40 CFR Part 763, Appendix A

40 CFR Part 763, Appendix A is the section of the U.S. federal regulations that sets out the official laboratory method for identifying asbestos in bulk building materials using polarized light microscopy (PLM). It tells labs exactly how to prepare a sample, what optical properties to measure, and how to report the percentage of asbestos found. Schools and many other building owners are required to use this method when testing suspect materials.

Origin

This appendix was issued by the U.S. Environmental Protection Agency (EPA) under the Asbestos Hazard Emergency Response Act (AHERA) of 1986, which directed EPA to create rules for inspecting and managing asbestos in schools. The PLM procedure in Appendix A was finalized in 1987 and has remained the federally required bulk-sample method, though EPA later acknowledged its limitations for very low asbestos concentrations.

Significance in Asbestos Context

For patients trying to prove where their exposure came from, Appendix A is often the rulebook behind the lab reports that identify asbestos in floor tiles, joint compound, insulation, plaster, or ceiling materials from a school, workplace, or home. Reports prepared under this method can become evidence that a specific product or building material contained asbestos at the time of exposure. It is also important because the method has known weak points, particularly its difficulty detecting thin chrysotile fibers and low concentrations in materials like vinyl floor tile, which is why defendants sometimes argue a product was "non-asbestos" based on a single PLM result. Your legal team may need an expert to explain when supplemental methods like TEM (transmission electron microscopy) are required to give an accurate picture.

Example Sentence

The industrial hygienist testified that the joint compound samples from the plaintiff's former job site were analyzed under 40 CFR Part 763, Appendix A and confirmed to contain 3–5% chrysotile asbestos.

Related Terms

AHERA, Polarized Light Microscopy (PLM), Transmission Electron Microscopy (TEM), Chrysotile, Bulk Sample Analysis, EPA

Notes

• If you or a family member worked in or attended a school built before 1989, ask whether AHERA inspection records and bulk-sample lab reports still exist. School districts are required to keep an asbestos management plan on file.
• When reviewing any lab report referenced in your case, look for the phrase "EPA 600/R-93/116" or "40 CFR Part 763 Appendix A" to confirm which method was used, and ask your attorney whether TEM confirmation was performed for floor tiles or other vinyl products.
• Preserve any old building inspection reports, renovation records, or product samples you may have. These documents often reference Appendix A testing and can help identify the specific asbestos-containing products you were exposed to.