Air-quality regulators in California have introduced tough new rules controlling fuel emissions from some diesel-powered engines.
The regulations will affect off-road vehicles such as bulldozers and airport baggage trucks.
In all, about 180,000 vehicles will have to be replaced or updated under the toughest rules in the US.
The new rules require diesel equipment to be cleaned up from 2010, but the process will probably take until 2025.
The California Air Resources Board voted unanimously to clean up emissions from vehicles like bulldozers, fork-lift trucks and snowcats which are used on ski resorts.
The rules will eventually force the oldest and most polluting equipment out of service.
Construction firms will have to spend billions of dollars on new vehicles or on refitting engines.
Officials have acknowledged that coming up with a proposal that is both cost-effective and fair has not been easy.
The clean-air plan has been promoted by health advocates and has been the focus of intense lobbying by industry representatives, who were concerned about the cost to businesses.
California Governor Arnold Schwarzenegger said the Board's action showed that California was "leading the charge" to protect public health.
He added that the new regulations would prevent thousands of premature deaths every year and save billions in health-care costs.
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