Urban neighborhoods that were redlined by federal officials in the 1930s tended to have higher levels of harmful air pollution eight decades later, a new study has found, adding to a body of evidence that reveals how racist policies in the past have contributed to inequalities across the United States today. In the wake of the Great Depression, when the federal government graded neighborhoods in hundreds of cities for real estate investment, Black and immigrant areas were typically outlined in red on maps to denote risky places to lend. Racial discrimination in housing was outlawed in 1968. But the redlining maps entrenched discriminatory practices whose effects reverberate nearly a century later. To this day, historically redlined neighborhoods are more likely to have high populations of Black, Latino and Asian residents than areas that were favorably assessed at the time. The new study's lead author, Haley M. Lane, said she was surprised to find that the differences in air pollution exposure between redlined and better-rated districts were even larger than the well-documented disparities in exposure between people of color and white Americans. "At the same time, there are so many other effects that are creating these disparities, and these delineations by redlining are just one," said Ms. Lane, a graduate student in civil and environmental engineering at the University of California, Berkeley.