PCM and TEM are used for sampling in asbestos work. Which statement best describes their roles?

• A. PCM counts asbestos fibers in air samples to estimate exposure; TEM identifies fiber type.
• B. TEM identifies fiber type and confirms asbestos presence; PCM is used for regulatory decisions.
• C. PCM counts asbestos fibers in air samples to estimate exposure; TEM identifies fiber type and confirms asbestos presence, used for regulatory and clearance decisions.
• D. Neither PCM nor TEM are used in asbestos sampling.

Answer: (C)

The main idea is that two microscopy methods serve different but complementary purposes in asbestos sampling. Phase-contrast microscopy (PCM) is used to count airborne fibers and estimate worker exposure by concentration, but it cannot reliably identify whether those fibers are asbestos. Transmission electron microscopy (TEM), on the other hand, has the resolution and features needed to identify the fiber type and confirm the presence of asbestos. Because of that identification capability, TEM results are applied in decisions about regulatory compliance and the clearance of asbestos-contaminated spaces. So the best description is that PCM counts fibers to gauge exposure, while TEM identifies fiber type and confirms asbestos presence, aiding regulatory and clearance decisions. The other statements misstate PCM’s role or TEM’s capabilities, or imply neither method is used, which isn’t accurate.