California's Diesel Emission Policy Worked as Proven by the Decrease in Air Pollution

According to a new study published today in the journal Science, applying California's strict diesel pollution requirements to the rest of the country could significantly boost the nation's air quality and health, especially in low-income communities of color.

California Diesel Emission Policy

Compared to the rest of the United States, California has exercised its jurisdiction under the federal Clean Air Act since 1990 to enforce more aggressive rules on emissions from diesel cars and engines. According to the latest report, the California Air Resources Board (CARB) policies helped the state decrease diesel pollution by 78 percent between 1990 and 2014, while diesel emissions in the rest of the United States fell by just 51 percent over the same timeframe.

According to the report, increased air pollution in California cut the annual number of diesel-related cardiopulmonary deaths in the state in half by 2014, relative to the number of deaths that would have resulted in the rest of the country took the same route. Adopting similar rules around the country could yield similar effects, particularly in areas where air pollution has had the greatest impact.

"Everyone benefits from cleaner air, but we find time and time again that lower-income populations of color are disproportionately living and working near sources of air pollution, such as freight yards, roads, and ports. The heavily exposed populations stand to lose the most as these outlets are targeted. "Megan Schwarzman, a physician and environmental health scientist at the University of California, Berkeley's School of Public Health, is the study's lead author. "It's past time, and these populations have been disproportionately harmed."

Focuses of the Study

The study also notes that exposure to delicate particulate matter (PM2.5) has been related to bad COVID-19 results, emphasizing the importance of reducing air pollution, particularly for communities of color, which are disproportionately impacted by both.

Diesel exhaust contains both dust and chemicals, and it is a significant source of PM2.5 waste around the world. PM2.5 exposure, regardless of source, will affect children's lung growth, cause airway irritation, and intensify asthma and cardiopulmonary diseases. The California Office of Environmental Health Hazard Assessment (OEHHA) has already classified diesel emissions as a human carcinogen.

"Hundreds of studies all over the world connect particulate matter toxicity to premature death," said research co-author lvaro Alvarado, a former CARB air quality expert who now works for OEHHA. "There are higher hospitalization rates for respiratory and cardiovascular conditions, as well as more emergency department admissions for asthma, in areas with higher levels of air pollution."

CARB's initiatives have gone above and above federal requirements to restrict diesel pollution from a range of mobile sources, such as heavy-duty vehicles and buses, ships and port equipment, train locomotives, and the engines that fuel building equipment and farm machinery, to increase air quality.

Pollutant Regulations

Schwarzman and colleagues cataloged the wide variety of CARB regulations that target each pollution sector in their report. They then monitored how improvements in diesel emissions interacted with the application of those laws. They then equate California's diesel pollution reductions to those in the rest of the United States to highlight CARB policies' effectiveness. According to their results, CARB's policies lowered pollution to the point that, by 2014, California was emitting less than half the diesel particulate matter that would have been anticipated if the state had followed the rest of the country's trend.

According to Schwarzman, one primary policy solution that distinguishes California is that older diesel engines must be retrofitted to meet rigorous emissions requirements. New diesel engines must meet revised emissions requirements in the rest of the United States, but older, dirtier engines can run without updates.

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