In the sprawling urban expanse of Phoenix, Arizona, an astonishing fact emerges: the city’s vast pavement could blanket San Francisco four times over in a single, concentrated area. This staggering coverage—comprising roads, parking lots, and countless other paved surfaces—accounts for an estimated 40% of the city. While paving is integral to urban infrastructure, absorbing and slowly releasing heat through the urban heat island effect, the hidden health hazards lurking within this ubiquitous asphalt are garnering urgent scientific attention.
At the forefront of this emerging field is Elham Fini, a senior scientist at Arizona State University’s Julie Ann Wrigley Global Futures Laboratory. Fini’s research goes beyond the environmental footprint of pavement, focusing intently on the human health consequences of asphalt emissions. As she emphasizes, achieving true sustainability demands grappling with the tangible effects on people, not just carbon emissions or energy consumption metrics.
Asphalt’s intrinsic composition sheds light on its potential risks. Central to its structure is bitumen, a viscous petroleum byproduct that binds asphalt aggregates. Fini’s years-long investigation into why asphalt degrades so rapidly highlights volatile organic compounds—or VOCs—that are continuously emitted from bitumen. Studies published in leading scientific journals such as the Journal of Hazardous Materials and Science of the Total Environment reveal how VOC emissions not only vary throughout the day but also evolve chemically, producing ultrafine particles after sunset that degrade air quality substantially.
These carbon-based vapors are especially prevalent on hot, sunny days, linking emissions directly to climatic conditions. Immediate health effects of inhalation include dizziness and respiratory difficulties. Over longer periods, chronic exposure places individuals, especially outdoor workers such as construction crews regularly exposed to these fumes without adequate respiratory protection, at heightened risk for severe illnesses including lung cancer. This is particularly alarming given urban centers’ reliance on vast networks of asphalt infrastructure.
What compounds the threat is the dynamic nature of asphalt as it ages. Research indicates that the VOC profile changes as UV radiation and elevated temperatures accelerate bitumen breakdown. This degradation process results in the release of more toxic, and often odorless, compounds that are small enough to infiltrate human arteries and vital organs systemically. Experimental data and modeling efforts link these emissions to significant neurological impairments, with distinct vulnerability apparent in women and elderly populations.
The exacerbating role of heat cannot be understated. Rising ambient temperatures—driven by climate change and urban heat islands—intensify the emission rates of these hazardous compounds. This feedback loop presents a multifaceted environmental health challenge, especially poignant for hot, automobile-dependent cities such as Phoenix, demanding innovative mitigation strategies.
Fini’s collaborative endeavors extend into health sciences through a partnership with Dr. Bruce Johnson, focusing on the respiratory health impacts caused by asphalt emissions. Their interdisciplinary approach aims to establish evidence-based exposure limits and promote regulatory reforms to safeguard construction workers and surrounding communities from harmful VOC exposure.
Simultaneously, Fini pursues material innovation to curb toxic emissions at their source. Working with Peter Lammers of the Arizona Center for Algae Technology and Innovation, the team cultivates algae strains using nutrient-rich wastewater from municipal treatment facilities. Remarkably, this approach redirects excess nitrogen and phosphorus—pollutants in their own right—into algae biomass, creating a sustainable feedstock for asphalt binders.
When this algae-based binder is thermally processed into asphalt, it offers compelling reductions in VOC emissions, particularly the most harmful compounds. According to recent findings published in Clean Technologies and Environmental Policy, while total VOC levels remain relatively unchanged, the toxicity of emissions plummets approximately 100-fold. Moreover, algae infusion delays the deterioration of pavement integrity, extending lifespan and potentially lowering long-term construction and maintenance costs.
Beyond algae, Fini explores other binder alternatives, such as bio-derived materials extracted from forest thinning byproducts. This multifaceted research agenda not only targets environmental sustainability but also aligns with public health priorities. Practical implementation is underway, with plans to pave roadways in Phoenix using algae-infused asphalt, enabling real-world performance assessments of emissions and durability.
This emerging awareness that infrastructure materials could and should serve dual purposes—functionality and public health improvement—is groundbreaking. Considering the United States boasts over four million miles of roads, the potential impacts are profound. Transforming these veins of urban life into vectors of health promotion rather than environmental harm mirrors a paradigm shift in engineering and material science, one that integrates ecological, technological, and human health perspectives.
The implications for communities, policymakers, construction industries, and scientists are manifold. Crucially, integrating VOC emission profiles into air quality modeling frameworks must become standard practice to capture previously overlooked pollution sources. Concurrently, prioritizing innovation in sustainable binders can significantly contribute to global climate and health targets.
Elham Fini’s research epitomizes the convergence of environmental engineering, toxicology, and urban planning, underscoring the imperative that sustainability encompasses human well-being. As cities like Phoenix navigate the challenges of a warming planet and expanding urban footprints, reimagining asphalt’s role could revolutionize not only infrastructure longevity but also public health outcomes on a massive scale.
Subject of Research: Not applicable
Article Title: Humidity: A hidden driver of toxic emissions and asphalt decay in a changing climate
News Publication Date: 10-Apr-2026
Web References:
– https://www.sciencedirect.com/science/article/pii/S0304389426006916
– https://www.sciencedirect.com/science/article/pii/S0048969726003931?dgcid=author
– https://19january2017snapshot.epa.gov/heat-islands/heat-island-impacts_.html
– https://pubmed.ncbi.nlm.nih.gov/39724706/
– https://link.springer.com/article/10.1007/s10098-026-03482-z
References:
– Journal of Hazardous Materials
– Science of The Total Environment
– Clean Technologies and Environmental Policy
Image Credits: Joanna Allhands
Keywords
Applied sciences and engineering, Environmental engineering, Public health, Materials science
