and also in a scientific - practical sense:

there are important distinctions between filterable and condensable PM2.5. Further, some methods used to measure PM emissions reflect only the filterable components and, to exacerbate the problem, the filterable components vary depending on the test method used.

The first step in any attempts to mitigate the FPM content in the air is to monitor the sources, flow, composition etc of the particles. From the EPA document:

The importance of determining source apportionment for ambient PM2.5 in a specific area cannot be overstated; developing a cost-effective approach to controlling PM2.5 emissions sources requires an understanding of the relative contribution from local and regional sources. Adequate monitoring data are needed to provide insight into the composition of ambient PM2.5 in a given area.

A British document Fine Particulate Matter (PM2.5) in the United Kingdom (2012), states the reason why action is not happening fast enough reasonably well, with

The science underpinning the knowledge of PM2.5 is rapidly evolving and remains uncertain in many areas. There is a need for rapid translation into the policy arena of the newest results and understanding.

The uncertainty due to the varying compositions, which in turn affect how the particles move, how they interact with the surrounding environment suggests that 1 method would not be sufficient, and that more localised methods of control are necessary.

As you suggested, the importance of understanding FPM can not be understated, in epidemiological research Reduction in Fine Particulate Air Pollution and Mortality Extended Follow-up of the Harvard Six Cities Study (Laden et al. 2006), there have been found to be a drop in mortality corresponding to a drop in FPM concentrations.