According to the US EPA, when is asbestos deemed potentially hazardous?

The identification of asbestos as potentially hazardous primarily revolves around its physical state. When asbestos is in a friable state, it means that the material can easily crumble, powder, or become airborne when disturbed. This condition significantly increases the risk of exposure to asbestos fibers, which can lead to serious health issues when inhaled.

In contrast, when asbestos is completely sealed or encapsulated in materials like plaster, it is generally considered to be in a non-hazardous condition because the fibers are not accessible to the air or to individuals who might disturb it. Low concentrations of asbestos also do not necessarily pose an immediate risk as the danger arises primarily from the potential for release of fibers into the air. Therefore, friable asbestos represents the highest risk level, making it the correct identification of when asbestos is potentially hazardous according to the US EPA guidelines.