Arizona State University Scientists Link Aging Urban Asphalt to Toxic Vapor Emissions and Neurological Damage Risks

ASU researchers find that aging asphalt releases toxic VOCs linked to lung cancer and neurological damage, especially in extreme heat.

By: AXL Media

Published: Apr 22, 2026, 4:16 AM EDT

Source: Information for this report was sourced from Arizona State University

The Hidden Chemical Footprint of Urban Infrastructure

In car-centric metropolitan areas like Phoenix, pavement covers approximately 40% of the land area, creating a massive reservoir for heat and chemical activity. While the "urban heat island" effect is a well-documented energy concern, senior scientist Elham Fini of ASU’s Global Futures Laboratory argues that the human health impact of asphalt is equally critical. Asphalt is held together by bitumen, a sticky petroleum byproduct that releases volatile organic compounds (VOCs). Recent findings published in the Journal of Hazardous Materials and Science of the Total Environment demonstrate that these carbon-based vapors transform into ultrafine particles after sunset, significantly degrading local air quality and posing immediate risks such as dizziness and respiratory distress.

The Toxicity of Degrading Roadways

A concerning aspect of the research is that asphalt does not become inert as it ages. Instead, the breakdown of bitumen under intense sunlight and high temperatures leads to the release of different, more hazardous strains of VOCs. Unlike the characteristic scent of fresh asphalt, these aging-related emissions are often odorless but small enough to penetrate human arteries and vital organs. Modeling analysis suggests these specific toxins can cause substantial neurological damage, with the most significant impacts observed among the elderly and women. Professor Fini emphasizes that rising global temperatures are exacerbating these emissions, turning vast stretches of roadway into active sources of toxic exposure.

Occupational Hazards and Long-term Health Risks

The health implications are particularly dire for construction and road-maintenance workers. Long-term exposure to bitumen fumes without the use of respirators has been linked to an elevated risk of lung cancer. To address this, Fini is collaborating with Dr. Bruce Johnson through a partnership with the Mayo Clinic to quantify the exact levels of VOC exposure that trigger unsafe respiratory responses. The ultimate goal of this collaboration is to establish stronger regulatory protections for workers and to develop a data-driven foundation for lower-emitting asphalt formulations that protect both the labor force and the communities living adjacent to major thoroughfares.