LOS ANGELES — The report on diesel emissions released by the Natural Resources Defense Council is fundamentally flawed, according to the manufacture of Green Diesel TechnologyT buses, International Truck and Engine Corporation.
“We agree with NRDC that we should retire these older, more polluting buses as fast as possible–we just differ on how to go about doing it,” said Trueblood, Manager of Public Affairs International for International Truck and Engine Corporation. Trueblood added, “California has the oldest school bus fleet in the nation. The best way to ensure that school kids ride on safe buses is to invest in new, clean buses – fueled by clean diesel OR natural gas.”
The report leads people to believe that exhaust fumes inside old, 1980’s diesel school bus pose a serious health risk to children, and that therefore school districts should abandon diesel technology altogether and purchase compressed natural gas buses.
“Green Diesel TechnologyT buses release a lower level of particular matter than natural gas buses,” said Trueblood. “They offer a cost effective way for schools to meet their transportation needs while reducing air pollution.”
“This study sampled only four 20-year old buses,” said Trueblood. “The purported results conflict with many other studies in the field, including a recent study by the respected European research firm EcoTraffic, which found that the cancer risk from emissions from natural gas buses is 2 1/2 times greater than that from advanced clean diesel buses.”
Further undermining public understanding of the issue, the Los Angeles Times and the Associated Press reported this morning that Dr. Katherine Hammond of UC Berkeley authored the study. Hammond did not author the study. Rather, natural gas advocates wrote it from the two environmental organizations.
The study — and its interpretation by the media — fails to recognize important recent findings by the California Air Resource Board. In December of last year, the California Air Resources Board found that buying $30 million worth of Green Diesel TechnologyT buses reduces emissions by 196 tons MORE than $30 million worth of natural gas buses. It also found that you could buy nearly 100 more Green Diesel Technology buses than natural gas for the same $30 million. That means that we could retire 100 more older, polluting buses by buying Green Diesel rather than natural gas buses.
Technical notes about the NRDC methodology:
Accurate measurement of diesel exhaust is crucial to interpretation of the NRDC report. The accepted method of analysis is the NIOSH 5040 method that identifies elemental carbon which is fairly characteristic of diesel and excludes interferences from other carbon sources such as tobacco smoke, paint and other organic compounds, pollen, limestone dust, etc. The two methods used in this NRDC study are fairly indiscriminate and are not therefore accurate measures of diesel. One method measures all particles of a certain size, no matter what source they come from.
The other method used in the NRDC study measures the darkness on a strip of paper caused by various materials, mostly carbon bearing. The fact is most carbon samples contain much greater levels of non-diesel carbon materials than they do of elemental carbon from diesel. Total carbon samples may contain less than 10% diesel related elemental carbon in known exposure scenarios. The NRDC report does not fully describe the sampling methodology. It indicates that a couple of correction factors are applied to estimate the diesel content, but the factors are inaccurate. Moreover one of the factors is applied backwards and multiplies the result when it should be divided, thereby doubling the concentration reported.
