DIAMOND BAR, CA — Companies that provide trash trucks, street sweepers, and school buses for public agencies will have to buy the cleanest-burning vehicles available under rules being rein-stated by the region’s smog-fighting agency, reported the San Bernardino Sun. Following a five-year legal battle that raised all the way to the U.S. Supreme Court, a federal district judge ruled against an attempt by the Engine Manufacturers Association and the Western States Petroleum Association to invalidate the rules in their entirety. In the wake of that decision, the Air Quality Management District (AQMD) plans to start enforcing the rules again on Monday. Pollution from diesel is one of the most dangerous components of smog, especially because of the ultra-fine particles that can burrow deep into lungs and other organs. The rules are expected to pull nearly 5,000 tons per year of pollutants from the air and are targeted mainly at diesel-powered vehicles, though taxicabs that operate at airports also are included. Companies that work for the federal government or that do not operate under contract to a state or local agency are not affected. The Engine Manufacturers Association strongly disagreed with the decision in May and plans to appeal the ruling.