AD Quality Auto 360p 720p 1080p Top articles1/5READ MOREThe Christmas Truce of 1914 proved that peace is possibleWithin Southern California, Santa Clarita had the fourth-most unhealthy days for a measuring station, 39, behind Banning Airport, 44, Perris, 54, and Crestline, 60. A complete report will be released in October. “Personal exposure to air pollution is diminishing but not at the dramatic pace that we experienced during the past two decades,” Barry Wallerstein, executive officer for the South Coast AQMD, said in a statement. While automobiles run cleaner, officials with the AQMD say trucks using diesel fuel, ships at port and trains all still contribute to unhealthy days. The AQMD is continuing to encourage the federal government to order cuts in smog-forming pollutants and fine soot in diesel exhaust from trains and ships. For the third straight year, Southern California earned the distinction as the region with the worst overall air quality in the nation, researchers from the South Coast Air Quality Management District said Thursday. Releasing preliminary findings, AQMD officials said this year’s smog season in Southern California appears to be ending with 86 days of unhealthy air at at least one measuring station. That compares to 83 days last year, and 88 days in 2004. Smog season begins on May 1 and ends on Oct. 1. The San Joaquin Valley came in a close second with 82, while Houston finished a distant third with 34 unhealthy smog days. “This trend makes it imperative that we redouble our efforts to reduce emissions, particularly from mobile security sources, in order to meet upcoming federal ozone and particulate matter standards.” It will be years before scientists can say how the nearly month-old Day Fire, which has scorched more than 150,000 acres since it started on Labor Day, has affected the air quality, officials said. Researchers say the 2006 smog season peaked early because of this summer’s unusually high temperatures. The San Fernando Valley saw triple-digit temperatures for three weeks straight in July. Smog days are measured based on standards set by the U.S. Environmental Protection Agency. An unhealthy smog day is determined when ozone levels top 0.08 parts per million during an eight-hour average. The one-hour standard is 0.12 ppm. Southern California has enacted the strictest quality requirements in the nation. The area includes Los Angeles, Orange, San Bernardino and Riverside counties. Health officials say ground-level ozone can cause shortness of breath, lung damage and increased symptoms for those with asthma and bronchitis. [email protected] (818) 713-3664160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set!