Phase Contrast Microscopy (PCM) and Polarized Light Microscopy (PLM) differ in that PCM is used to analyze air samples and PLM is used to analyze bulk samples.

• A. PCM analyzes air samples; PLM analyzes bulk samples
• B. PLM analyzes air samples; PCM analyzes bulk samples
• C. Both analyze air samples
• D. Both analyze bulk samples

Answer: (A)

The key point is that these two microscopy techniques are used for different kinds of samples in asbestos work: phase contrast microscopy is the standard method for counting asbestos fibers in air samples collected on filters, providing a concentration of fibers per unit volume of air for exposure assessment. It’s focused on quantification from air monitoring and doesn’t identify the mineral type. Polarized light microscopy, on the other hand, is used to examine bulk materials to identify asbestos-containing substances, leveraging the distinctive optical properties of asbestos minerals under polarized light to confirm presence and type in solid materials. Because of these intended uses, stating that PCM analyzes air samples and PLM analyzes bulk samples accurately describes their primary roles. The other options mix up the sample types, which isn’t consistent with how these methods are typically applied.