California's air pollution control standards have drastically dropped the amount of diesel particulate matter in the air, and cardiopulmonary deaths attributable to air quality.

Scientists at UC Berkeley are hailing the state's diesel engine standards and other measures imposed over a number of years, even in the face of loosened environmental regulations in recent years.

If one has never seen the pictures of the city of Los Angeles before the Clean Air Act, they look like something out of the movie Escape from L.A. But encouraging shifts away from high-sulfur fuels, and replacements of diesel ships with electric ones, has gradually scaled the horror show back—despite the fact that still today there are more cars registered in the state of California than any other state.

"Our analysis of mobile-source DPM (diesel particulate matter) emissions suggests that many California sector-based policies have been highly effective relative to the rest of the US," write the authors of the paper published in Science.

They found that from the period between 1990 and 2014, the amount of DPM in the California skies fell by 78%, while cardiopulmonary and cancer deaths linked to diesel pollution dropped by 82%.

The largest fall came from tractor-trailers, which is unsurprising given the fact they often run on diesel and cover many miles. Reductions were also observed in passenger and construction vehicles, as well as from the marine sector.

California's overall consumption of diesel actually increased over this period, which suggests that mandates to move to more refined fuels and retrofitting existing vehicles with pollution filters are highly effective strategies (both are recommended for implementation in other states by the Berkeley scientists).

Moves towards electric public and private transportation, such as Governor Newsom's executive order to ban the sale of fossil fuel vehicles beyond 2035, should clear California's skies substantially more—and will be a momentous accomplishment from one of the country's largest economies.

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