I have a new article out now in Urban Studies, which finds that—all else equal—residents of Los Angeles census tracts that generate more vehicular travel tend to be exposed to less vehicular air pollution, and that tracts with a larger non-white population proportion—whether high- or low-income—experience more air pollution than do whiter but otherwise similar tracts. There’s also a free, open access pre-print available.
Twentieth century planners designed and constructed an enormous network of expressways to open up growing American metropolises to motorists. Vast swaths of established urban neighborhoods were bulldozed to clear new channels for suburban residents to drive to job centers. Yet some older neighborhoods survived relatively unscathed.
For example, in Los Angeles, local residents organized to protest and eventually successfully cancel plans to extend State Route 2 through the affluent communities of Beverly Hills and Los Angeles’s westside. In contrast, similar grassroots efforts failed in Los Angeles’s eastside, where several major freeways carved up its less-affluent and less-white neighborhoods.
These patterns of race, wealth, and political power shaped the infrastructure planning that continues to determine regional accessibility, travel behavior, and pollution exposure today. Most studies of inequitable exposure to air pollution examine exposure differences between ethnic groups or income groups. But a better measure of injustice would ask: how much vehicular air pollution are you exposed to in relation to how much you drive?
We find that—all else equal—census tracts whose residents drive less are exposed to more vehicular air pollution. Tracts with a larger non-white population proportion—whether high- or low-income—experience more air pollution than do whiter but otherwise similar tracts. To illustrate how vehicular air pollution disparities unfold spatially, we simulate car commutes. On average, white commuters traverse tracts that are far more non-white than the tracts where most white commuters live. This disparity does not exist in the opposite direction: on average, non-white commuters do not travel through tracts that are substantially whiter than their home tracts.
Which brings us back to our earlier example of State Route 2 through Beverly Hills being canceled while Los Angeles’s eastside was carved up by freeways. Today, when white commuters traverse non-white tracts, they do so predominantly through tracts that contain highways. In other words, white commuters receive the benefits of driving on a highway, but because those highways are predominantly in non-white neighborhoods, other groups bear external costs (such as air pollution) of that driving.
Several policies can help mitigate this. First, policymakers could continue raising fuel efficiency standards for new cars and encouraging vehicular electrification. Both would reduce on-road emissions without necessarily reducing the amount of driving. However, they would not eliminate rubber tires’ and brake dust’s substantial contributions to PM2.5 pollution. Second, policymakers could enact tolls or other forms of congestion taxes to reduce total driving or capture its externalities. Third, policymakers could discourage commuting altogether by incentivizing more people to work from home, such as through tax credits. The Covid-19 pandemic witnessed a surge in remote work. Continuing these work-from-home trends after the pandemic could reduce vehicular travel and air pollution, particularly by higher-income white collar workers with more flexible jobs. Finally, policymakers can address environmental injustice through the housing market. Permitting more residential construction in job-rich neighborhoods could reduce commute distances. Further, legalizing the construction of denser and more affordable housing in less-polluted, exclusive neighborhoods could reduce exposure disparities.
Yet no single policy can eliminate longstanding systemic discrimination against low-income and non-white populations. Dismantling decades of racially-motivated transport planning and segregation requires concerted effort by planners and policymakers to redress past harms and envision a more equitable future.
From the article’s abstract:
Vehicular air pollution has created an ongoing air quality and public health crisis. Despite growing knowledge of racial injustice in exposure levels, less is known about the relationship between the production of and exposure to such pollution. This study assesses pollution burden by testing whether local populations’ vehicular air pollution exposure is proportional to how much they drive. Through a Los Angeles, California case study we examine how this relates to race, ethnicity, and socioeconomic status—and how these relationships vary across the region. We find that, all else equal, tracts whose residents drive less are exposed to more air pollution, as are tracts with a less-White population. Commuters from majority-White tracts disproportionately drive through non-White tracts, compared to the inverse. Decades of racially-motivated freeway infrastructure planning and residential segregation shape today’s disparities in who produces vehicular air pollution and who is exposed to it, but opportunities exist for urban planning and transport policy to mitigate this injustice.
For more, check out the Urban Studies article or the free, open access pre-print.