Which material is commonly used in insulation but poses severe respiratory health risks if airborne or inhaled?

Asbestos is a mineral fiber that was widely used in building materials and insulation due to its resistance to heat, fire, and many chemicals, as well as its sound absorption qualities. While it was highly effective for insulation purposes, it was later discovered that asbestos poses significant health risks when its fibers become airborne and are inhaled. Exposure to asbestos can lead to severe respiratory diseases, including asbestosis, lung cancer, and malignant mesothelioma. These health risks are particularly concerning because the fibers can remain in the air for a long time and can be inhaled without any immediate symptoms, leading to long-term health effects.

In contrast, fiberglass is generally considered safe for use in insulation, as it does not pose the same health risks as asbestos, although it can cause skin irritation or respiratory issues if fibers are inhaled in significant quantities. Polyurethane and cellulose also present safety profiles that do not involve the same severe respiratory health risks associated with airborne particles. Thus, asbestos is distinctly known for its hazardous nature when disturbed or deteriorated, making it the correct answer for this question.