Life is a (polluted) highway: How exposure to traffic pollution impacts health

In the United States, almost 60 million people live within 500 meters of a highway or highly trafficked road. Living near roads means greater exposure to traffic-related air pollution (TRAP) from cars and trucks, which can lead to numerous health issues, including premature death. In California, 40% of the population lives near major roads, the highest share of any state, which is why the California legislature asked the California State Policy Evidence Consortium (CalSPEC) to study the health impacts of TRAP and identify solutions.

TRAP includes vehicle exhaust fumes that contain nitrogen oxides, particulate matter, and carbon monoxide, as well as debris from brakes and tires. These toxic substances make their way into buildings, polluting the indoor air of people living nearby. Due to racist interstate citing policies in the 1960s and ’70s, major highways in the U.S. cut through well-established Black and Latino neighborhoods. As a result, communities of color are more likely to live near highways and bear the disproportionate health impacts of TRAP.

On behalf of CalSPEC, the Program on Reproductive Health and the Environment (PRHE) led a rapid “overview of reviews” of the health effects of TRAP. In an overview of reviews, researchers evaluate and summarize the findings of published systematic reviews, instead of primary studies.

Our team identified and evaluated nine systematic reviews on 26 health effects which showed that there is well-established evidence that exposure to TRAP increases the risk of mortality from poor circulatory health, poor respiratory health, lung cancer, heart disease, stroke, chronic obstructive pulmonary disease, and death due to any cause. Our analysis of the evidence also showed that exposure to TRAP has adverse effects on respiratory health (childhood asthma), cardiovascular health (heart attacks stroke, hypertensive disorders of pregnancy), reproductive health (low birth weight, preterm birth), and increases the risk of diabetes.

We conducted a secondary analysis to evaluate potential TRAP exposure disparities across demographic groups in California. Using CalEnviroScreen, a tool that can be used to map environmental, public health, and socioeconomic conditions, we found that Black, Latinx, Asian Americans and Pacific Islanders, those experiencing linguistic isolation, and those who lack health insurance, were most likely to live in areas with high TRAP.

Disproportionate rates of diseases, such as asthma and hypertension, are already seen among people of color. PRHE’s findings indicate that living in a census tract with greater exposure to TRAP could exacerbate or contribute to poor health conditions.

Based on these findings, equity and environmental justice must be key considerations in the design and implementation of policies and programs to reduce TRAP exposure.

Though air quality in the U.S. has improved since the Clean Air Act was passed in 1970, there is still work to be done to ensure more equitable access to clean air and the importance of limiting climate change and its dangerous effects.

PRHE’s research on TRAP underscores the urgent need for California legislators to enact policies that reduce harmful vehicle emissions and transition rapidly away from fossil fuels, focusing on communities most impacted. In the short term, interventions like roadside barriers and providing access to air filters that limit the amount of TRAP that gets indoors and improve indoor air quality can also be implemented. Taking steps to mitigate exposure to TRAP, especially for communities that experience disproportionate exposure, is necessary to advance public health and promote environmental justice in California.

The full CalSPEC report is available at: https://uccs.ucdavis.edu/2023-research-topic-near-roadway-indoor-air-pollution

Thank you to our fabulous partners at USC Environmental Health Centers for letting us share their fantastic infographic on TRAP pollution.

About the author

Emily Lasher is an MSPH candidate at Johns Hopkins Bloomberg School of Public Health and was an intern for the Science, Policy, and Engagement team at PRHE. She is passionate about advancing reproductive environmental health and translating science to inform policy.