How is asbestos identified in Category I nonfriable ACM?

Asbestos is identified in Category I nonfriable asbestos-containing materials (ACM) when it contains more than 1% asbestos as determined by Polarized Light Microscopy (PLM). Category I materials are generally considered to be low-risk because they are not readily crumbled or pulverized into a powder under normal handling, yet the presence of asbestos at significant levels necessitates following safety guidelines for management and disposal.

Testing for asbestos content using PLM is a reliable and standardized method that allows for precise identification of asbestos fibers within a sample. If a material is found to contain more than 1% asbestos, it must comply with OSHA and EPA regulations, which dictate how such materials should be handled to minimize risk to health.

The other options do not accurately describe the identification process for Category I nonfriable ACM. For instance, while there may be materials with less than 0.5% asbestos, they do not meet the criteria for regulation under most asbestos laws and therefore are typically not classified as ACM. Visual identification alone without testing is not definitive; materials that may appear similar can have different asbestos contents. Finally, materials mixed with non-asbestos materials can still contain significant asbestos content, and their classification depends on the percentage rather than their mixture.