"Beef: It's what for dinner," the ads say. Beef: It's also the target of an air pollution rule proposed to reduce charbroiler emissions from Bay Area restaurants. The region's nine-county pollution agency said Monday it has revamped a proposed charbroiler pollution rule so emission controls would be required only at restaurants that cook large amounts of beef. Charbroiling beef produces more fine smoke particles, a health threat to people, than grilling less fatty chicken, shrimp or vegetables, pollution managers say. "We believe we have a very good proposal that goes after the biggest pollution source from charbroilers, beef," said Jack...