In one of the most comprehensive studies to date, the South Coast Air Quality Management District is testing emission control devices that may significantly reduce cancer-causing soot from diesel school buses.
"School children and school workers are exposed to cancer-causing diesel fumes every day at ground level," said William A. Burke, AQMD Governing Board Chairman. "These new devices may offer a cost-effective way to reduce their cancer risk."
Tests on 39 buses operating in the Los Angeles, Anaheim Union High School and Hemet unified districts started this fall and should be complete by next summer.
The buses are equipped with particle traps that can reduce microscopic particles, or soot, by 80% or more. They must use low-sulfur diesel fuel, containing no more than 15 parts per million of sulfur. Diesel sold in California today contains an average of 120 ppm of sulfur, which would reduce the efficiency of the particle traps if used with them.
The particle traps, installed in the bus exhaust system at the muffler, are being provided by three manufacturers: Johnson Matthey of Wayne, Penn., Engelhard of Iselin, N.J., and Ceryx Inc. of Santa Paula. The traps cost $5,000 to $8,000 each.
Of the 39 buses, 26 will be retrofitted with particle traps and 13 will use only low-sulfur fuel for comparison. The test program is unique in that it includes a wide range of school buses and engines ranging from model years 1977 to 2000.
Durability Test
In a related test, AQMD will test the durability of the catalysts -- key to continued emissions reductions -- by driving two of the retrofitted buses up to 50,000 miles each. The two buses will be driven continuously over regular routes in Anaheim Union High School and Los Angeles Unified districts.
The total cost of the retrofit and durability tests is $693,200. AQMD is contributing $451,100 and the remainder will be contributed by the California Air Resources Board and the particulate trap manufacturers.
AQMD is the air pollution control agency for Orange County and the urban portions of Los Angeles, San Bernardino and Riverside counties.
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AQMD Home Page
This page updated: March 01, 2004
URL: http://www.aqmd.gov/news1/School_Bus_Test.htm