By Sharon Bernstein

Sept 19 (Reuters) - California on Monday moved to restrict air pollutants from sources as diverse as diesel trucks and cow flatulence, the latest of several efforts in the most populous U.S. state to reduce emissions leading to climate change.

Under a bill signed Monday by Democratic Governor Jerry Brown, the state will cut emissions of methane from dairy cows and other animals by 40 percent and black carbon from diesel trucks and other sources by 50 percent. The bill also mandates the state to reduce emissions of fluorinated gases, or hydrofluorocarbons used in refrigeration.

The measure comes on the heels of several climate-change bills signed in recent weeks by Brown, including one that by 2030 will mandate 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," Brown said at a signing ceremony in the Los Angeles suburb of Long Beach, where trucks at the nation's largest port complex spew particulate matter, including black carbon, along clogged freeways, contributing to high rates of asthma and other conditions in some of the region's poorest areas.

"It goes from some machine, into the air and into your lungs," Brown said.

The pollutants targeted in the bill signed Monday differ from carbon dioxide and other pollutants associated with global warming in that they remain in the atmosphere a relatively short time. However, these emissions have heat-trapping effects, so reducing their presence can help fight climate change, Brown said.

In addition to black carbon, which comes from trucks as well as the burning of organic material and other sources, the bill also requires reductions in hydrofluorocarbons, used in refrigeration and to power aerosol products.

It would also require the state's dairy industry, which produces 20 percent of the country's milk, to find a way to reduce methane produced by cow flatulence and manure.

One technology for doing that is known as a methane digester, which turns the gas into usable fuel. Such equipment is expensive, however, which worries the state's dairy farmers.

"This mandated 40 percent reduction in methane and 50 percent reduction in anthropogenic black carbon gas represents a direct assault on California's dairy industry and will hurt manufacturing," a small-business group, the National Federation of Independent Businesses, said in a news release.

But Brown said the mandates will lead the state to develop better technology and boost the economy. (Reporting by Sharon Bernstein)

Our Standards: The Thomson Reuters Trust Principles.