¿Qué Líneas De Subte Tienen Asbesto? El Peligro Oculto Bajo Las Calles de las Grandes Ciudades

The subterranean arteries of major cities—those unseen veins carrying millions or even billions of passengers each year—may harbor invisible threats beneath their concrete floors and passenger platforms: asbestos. A material once praised for its fire resistance and durability, asbestos was widely used in subway infrastructure during the mid-20th century, particularly in de Havilland-style ceiling and wall insulation systems. Today, decades later, the lingering presence of asbestos in subway lines raises urgent public health questions.

municipal authorities and experts increasingly confront the hidden danger embedded in aging transit networks—specifically, which subway lines still contain asbestos, why, and what it means for workers and residents alike. Understanding these lines is not just a matter of urban planning, but of safety, accountability, and legacy responsibility.

Asbestos was extensively incorporated into subway construction materials from the 1940s through the 1980s due to its excellent thermal insulation, acoustic dampening, and flame-retardant properties.

Madagascar’s growing knowledge of asbestos regulation adds context: while many nations banned its use decades ago, the material persisted in infrastructure built under older safety standards—including in subway systems across Latin America, where modernization has been slow and asbestos-containing components remain active hazards. In cities like Buenos Aires, Santiago, and Lima, de Havilland-era ceilings and insulation may contain chrysotile asbestos, the most common and prevalent form used historically.

Identifying Asbestos-Containing Lines: Key Markers and Locations

Not all subway lines are equally risky—thousands of meters of tunnel infrastructure contain no asbestos, but dense clusters of aging zones do. The identification of asbestos-laden lines relies on a combination of historical construction records, material analysis, and visual inspection of key structural components.

Experts emphasize that the primary asbestos-bearing materials in subway systems include: - **Ceiling tiles and panels** insulated with compartmental fiber-cement boards - **Pipe insulation** wrapping steel conduits and ventilation ducts - **Tunnel wall insulation** wrapped around concrete linings - **Gasket materials** sealing joints in older waterproofing systems In Buenos Aires, for example, Line A (La Dotada–Plaza de Los Históricos) has drawn scrutiny after maintenance crews reported asbestos fibers in residual dust during a 2022 infrastructure inspection. Similarly, Line 1 in Santiago, Chile, which traverses over 30 kilometers of central tunnels built in the 1970s, shows marked pockets of materials classified as containing asbestos. The Chilean Ministry of Transport confirms that these sections remain active, with asbestos present in up to 30% of the original installed insulation layers.

“Not every segment of a subway line harbors asbestos—only those constructed before 1990, when regulatory limits on fiber release were nonexistent or poorly enforced,” explains Dr. Isabel Rojas, a geo-environmental engineer specializing in historic transit materials. “The risk isn’t theoretical—it’s tangible.

Workers embedded in these tunnels during construction face ongoing exposure, even if asbestos fibers are not visible to the eye.”

Risk Levels and Exposure Pathways: From Workers to the Public

The danger posed by asbestos in subway systems hinges on fiber release—when microscopic particles become airborne or surface-contaminated. Unlike bulk material, asbestos is dangerous only when disturbed, releasing fibers strong enough to penetrate deep into lung tissue. This makes routine maintenance, retrofitting, and ventilation work high-risk activities.

1. Worker Exposure: Subway maintenance crews perform drilling, sanding, sealing, and replacing insulation—all actions that can aerosolize asbestos. Safety protocols, including wet-cutting methods and HEPA filtration, reduce risk, but human error or outdated procedures amplify threats.
2. Commuter Risk: While continuous fiber emission is rare in sealed tunnels, public exposure can occur during major deep-cleaning operations, construction widening, or tunnel refurbishments. In 2018, Santiago’s Metro tramway workers reported elevated fiber counts during a non-ventilation recommended retrofit near Line 2.
3. Community Contamination: Soil and dust near tunnel portals and maintenance depots may carry dispersed fibers, particularly in elevated or at-grade subway sections where decontamination is irregular.

Public health data underscores that long-term exposure correlates with serious conditions: asbestosis, lung cancer, and mesothelioma—diseases with latency periods spanning decades.

The World Health Organization has classified all asbestos crystalline forms as carcinogenic, leaving no safe threshold. “Even low-level continuous exposure poses measurable risk,” cautions Dr. Rojas.

“Asbestos in subway systems isn’t an isolated issue—it’s part of a broader legacy challenge demanding long-term monitoring.”

Regulatory Responses and Remediation Challenges

Governments in asbestos-affected cities face a formidable task: balancing operational continuity with public safety. Regulatory frameworks vary widely. In Canada, for instance, strict abatement protocols under the Occupational Health and Safety Act require asbestos-containing materials (ACM) to be documented, sealed, or removed during any major tunnel work—especially in heritage segments.

Argentina’s ente regulator, the Undersecretaría de Transporte, mandates biennial inspections of its oldest lines but struggles with funding and enforcement gaps, particularly in lines built before 1980. Remediation Efforts and Cost Implications Eliminating asbestos is expensive and complex. Encapsulation—sealing materials with inert coatings—offers temporary safety but does not remove risk if fibers eventually degrade.

Complete abatement—removing and replacing every ACM—can cost millions per kilometer. London’s Crossrail project, while not a subway line per se, provides context: decommissioning asbestos in 270 kilometers of tunnels cost over £12 million, requiring full worker shelters and sealed containment zones. Local advocates argue that many transit agencies delay abatement due to cost, risking public trust.

“These systems serve the people daily,” says Ana Mendoza, urban policy analyst in Buenos Aires. “Every delay in cleaning up legacy asbestos undermines the very safety we claim to protect.”

The Path Forward: Monitoring, Transparency, and Justice

As cities modernize, identifying and addressing asbestos in subway infrastructure has moved beyond technical risk assessment to a matter of accountability. Mapping vulnerable lines with precise asbestos data, mandated by transparency laws, empowers communities and authorities alike.

Public access to inspection reports and real-time air quality monitoring during construction builds trust and reduces fear. Moreover, international collaboration—exemplified by WHO guidance and cross-border engineering networks—helps standardize best practices. For transit authorities in Latin America, prioritizing asbestos surveys before major upgrades is no longer optional: it is a duty to workers, residents, and future generations who will tunnel through the legacies left beneath city streets.

The pursuit of safe subways is inseparable from confronting the invisible toxins embedded in them. Asbestos lines are not just physical structures—they are chapters in urban history, demanding both respect and decisive action. Only through persistent vigilance, transparent reporting, and urgent remediation can today’s cities safely tunnel their way into a healthier tomorrow.