Grand Canyon National Park’s iconic views are impacted by air pollution from nearby coal-fired power plants, regional mining operations, oil and gas development, and urban/industrial emissions from both California and Mexico, as well as transportation sources, according to the National Park Service. (Pixabay)
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Aug 17, 2025
By Trimmel Gomes
A new study showed Phoenix-area vehicle emissions are significantly degrading air quality in Saguaro National Park and other protected areas, reducing scenic views and harming delicate desert ecosystems.
Called “Driving Dirty Air,” the study identified Phoenix as the nation’s second-worst vehicle pollution “hot spot” affecting national parks.
Ulla Reeves, clean air program director for the National Parks Conservation Association, said the problem stems from a mix of pollutants traveling far beyond city limits.
“It literally can travel hundreds of miles away,” Reeves pointed out. “Even though our study finds that these urban areas, with concentrated vehicle emissions is having an outsized and disproportionate impact on particular national parks, the reality is that air pollution can travel very far and wide.”
The study analyzed the Environmental Protection Agency’s 2020 National Emissions Inventory. While Arizona meets federal ozone standards, Maricopa County recorded 12 high-ozone days in 2025, down from 18 in 2020, per state data. Heavy-duty trucks account for 60% of regional NOx emissions despite fewer vehicles on the road.
Mark Rose, Sierra Nevada and senior clean air program manager for the association, noted climate change intensifies the threats.
“Pollution from vehicle tailpipes doesn’t follow park boundaries,” Rose stressed. “Much of the pollution that we see is coming from these urban areas that can be hundreds of miles away from a park, but is traveling and then impacting air quality in the national park.”
The association is urging public action against proposed federal rollbacks of clean-vehicle rules, with a comment deadline of Sept. 22.