(The following story by Nathan Donato-Weinstein appeared on The Press-Tribune website on December 4.)
ROSEVILLE, Calif. — When it comes to air pollution, not all diesel emissions are created equal.
That’s one of the key findings of a new air quality report released last week that fingers Union Pacific’s J.R. Davis Rail Yard for abnormally high concentrations of certain cancer-causing particles – including up to 5.5 times more carcinogenic material from rail diesel exhaust than that from trucks – in areas downwind of the massive train facility.
But the study, released last Wednesday, quickly came under fire from Union Pacific officials, who last week questioned its validity by saying the report’s authors did not adequately account for so-called “confounding factors,” such as other nearby pollution sources.
The report was issued by the Sacramento-Emigrant Trails chapter of Breathe California, a nonprofit health advocacy group, and led by retired UC Davis atmospheric physics scientist Thomas A. Cahill and his son, Thomas M. Cahill, an environmental toxicologist at Arizona State University.
Using monitoring equipment set up near Denio’s Farmer’s Market & Auction and Johnson Pool in Roseville, as well as publicly available information from an ongoing Placer County-led monitoring project, the report details how exhaust from diesel locomotive engines at the rail yard appears to be more toxic than exhaust from truck diesel engines, due to heavier concentrations and more damaging molecular weights of pollutants, the study’s authors said.
For instance, the report found up to 5.5 times more benzo-a-pyrene, a notorious carcinogen known as a polycyclic aromatic hydrocarbon, or PAH, and long implicated in a range of cancers, than what’s emitted by diesel trucks. The authors speculate the source of those emissions is the burning of engine lubricating oil.
The study further reports soil contamination at the rail yard showed up later outside of the area – the result, researchers believe, of contaminated soil being “re-suspended” by activity such as vehicle traffic. “This is not a real happy report,” Thomas A. Cahill said last week. “The fact that diesel gas is qualitatively different than truck exhaust – that’s a shocker.”
In addition to presenting data, the report’s authors suggest a number of mitigation strategies for rail yard pollution, from simple things such as vegetation barriers near the yard to filter air, to alternative fuels and implementing hoods to capture and “scrub” locomotive exhaust.
The new survey of the rail yard’s environmental impact follows a major study commissioned by the California Air Resources Board that was released in 2004. That survey compiled four years of data on how diesel particulate emissions from trains move through the air, and found rail yard emissions reaches out for nearly 100 square miles. It concluded that diesel particulate emissions from the rail yard would cause cancer at a rate of 500 cases per million people, compared to the rate of cancer for all causes, at 200,000-250,000 per million.
The 2004 study also led to an agreement among the railroad, Placer County and other agencies to reduce rail yard pollution while monitoring the effort. The latest study comes at the tail end of the monitoring project, which is set to end this year.
Cahill said the new study was sparked by a desire to add to the understanding of how rail yards affect pollution for those nearby, and to study additional pollutants not included in the 2004 report.
“We felt the results of the 2004 study pointed to serious diesel-based toxics,” he said.
However, Union Pacific took issue with many of the report’s findings. Gary Rubenstein, a senior partner at Sierra Research and Union Pacific’s representative on the technical advisory committee for the ongoing monitoring project, said the latest study’s results rely on data collections that at times were not able to identify the source of pollution as the rail yard. Although he doesn’t deny Cahill picked up the pollution detailed in the study, including benzo-a-pyrine, “It’s not clear that what he’s measuring is what is coming from rail yard,” Rubenstein said. “We have to be really focused that what we’re measuring is the rail yard and not the confounding sources.”
Rubenstein also said a major finding – that rail diesel is dirtier than other forms of diesel – relies on outdated studies of baseline diesel emissions.
“It does not mean locos are 5-6 times dirtier than anybody thought, it means trucks are 5-6 times cleaner than anybody thought,” he said.
For his part, Cahill agrees that more study is needed to confirm the results were coming from the rail yard, and that a simultaneous measurement of truck exhaust on I-80 would provide a more accurate portrait than modeling studies.
“My feeling is our report is kind of like waving the flag up, and saying, ‘look we have a little problem here,'” he said.
Efforts to make the rail yard more environmentally friendly have picked up steam over the past several years. Placer County Air Pollution Control Officer Tom Christofk said last week monitoring and reducing emissions at the yard, part of the MOU that targeted a 10 percent reduction in rail yard pollution, are ongoing. The final report on the project is due next year, but Christofk added officials are studying whether to extend the program.
“Mitigation efforts like upgrading long hauls and switching fuel standard and all those mitigation standards are just being phased in now,” he said. Last year, a first-of-its-kind test of an idling locomotive emissions “scrubbing” system was demonstrated at the J.R. Davis Yard. A report later found the system highly effective in reducing harmful emissions. Union Pacific has not decided whether to implement the system.
Kathryn Blackwell, a company spokeswoman, said: “We as a company are committed to improving the environmental impact to our operations.”