Los Angeles frequently had `` Stage 3 '' smog alerts when I was a kid , meaning that we were n't supposed to play outside . Fortunately , those days are over . Air quality in California , including Los Angeles , has vastly improved from decades ago . But compared to other states and to the Federal Clean Air Act health standards , California is way behind on cleaning up its air pollution . The American Lung Association ( ALA ) just released its annual `` State Of The Air '' report listing the most polluted cities in the United States . Of the seven worst cities ranked as having the worst air quality , six -- including Los Angeles - are in California , despite the state having the toughest regulations in the country . Why is this ? The two biggest air pollution culprits are transportation sources such as cars and trucks and stationary sources such as oil refineries and industrial facilities . The ALA rankings look at two different pollutants : ozone ( smog ) and fine particulate matter . Ground-level ozone is formed when nitrogen oxides and volatile organic compounds `` cook '' in sunlight to produce ozone . This mix of chemicals largely stems from the burning of fossil fuels : the pollution that comes from our power plants and industrial facilities and from the exhaust pipes of our cars , trucks , ships and trains . The ozone smog that comes from this chemical stew burns the eyes , makes breathing painful and can cause chest pain , coughing , throat irritation and can worsen asthma . Children are at greatest risk from exposure because their lungs are still developing , and they are more likely to be active outdoors when ozone levels are high . Rising temperatures from climate change will only serve to spur even more of this pollution . Particulate matter , the other major air pollutant in cities , is often smaller than the diameter of a human hair . Just like ozone , fossil fuel combustion at power plants and by cars and trucks plays a major role in its production . The very small particles can lodge deep in the lungs , causing health risks such as premature death in people with heart or lung disease , asthma aggravation and decreased lung function . Children and seniors are at the greatest risk from particulate pollution . And we 're seeing these human health impacts all across Southern California and the Central Valley . If you 've been to L.A. , you know how bad the traffic is -- it can take me 2 hours to drive the 18 miles from my office to Dodger Stadium . All those vehicles contribute to Southern California 's horrible air pollution . It 's true that cars now emit fewer pollutants -- due to regulation at the federal and state level -- but Los Angeles simply has too many cars for the carrying capacity of the region . A massive increase in public transit , hybrid and zero-emission cars and trucks is a sound solution to help alleviate this pollution . The intense truck traffic on L.A. 's freeways is a symptom of the L.A. area ports ' successes . Over 80 % of all U.S. imports from Asia come through these ports , and roughly 40 % of those imports are moved by diesel trucks . California state air regulators have taken strong steps to clean up the diesel truck fleet , but we are far from where we need to be -- diesel trucks , collectively , are still an enormous source of particulate pollution . Another solution is replacing fossil-fueled trucks that haul cargo containers to and from Los Angeles ' ports with zero-emission freight movement systems such as electric trucks . Ports and regulators have already spent many millions of dollars developing these sensible 21st century systems , but industry has yet to deploy them . The San Joaquin Valley , California 's other pollution center , is largely a rural area and home to the state 's agricultural industry . The wide , flat valley , like Los Angeles , is surrounded by mountains that trap air . Since the valley 's population is growing , there are also more cars and trucks . And two major north-south truck routes , I-5 and U.S. 99 , bisect the valley . Off-road vehicles used in agriculture as well as agricultural practices such as burning off fields also contribute to particulate matter overload . I drove through the valley on my way to Yosemite National Park last October , but the smog was so thick I could n't see the Sierra Nevada range until I was there . Bottom line : too many cars and trucks , and too much fossil fuel combustion by vehicles , power plants and industry are the problem . And climate change is only making it worse . But there 's hope : California leads the movement towards a clean , renewable energy future , and if we can accelerate that transition , we have a fighting chance of getting off the ALA 's `` worst '' list .
A new report lists the most polluted areas in the country , including several major cities . # ##off : There are too many cars and trucks , oil , and industrial facilities . He says Los Angeles , for example , needs to massively expand its public transit system . Pettit : California needs to accelerate development of clean , renewable energy .