The vehicles burn more gas and emit more pollution than passenger cars, the Union of Concerned Scientists said Wednesday.
"The Big Three are the big polluters," said Roland Hwang, transportation director for the Union of Concerned Scientists. "They have the responsibility for lowering their pollution levels."
Automakers said the ranking relied too much on fuel economy, hurting companies that build larger trucks and SUVs. Under federal rules, trucks are allowed higher emissions and lower gas mileage than cars.
"I don't think it's a valid measurement of our environmental performance," Ford Motor Co. spokesman Terry Bresnihan said. "If you serve the customer because you provide trucks and SUVs they want, you're penalized in this study."
The UCS used federal emissions data and sales data to create an average level of smog-forming pollution for all cars and trucks sold in 1998 by a particular automaker. It also looked at an automaker's average fuel economy and used that to estimate the amount of greenhouse gases each car and truck fleet produced.
The worst polluter was Isuzu Motors Corp., which sells only trucks and SUVs in this country. DaimlerChrysler AG was second, Ford was third and General Motors Corp. was fourth. All four ranked above the industry average, and their results included their foreign brands.
By Justin Hyde
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