been neglected behind the scenes of urban development were finally beginning to show themselves.

In the 1980s and 1990s, residents questioned the responsibility of the Tokyo Metropolitan Government and proceeded to litigation. The issues at stake were at what stage the government recognized the danger, the extent to which it was obligated to explain the situation to the residents, and whether the decision to develop the site was appropriate. While the Tokyo District Court ruled that there was insufficient proof to find that the Tokyo Metropolitan Government had clear intent or gross negligence, it harshly pointed out the seriousness of the contamination and the administration's lack of explanation. Beyond the victory or defeat, the weight of this decision lay in the fact that it made visible the structural problems facing the city.

Since the 1990s, the Tokyo Metropolitan Government has promoted decontamination work, digging up sludge, treating it with chemicals, and monitoring groundwater. However, complete removal of hexavalent chromium is not easy, as it can remain toxic for more than a hundred years if it sinks deep underground. The shadow of the former city still lurks in the land of Oshima, Koto-ku, and continues to quietly raise the question of how urban planning and environmental ethics should be linked.

The problem of hexavalent chromium contamination is not limited to the soil in Koto and Edogawa wards. It is also the city's long memory of how it prioritized profit and sacrificed everything in the course of its rapid economic growth, and how deeply the traces of these decisions have been etched into the strata of the city.