Attainment will require substantial reductions in directly emitted PM10 and PM2.5 pollutants and precursors. During the worst episodes that occur during the winter, secondary nitrate is the largest contributor to the problem followed by geologic material and carbon from wood combustion and motor vehicles. Modeling using UAM-Aero indicates that controls of oxides of nitrogen (NOx controls) are the most effective at reducing nitrate concentrations throughout the air basin. Fugitive dust controls on activities in the urban area are most effective at reducing geologic dust in the areas with the highest readings, although reductions in rural areas may be important to protect people living in proximity to large sources. Controls on residential wood burning will result in substantial reductions in carbon particles in urban areas with high concentrations of wood burning devices. The state and federal motor vehicle program and diesel fuel regulations will also significantly reduce NOx, volatile organic compounds (VOC), diesel particulate and oxides of sulfur (SOx) emissions. Although modeling indicates that VOC controls are not effective in reducing secondary nitrate, existing and planned regulations on VOC sources adopted for ozone may result in some air quality benefit due to reduction in condensable PM emissions from these organic compounds.

Many of the controls needed to attain the PM10 and PM2.5 standards have already been adopted as rules and regulations by the District, the state, local agencies, and the federal government. Some of these regulations are fully implemented while others that rely on equipment/vehicle turnover take many years to make a large impact.