SAN FRANCISCO (Reuters) – California on Friday became the first state in the country to force big diesel trucks to clean up their exhaust, despite warnings from truckers the new rules will force them out of business. About a million vehicles, from big rigs to school buses, are affected by the new rules, which will begin taking effect in 2011 and do not require further ratification. Some vehicles will have to start retrofitting engines in 2011 and some older trucks will be forced into retirement starting in 2012. By 2023, all trucks must meet 2010 new engine emission standards. The...