Clean air, or perhaps more precisely, environmental perfection is the killer of blue collar head-of-household jobs in the San Joaquin Valley.The 118 men and women who are about to lose their paychecks at one of Lathrop’s most high profile and longest employers — the Pilkington flat glass manufacturing facility — are the latest victims.Sixteen years ago it was 220 workers at Manteca’s Spreckels Sugar plant.In both cases, each manufacturer had spent millions of dollars complying with new air quality regulations only to have even stricter and more expensive standards thrust upon them. This time around Pilkington was forced to assess its Lathrop operations in light of a sluggish economy and a mandated $100 million upgrade in air quality equipment.Air pollution regulations per se are not the sole cause of manufacturing’s massive decline in California. There are state employment laws, the high cost of labor compared to other states, and taxes.