The California Air Resources Board conducted a health risk assessment of airborne particulate matter emissions from diesel-fueled locomotives at the Union Pacific J.R. Davis Yard located in Roseville, California. The results from that evaluation are presented in the Roseville Rail Yard Study. Key findings include: The diesel particulate matter (PM) emissions in 2000 from locomotive operations are estimated to be about 25 tons per year; about half of those emissions come from idling trains; the elevated concentrations of PM contribute to an increased risk of cancer and other cardiovascular diseases such as asthma. To download the study visit //www.arb.ca.gov/diesel/documents/rrstudy.htm.