Tokyo Metro Hanzomon Line Resumes After Asbestos Found at Station on August 9

Tokyo Metro halted the Hanzomon Line between Shibuya and Kudan-Shita stations for approximately 14 hours on August 11 after discovering asbestos-containing material at Hanzomon Station in Chiyoda Ward. The fabric, measuring roughly 40 centimeters by 30 centimeters, fell from damaged ventilation equipment on August 9. The operator completed repairs, cleanup, and environmental testing before resuming full service at 7:20 p.m.

How the asbestos fabric fell into the station

On August 9 at 5:55 a.m., the fabric joint in the ventilation equipment at Hanzomon Station partially broke. The damaged section, approximately 40 centimeters long, 30 centimeters wide, and 0.3 centimeters thick, became caught in the rotating fan. Thread fragments fell from the air conditioning outlet onto the station platform. Tokyo Metro stopped part of the ventilation system and repaired the damage by 8:40 a.m.

Why the line shut down for 14 hours on August 11

After testing, Tokyo Metro determined the fallen threads contained asbestos, a carcinogenic substance. The operator suspended service between Shibuya and Kudan-Shita stations from the first train on August 11 and closed Hanzomon Station. Specialist contractors removed the contaminated material and cleaned the platform. Environmental measurements confirmed safety under Ministry of Environment guidelines before service resumed at 7:20 p.m.

Impact on other transit lines and passenger support

The Hanzomon Line suspension disrupted the Tokyu Den-en-toshi Line and Tobu Skytree Line, which operate through-service on the Hanzomon Line. Both lines halted through-service and operated partial routes. Tokyo Metro established a customer service center to address concerns from passengers who used or passed through Hanzomon Station and apologized for the disruption.

What asbestos is and why it matters

Asbestos was once widely used in construction materials for its fire resistance and insulation properties. The World Health Organization classifies it as a carcinogen because inhaling fibers causes lung cancer and malignant mesothelioma. Japan has principally banned asbestos manufacturing due to health risks. Exposure effects often appear years after contact.

Final Thoughts

Tokyo Metro’s swift response prevented prolonged exposure and restored service within 14 hours. The incident highlights ongoing asbestos risks in aging infrastructure across Japan’s transit systems.

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