When you think about what causes air pollution in California, cars and factories probably come to mind. But what about ports? For instance, the Port of Los Angeles and the neighboring Port of Long Beach, when combined, are the single largest source of pollution in Southern California. But change is afoot. Reporter: Saul Gonzalez, The California Report Earlier this month, thousands of employees were laid-off off by one of the country’s largest stone fruit producers, which operates in central California. The Prima Wawona layoffs are part of a decades-long shift in farm work. Reporter: Kerry Klein, KVPR Learn more about your ad choices. Visit megaphone.fm/adchoices