The governor of the US state of California signed a bill to restrict air pollutants from such varied sources as trucks burning diesel fuel to cow farts.  It pushes California in the lead of US states actively trying to reduce emissions that lead to climate change.

The bill signed by Democratic Governor Jerry Brown (that's right, the same guy who dated Linda Ronstadt in the 1970s) the state to reduce emissions of fluorinated gases, usually characterized as hydrofluorocarbons used in refrigeration and in aerosol products.  These are greenhouse gases that contribute to man-made global warming, and some stay in the atmosphere for centuries while others dissipate. 

But the legislation also cuts emissions of methane from dairy cows and other animals by 40 percent - the state's vast dairy industry supplies 20 percent of America's dairy products, therefore such a reduction could be substantial.  It also cuts black carbon from diesel trucks and other sources by 50 percent.  It's the latest in a series of green-themed bills passed by the California state assembly's Democratic majority and signed by Jerry Brown.  Another bill sets a 2030 deadline to achieve an overall reduction of greenhouse gas emissions to 40 percent below the level released in 1990. 

"We're protecting people's lungs, their health by cutting out a poisonous chemical that comes out of diesel trucks," said governor Brown at the signing ceremony in Long Beach, south of Los Angeles.  "It goes from some machine, into the air and into your lungs," Brown added.  The blue collar town hosts the nation's largest port complex, with a lot of truck traffic, freeways, refineries, and industry that spew particulate matter into the air, creating high rates of asthma and other conditions.