State and local pollution officials have branded diesel exhaust a major cancer risk and have asked the U.S. Environmental Protection Agency to tighten standards on diesel emissions.

“There is no pollution more disgusting that the thick, noxious, suffocating smoke that
billows from trucks and buses,” stated William Becker, executive director of the State and Territorial Air Pollution Program Administrators and the Association of Local Air Pollution Control Officers in a March 15 press release. “But even worse, these fumes are putting us at risk of cancer -- a risk that can be almost completely eliminated with modern pollution controls.”
Becker based his statements on an analysis done by STAPPA/ALAPCO which concludes
that more than 125,000 people “may get cancer from the dirty diesel exhaust from trucks, buses and other diesel engines.” An estimated 119,570 of those will be people living in the country’s 50 largest metropolitan areas.
Even before the study was officially released it was drawing headlines like “Diesel Exhaust Cause Cancer” from major news agencies; but criticism and controversy is sure to follow. The methodology portion of the study begins with an admission that “there is no method for measuring diesel particulate directly.” Instead, researchers relied on a methodology used by the California Air Resources Board which, in a draft report released last year, attributed 70% of the total cancer risk to diesel particulates. The Engine Manufacturers Association said that report contained “significant uncertainties and errors” in the way health risks were determined.
But Becker said that the STAPPA/ALAPCO estimate is “extremely conservative” and that
“the actual number of cancers could easily be ten times higher.” The important thing, he
adds, “is that we are facing a cancer risk - a risk we cannot avoid unless EPA takes
decisive action.”
One recommendation STAPPA/ALAPCO sent to EPA Administrator Carol Browner is that California’s strict new diesel sulfur standards for bus engines be adopted nationwide by 2006. The groups also want tougher nitrogen oxide and particulate limits. New diesels currently put out an average 4 grams NOx per brake horsepower hour and 0.10 grams of particulates. EPA has proposed a combined maximum of 2.4 grams with possible further reductions, possibly 0.5 grams or less for NOx and 0.01 for particulates. STAPPA/ALAPCO recommends 0.2 grams for NOx and 0.01 for particulates by 2007.
STAPPA/ALAPCO also urged EPA to impose highway diesel emissions rules for non-road vehicles, such as construction equipment and to “make sure big diesel trucks, bus and nonroad engines operate as cleanly in use as they are supposed to.”
A copy of the study is available at the STAPPA/ALAPCO web site,