Asbestos in Sponge Blocks Exposure and Risks

Sponge blocks, also known as foam blocks, were frequently used as insulation material under the roofs of residential and commercial buildings throughout the 20th century. Reinforced with asbestos, sponge blocks were also used in places heat or flames posed a hazard, such as around steam pipes, boilers and furnaces.

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Asbestos in Sponge Blocks Explained

Asbestos was highly praised throughout the 20th century for superior qualities such as:

  • Insulative properties
  • Resistance to heat and flames
  • Lightweight
  • Durability
  • Low cost

Because of these attributes, asbestos was added to thousands of consumer and industrial products manufactured in the United States and around the world.

Did You Know?

University of Wisconsin Case Study

According to the University of Wisconsin’s maintenance department, asbestos block insulation was installed as late as the mid-1970s, and used to support steam pipes in locations where they hung from joists underneath the floor above.

The University of Wisconsin’s website notes that the material from which its sponge block insulation is made contains a “high-percentage asbestos,” and is likely to become friable if disturbed in any way.

“Friability” is defined as the ability to crush a given material into dust capable of floating in the air with the use of hand pressure alone. Friable asbestos fibers, such as those from sponge blocks, can float in the air for days, but cannot be seen with the unaided eye.

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Who Was Exposed to Asbestos in Sponge Blocks?

The population with the highest risk of asbestos exposure from sponge blocks are the people who worked to manufacture, install and remove sponge blocks.

During the manufacturing process, extremely high quantities of asbestos dust may have been released into the air. Anyone working in the factory environment likely would have inhaled dangerous amounts of asbestos. Because of the friable nature of asbestos-containing sponge blocks, anyone working around these products is at risk of inhaling asbestos fibers.

Additionally, asbestos fibers adhere to skin, hair and clothing and can be carried to secondary environments, such as a home. Spouses, children and pets of people who worked directly with asbestos may also be at risk of asbestos-related diseases.

Many sponge blocks carried asbestos, including products like:

  • Asbesto-Sponge Felt
  • Insulation from H.W. Johns-Manville Company
  • Zonolite® Attic Insulation
Did You Know?

Zonolite® Insulation Contained Asbestos

Zonolite® insulation is made from vermiculite, which on its own does not cause health problems. However, the vermiculite used to make Zonolite® Attic Insulation was extracted from the Libby Mine in Montana—a natural deposit of asbestos which resulted in the vermiculite being contaminated with asbestos.

No vermiculite extracted from the Libby mine has been on the market in the last 10 years. However, vermiculite products from before 2005 may be contaminated with asbestos.

Identifying Asbestos Sponge Blocks in Your Home

If you have reason to believe that asbestos-containing sponge blocks are installed in your home, a number of options are available:

  1. Sealing
  2. Most sources recommend that if asbestos-containing materials are not in a friable state, they should simply be left alone. However, it is highly inadvisable to simply ignore the problem. Asbestos sponge-blocks will ultimately deteriorate over time, placing your health and that of your family at risk.

    Sealing the material with resin is cost-effective and ensures that the sponge blocks do not deteriorate and release asbestos.

  3. Professional Removal
  4. Professional removal can be expensive. However, careful precautions are essential to the safe removal of asbestos. With a professional service, individuals with specialized training use proper protective equipment, seal the environment, and safely remove, transport and dispose of the hazardous material.

  5. DIY
  6. Taking on an asbestos removal project without special training is dangerous. Although homeowners are legally entitled to do their own asbestos abatement on buildings that serve as their primary residence, the work involves extensive preparation.

If the property that contains asbestos is used for rental or is a business into which the general public is allowed, property owners typically must use licensed asbestos contractors or they will face legal penalties.

Access Asbestos Trust Funds

Compensation for treatment, loss of income and other damages are available through Asbestos Trust Funds. Mesothelioma patients exposed to sponge block asbestos may qualify.

Find Out If You Qualify

Health Risks of Asbestos in Sponge Blocks

When invisible asbestos fibers are inhaled, they can attach to the chest and abdominal tissues, cause scarring and are impossible to remove. When someone is exposed to asbestos in high enough quantities, they are at risk of developing a range of health problems, including mesothelioma.

Mesothelioma, cancer in the lining of the lungs, abdomen or heart, is only known to be caused by asbestos exposure. After many decades, the lodged asbestos fibers may trigger genetic mutations that cause tumors to form. By nature, mesothelioma tumors will eventually spread to distant parts of the body.

Specialized treatment plans, including surgery, chemotherapy and radiation, can help slow the disease progression and improve a patient’s quality of life.

Seeking Justice for Mesothelioma

If you have mesothelioma and worked with asbestos-containing sponge blocks, you may be eligible for legal compensation. Asbestos trust funds and other legal avenues may help you receive the financial support you need to cover your treatment costs and other damages.

If you have concerns about asbestos exposure from sponge blocks or other industrial materials, contact the Justice Support Team. Request a FREE Mesothelioma Justice Guide today or call us at (888)360-4215.

Mesothelioma Support Team
Stephanie KiddWritten by:


Stephanie Kidd works tirelessly as a dedicated advocate for the vulnerable and underrepresented. Stephanie worked as a copywriter for an agency whose focus was communicating safety procedures on construction work sites. With her extensive background in victim advocacy and a dedication to seeing justice done, Stephanie works hard to ensure that all online content is reliable, truthful and helpful.

View 5 Sources
  1. Asbestorama, “Vintage HW Johns-Manville Insulation - Asbesto-Sponge Felted,” Retrieved from Accessed on September 19, 2018.
  2. Canada’s Restoration Services, “Asbestos Pipe Wrap and Duct Wrap Removal,” Retrieved from Accessed on September 19, 2018.
  3. General Plastics Manufacturing Company, “Structural Insulation Foam Blocks, “ Retrieved from Accessed on September 19, 2018.
  4. Government of Canada, Canadian Centre for Occupational Health and Safety, “Vermiculite Insulate COntaining Asbestos,” Retrieved from Accessed on September 19, 2018.
  5. Inspectapedia, “Photo Guide to Asbestos Pipe Insulation in Buildings,” Retrieved from Accessed on September 19, 2018.
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