Diesel engines are the predominant choice when moving freight, particularly for the railroad industry. Compared to gasoline engines, diesel emits relatively few of the toxic compounds generally associated with internal combustion. However, diesel engines produce a disproportionate quantity of particulate aerosols. Airborne pollutants from locomotives and freight transferring equipment in railyards significantly impact the air quality of surrounding neighborhoods. We summarize the health impacts of diesel particulates emitted from railyards in Oregon. Using the most conservative range of the EPA's assessment, we calculate a Pigouvian Tax for the railroad companies to pay, totaling $624.24 per μg/m 3 for each person in the affected area.