Environmental ▼News Study raises questions about diesel emissions esults from a first-of-its-kind trailer, the Riverside researchers “If one assumes that the organic mobile laboratory reveal that made the first reported on-road fraction dominates the carcinogenic the composition of particulate measurements of elemental carbon and toxic effects of the diesel PM, emissions from heavy-duty diesel (EC) and organic carbon (OC) fracthe human health risk increases trucks depends strongly on how the tions of particulate emissions from almost an order of magnitude in vehicle is operated. Experts specuheavy-duty diesel truck engines. highly congested traffic as comlate that the findings, published in They found that trucks emit 8.1 pared with free-flowing traffic,” this issue of ES&T (pp 2544–2550), times more OC and 1.9 times more the authors wrote in the paper. may provoke changes in current EC per mile sitting in traffic than Voluntary and regulatory stanmodels and human health risk ascruising at higher speeds on the dards as part of the Diesel Risk sessments and even in how we plan highway. Reduction Program are already in our neighborhoods. place to reduce Traditionally, emissions from emissions from mobile and staheavy-duty diesel tionary diesel envehicles are collectgines within the ed and measured next decade, but in stationary labs. “if you could conOther groups have trol the traffic flow tried using “chase of heavy-duty diesel vehicles” to quanvehicles to times tify truck emissions that are free-flow under real-world or less congested, conditions. Howyou could reduce Researchers at the University of California, Riverside, packed equipment to ever, researchers the organic emiscollect emissions from a diesel tractor into a 53-foot trailer. at the University sions rates by of California, Riverside, managed to Although the OC fraction con80–90%,” says Cocker. cram into a 53-foot trailer all of the tains most of the mutagenic and The University of Denver’s equipment required to comply with carcinogenic chemicals in the air, Donald Stedman, one of the onthe California Air Resources Board’s scientists have traditionally used EC road testing pioneers, commends (CARB) latest testing protocol for as a marker for human exposure to the study. Although he is curious diesel particulate emissions. A doudiesel exhaust. Modelers and risk whether these results represent ble-insulated metal “snorkel” diassessors also assumed that the the whole fleet and all its emisrects the exhaust of the diesel truck ratio of EC to OC remains constant. sions, he adds that these kinds cabs—which are known as tractors— That assumption “may be flawed,” of results “will help us to write into the mobile lab trailer where says Joseph Norbeck, director of the intelligent regulations.” automated equipment collects Center for Environmental Research Or help us create communities data, leaving little doubt about the and Technology at Riverside and a more intelligently, says Timo Ålanorigin of the emissions (Environ. paper coauthor. We found that “the der, a research scientist who invesSci. Technol. 2004, 7, 2182–2189). ratio changes dramatically, dependtigates diesel emission studies at David Cocker, the paper’s correing on the operation of the vehicle,” the University of Kuopio in Finland. sponding author, says that his he says. “This information should be exgroup spent three years working The Riverside researchers say ploited in traffic planning, includout how the sensitive equipment that their new data’s implications ing how the roads and residential dealt with literal bumps in the road. for health policy could be dramatic. areas are situated.” For example, A professional driver operated For example, the CARB’s assessment warehouses that supply trucks 11 different tractors through four for cancer risk from diesel particushould be near highways and away modes: idle, creep (congested traflate matter (PM) assumes that the from residential areas. fic), transient (lower speeds), and amounts of OC and EC are identical The Riverside researchers plan cruise (highway travel). when a truck is driving on a highto evaluate train and jet engines Using their specially designed way and when it is idling. Therefore, next. —RACHEL PETKEWICH ANIKET SAWANT
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152A ■ ENVIRONMENTAL SCIENCE & TECHNOLOGY / MAY 1, 2004
© 2004 American Chemical Society
