Do the bright red areas on LiDAR mapping indicate very high levels of dust?

No. LiDAR measures all particulate matter in the atmosphere. It does not differentiate between types of particulate matter including dust (PM₁₀, PM_2.5), water vapour, and other suspended particulates and solid objects. When the LiDAR beam intersects with infrastructure (buildings, equipment) at the elevation plane of the LiDAR monitor, the heat map appears as red and could be interpreted as dust particles. That is, the visual representation is not accurate and can easily be misread. The same could apply during period of rain when the LiDAR pulse if reflected by water droplets.