Intermodal Cancer Risks

Study confirms cancer risk near UP's Roseville railyard Highly toxic particles make train exhaust worse than diesel truck emissions, scientists say. By Chris Bowman - cbowman@sacbee.com Published 12:00 am PST Thursday, November 29, 2007 Air test results released Wednesday confirm that residents living near the Union Pacific Railroad yard in Roseville face a sharply higher cancer risk from locomotive exhaust than those living along nearby Interstate 80, a stretch traveled by an average 10,000 big rigs a day. The spew from idling locomotives contains 5.5 times more of the most toxic particles than emissions from diesel-powered trucks on freeways, the study said. "The diesel train stuff is much richer in the nastiest material," said Thomas A. Cahill, a retired UC Davis professor of atmospheric physics. The study recommended several ways to lower residents' health risks. Paving the railyard would cut down toxic dust. Planting rows of tall trees along the edges of the yard would filter out a good portion of the exhaust particles, as would the installation of electrostatic air filters in homes. The highly hazardous exhaust particles are polycyclic aromatic hydrocarbons, or PAHs, which California has classified as cancer-causing compounds. An extensive health study published last month found a strong link between bronchitis and elevated levels of these air pollutants among preschool children. Cahill said he was alarmed to find airborne particles of benzo-a-pyrene – considered the most hazardous PAH compound – consistently measuring much smaller than those found in truck exhaust. The particles are small enough to reach the deepest recesses of the lungs, where they can cause the greatest harm. "The lung captures these particles with extreme efficiency and retains them," said Cahill, co-leader of the project with his son, Thomas M. Cahill, an assistant professor of environmental toxicology of Arizona State University. The scientists traced the source of these compounds to burned engine oil, which is spewed from the stack as part of the locomotive exhaust. "Now that we know where it comes from, we can talk seriously about mitigation," Cahill said. "It opens up research into making an oil compound or changing the way you handle oil in a train." The samplers also found unexpectedly high levels of toxic metals such as lead. They said the metals likely came from the dirt surfaces of the train yard, where locomotives have been serviced for 100 years. "The dust blown off the railyard is full of all sorts of stuff, even bomb debris from who-knows-what," Cahill said. On April 28, 1973, several 250-pound bombs bound for Vietnam exploded aboard a freight train in the railyard. Live bombs were found buried in the area as late as 1997. The Cahills did the peer-reviewed air sampling and analysis earlier this year on behalf of the Sacramento area chapter of Breathe California, a clean-air advocacy group. The U.S. Environmental Protection Agency funded the project. One of the reviewers, Ralph Propper, an air pollution researcher at the state Air Resources Board, said he was surprised by the findings. "It's a red flag that the PAHs that we know are the most potent components of diesel exhaust are elevated more than fivefold," Propper said. "It makes you concerned that the overall toxicity of diesel is higher than you suspected." Cahill said his air measurements are consistent with findings from a 2004 air board computer analysis of the train yard exhausts. The study found locomotive exhaust extended about 100 square miles – encompassing most of Roseville, all of Citrus Heights and all of Antelope – and raising the cancer risk for an estimated 165,000 residents. For example, living within 300 feet of the yard's locomotive service and repair center boosts the cancer risk an average 950 chances in a million, the state analysis showed. By comparison, living within 300 feet of I-80 in Roseville increases the cancer risk 50 to 100 chances in a million, according to the air board study. About 100 locomotives occupy the 780-acre yard at any given time, Union Pacific officials said in 2005. About one-quarter of those are part of trains passing through en route to Portland, Reno or Sacramento. Others stop to switch tracks, reassemble cars or crews, refuel or undergo inspection, repair or testing.