Which method provides results that are typically deemed unreliable in lead dust assessment?

In lead dust assessment, micro-vacuuming tends to yield results that are often considered unreliable. This method involves collecting dust samples using a vacuum equipped with specific filters. While it can be useful for general dust collection, the results can be heavily influenced by various factors such as the vacuum's efficiency, the type of filters used, and how thoroughly the surface was vacuumed.

In contrast, wipe sampling is a direct method that collects dust from surfaces for analysis, making it a more reliable indicator of lead dust presence. Air testing focuses on airborne lead concentrations, but it measures lead that is currently suspended in the air rather than lead dust settled on surfaces. Visual inspection can help identify areas where lead may be present but does not provide quantitative data about lead dust levels. Therefore, while the other options provide more direct, reliable methods of assessing lead dust, micro-vacuuming is less dependable due to these inherent variables affecting the sampling process.