For the second year in a row, no first-stage ozone pollution alerts were reported in the greater Los Angles area last year. Many of the 16 million people who live in the four-county area are now breathing air that meets all of the U.S. EPA health standards. Unhealthful days have dropped 75 percent over the last 15 years, despite surges in the number of people and cars in the region. The improvements came about because tough air quality regulations led to the development of cleaner cars, consumer products, power plants, and factories. But even the newest gee-whiz technology may have a hard time keeping up with future population growth — 6.7 million more people are expected to settle in the L.A. area over the next two decades.