Seems some carriers at the Southern California ports have found a loophole that allows them to continue operating some older, higher-polluting trucks that supposedly have been banned from the ports as part of their Clean Truck programs.

According to an article this week in the Los Angeles Business Journal, the rules only apply to three-axle Class 8 tractors. Class 7 two-axle tractors aren't covered. So some carriers are using the lighter rigs to return empty containers.

The Clean Air Program requires all Class 8 trucks doing business in the ports to meet 2007 federal emissions standards by 2012.

Since January, the paper reports, the number of Class 7 trucks registered to work at the Port of Los Angeles has jumped from 28 to more than 500. At the Port of Long Beach they've gone from 28 to 480.

"Some companies claim that being able to use the cheaper trucks is the only thing that's keeping them in business," the paper reports. "While new emissions-compliant Class 8 trucks sell for $100,000 or more, they say, older Class 7 trucks cost about one-tenth that price. While insuring, maintaining and licensing the new trucks can run $1,400 a month, operating the lighter trucks costs about 25 percent less."

The ports are waiting for action by the California Air Resources Board, which is set to discuss the matter Dec. 16, the paper says. The board will consider a recommendation that state emission standards be amended to include Class 7 trucks.