Welcome to The Hill’s Sustainability newsletter, I’m Sharon Udasin — every week we follow the latest moves in the growing battle over sustainability in the U.S. and around the world.

Communities of color in California have seen significant improvements in air quality levels in recent years, but they are still exposed to pollutants at much higher rates than white individuals, a new study has found.  

Dramatic declines: Californians across the board are inhaling far fewer contaminants from vehicle emissions than they were 25 years ago, according to the study, published in Science Advances on Wednesday.  

• Exposure to fine particulate matter (PM 2.5) from cars, trucks and other automobiles has plunged by 65 percent.
• Over the past two decades, the biggest reductions in air pollution levels have occurred in Black, Hispanic and Asian communities. 

Exposure inequalities: Nonetheless, stark differences in exposure rates remain, warned the authors, from the University of California Berkeley, California’s Office of Environmental Health Hazard Assessment and the University of Washington. 

“Systemic inequality in terms of relative exposure disparity can persist even if the most overburdened areas receive the largest reductions in exposure in absolute terms,” they stated.  

Decreases statewide: The scientists developed a model to estimate total PM 2.5 levels that resulted from California vehicular emissions from 2000 to 2019 — differentiating the data by racial group and calculating population-weighted averages. 

• For Black Californians, exposure levels dropped from about 3.5 to 1.2 micrograms per cubic meter.
• For Hispanic Californians, from 3.5 to 1.3 micrograms per cubic meter.
• For Asian Californians, from 3.3 to 1.2 micrograms per cubic meter.
• For white Californians, from 2.7 to 0.9 micrograms per cubic meter.  

Demographic disparities: For each demographic group, the scientists then computed the relative difference between their average pollution levels versus that of the overall state population. 

• They found that the relative disparity for Hispanic Californians increased from 12 percent in 2000 to 13.9 percent in 2019.
• Black and Asian Californians also experienced similar increases: 10.5 to 11.5 percent and 5.4 to 6.2 percent, respectively.  

But for white Californians, the relative disparity in exposure decreased from negative 13.5 to negative 15.5 percent, per the study. 

Shifting priorities: In light of their findings, the researchers stressed a need for policy approaches that prioritize populations most impacted by air pollution exposure.  

• They acknowledged that California is already addressing this challenge to some extent, with certain equity-driven, community-focused initiatives.
• Regulations and incentive programs are helping accelerate zero-emission vehicle deployment in lower-income areas, the authors added.  

“When we find that disparities persist, they persist in a larger story of environmental inequity in California,” they concluded.