In 2006, EPA set the National Ambient Air Quality Standard (NAAQS) for the coarse fraction of particulate matter (PM) in ambient air. The coarse fraction particles are those particles between 2.5 and 10 micrometers aerodynamic equivalent diameter (AED). The initial proposal was to set the PM_10-2.5 NAAQS at 70 µg m^-3. It was perceived that this would be equivalent to the PM₁₀ NAAQS or 150 μg m^-3. The method used to measure the coarse fraction concentration was the “subtraction” method. This consisted of measuring the PM₁₀ and PM_2.5 concentrations with federal reference method (EPA approved) samplers and subtracting the PM_2.5 concentration from the PM₁₀ concentration. This proposal was a problem for agriculture because very little PM emitted by this industry is PM_2.5. In effect, it would have lowered the regulatory level of ambient PM to less than 50% of the previous level. EPA chose to set the PM_10-2.5 NAAQS at 150 μg m^-3.Much of the PM emitted by agriculture and mining was deemed as crustal (derived from soil). The initial PM_10-2.5 NAAQS proposal was to provide credit for these two industries in the form of a crustal exclusion. The larger soil particles were not perceived to be a health problem for the public. However, there was no objective, scientific procedure to quantify the mass fraction of crustal captured by the sampling methods. This paper outlines the progress made to quantify the mass fraction of crustal in PM coarse concentration measurements using chemical and physical speciation procedures.