More study is needed to determine whether pollution mitigation efforts at the Union Pacific Roseville rail yard are working, according to the latest results from a long-term monitoring effort.

The results were presented recently to the Placer County Air Pollution Control District as part of the Roseville Rail Yard Air Quality Study, intended to just how much pollution is emitted from the yard – and whether that pollution is decreasing, increasing or staying the same over time.

But analysis of data at several sites located upwind and downwind from the yard failed to show a conclusive trend in several pollution categories during the past three summers ending in 2007, including diesel particulate matter and nitrogen oxides.

“We don’t know,” said Yushuo Chang, Planning and Monitoring Manager for the APCD. “Based on the data, we can’t tell if we can verify results for the mitigation efforts.”

For instance, at one monitoring station located on Church Street, particulate emissions – which health officials suspect in lung cancer – fell in 2007 over 2006 levels, but were still higher than in 2005.

“Based on these reports, we did not see a very clear pattern there,” Chang said.

That means the program, which was slated to end in summer 2007, will be extended. Data collection has continued throughout this summer and funding, through UP and air quality agencies, has been secured to analyze the results.

Chang said one reason more study is needed is because stringent new diesel regulations weren’t fully implemented at the rail yard until after the final study period was completed. That means any benefits seen from the ultra-low-sulfur diesel wouldn’t have shown up yet.

Still, there are hopeful signs. Chang said rail yard traffic increased in 2007 over 2006, but measured pollutants did not appear to increase. “If our trend analysis showed no increased trend, it must mean something happened in the rail yard because they did increase,” he said.

Union Pacific has touted a number of environmental initiatives in recent years. They include more efficient next-generation locomotives, reduced idling and more efficient scheduling. Officials are keen on seeing how well they’re working to reduce emissions because of the large population living downwind of the site, and already established evidence pollution levels higher than what health experts are comfortable with.

"The question is, do they really reduce emission enough for to reduce the risk?” Chang said.

The monitoring effort is part of a landmark deal struck with UP to voluntarily reduce rail yard emissions by 10 percent. That deal followed a 2004 study issued by the California Air Resources Board, which found diesel particulate emissions from the rail yard would increase the risk of cancer diagnoses at a rate of 500 additional cases per million people in some areas. (The rate of cancer for all cases in the general population is 200,000 to 250,000 per million people, according to the study.)

The UP rail yard in Roseville is the largest of its kind west of the Mississippi.