Agricultural operations across the United States are encountering difficulties in complying with the current air pollution regulations for particulate matter (PM). The National Ambient Air Quality Standards (NAAQS) for PM in terms of PM₁₀, are ambient air concentration limits set by EPA that should not be exceeded. Further, EPA and State Air Pollution Regulatory Agencies (SAPRA’s) utilize the NAAQS to regulate criteria pollutants emitted by industries by applying the ambient air concentration limits as a property line concentration limits. The primary NAAQS are health-based standards and an exceedance of the NAAQS implies that it is likely that there will be adverse health effects for the public. The current PM₁₀ primary 24-hour NAAQS is 150 micrograms per actual cubic meter (μg/acm). Prior to and since the inclusion of the PM₁₀ indicator into the PM regulation, numerous journal articles and technical references have been written to discuss the epidemiological effects of PM, trends of PM, regulation of PM, methods of determining PM₁₀, etc. A common trend among many of these publications is the use of samplers to collect information on PM. All to often, the sampler data are assumed to be an accurate measure of PM, when in fact issues such as; sampler uncertainties, environmental conditions, and material characteristics for which the sampler is measuring must be incorporated for accurate sampler measurements. The focus of this manuscript is on the errors associated with material characteristics or particle size distribution (PSD) of the material in the air that is being sampled, the assumptions associated with PSD’s and sampler performance characteristics, and the interaction between these two characteristics. The common perception is that PM₁₀ measurement concentrations relate to true concentrations (also refereed to as virtual-cut concentrations) or PM with particle sizes less than 10 μm aerodynamic equivalent diameter (AED). However, these measurement concentrations are actually based on sampler measurements. PM₁₀ samplers bias the concentration measurements, since a portion of the PM less than 10 μm will not be collected on the filter and a portion of the PM greater than 10 μm will be collected on the filter. A common assumption made in the regulatory community to circumvent this problem is that the mass of particles less than 10 μm and captured by the pre- separator are equal to the mass of particles greater than 10μm and captured on the filter. This issue leads to a primary focus of this manuscript, that is, industries that emit PM with a mass median diameter (MMD) less than 10 μm are not regulated at the same level as agricultural operations, which typically emit PM with an MMD greater than 10 μm. This unequal regulation is primarily due to the interaction of the sampler performance and PSD characteristics. For example, if property line sampler concentration measurements from two industries are exactly the same and if 100% of industry A’s PM is less than 10 μm and 38% of industry B’s PM is less than 10 μm (true PM₁₀); then 100% industry A’s PM can potentially reach the alveolar region of the lungs as compared to 38% of industry B’s PM. Since the emphasis of the primary NAAQS is to protect public health; then in the previous example the two industries are not equally regulated. Therefore, in order to achieve equal regulation among differing industries, PM₁₀ measurements MUST be based on true concentration measurements.