Jeremy Axworthy, a researcher at the Center for Marine Debris Research (CMDR) at Hawaiʻi Pacific University, presented the findings at the spring meeting of the American Chemical Society (ACS).

“This work investigates whether it’s responsible to use recycled plastics in Hawaii’s roads,” shares Axworthy. “By reusing plastic waste that is already in Hawaii, we can reduce the environmental and economic impacts of transporting waste plastics from the islands, incinerating it or dumping it in Hawaii’s overflowing landfills.”

Why Hawaii Is Testing Recycled Plastic Roads

Since 2020, most roads in Hawaii have been built using polymer-modified asphalt (PMA), which is designed to improve strength and durability. Compared with conventional asphalt, PMA is more flexible and better able to resist cracking, rutting, and water damage, making it well suited to Hawaii’s tropical climate.

To make PMA, pellets of styrene-butadiene-styrene (SBS; a type of copolymer) are melted into a sticky petroleum-based asphalt binder. That binder is then mixed with heated aggregates (rocks and sand), coating the material before it is laid as pavement.

Researchers wondered whether some of the virgin polymer could be replaced with discarded plastics. They also wanted to know whether roads made with recycled plastics would perform well and whether they might release microplastics or other chemicals into the environment. Those questions led the Hawaii Department of Transportation (HDOT) to partner with environmental chemist Jennifer Lynch, director of CMDR and leader of the research team.

Recycling Fishing Nets Into Asphalt

HDOT asked Lynch’s team to tackle two key tasks. The first was to supply abandoned fishing nets collected from Hawaii’s waters for use in experimental recycled plastic asphalt.

“Foreign plastic derelict fishing gear is the largest contributor of Hawaii’s marine debris problem,” shares Lynch. “To date, CMDR’s Bounty Project, which pays a financial reward to licensed commercial fishers for marine debris removal, has removed 84 tons of large, derelict fishing gear from the Pacific Ocean.”

The second goal was to determine whether pavement made with recycled plastic released more microplastics than standard SBS-modified asphalt.

“CMDR’s laboratory is equipped with state-of-the-art chemical instrumentation for quantifying and characterizing microplastics in environmental samples,” explains Lynch. “This capability is incredibly unique and impactful, especially when coupled to our marine debris-removal project and our mission to recycle the debris into long-term, locally necessary infrastructure products.”

After a U.S. company processed the recovered plastics into materials suitable for asphalt production, HDOT moved the project into the real world. A local paving company resurfaced sections of a residential street on Oahu using three different asphalt mixtures: one with standard SBS, one containing recycled polyethylene from Honolulu’s residential recycling program, and one made with polyethylene recovered from discarded fishing nets.

About 11 months later, Lynch’s team returned to collect road dust from each section so they could measure any microplastic released into the surrounding environment.

Measuring Microplastic Shedding

The scientists separated different types of polymers from the road dust, including microplastics, larger plastic fragments, and tire rubber. They then used pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) to determine where the materials came from. The analysis identified styrene and butadiene from standard PMA, polyethylene from recycled plastic and fishing net pavements, and isoprene and butadiene rubber from vehicle tires.

Early findings showed that pavement containing recycled polyethylene did not release more polymers than conventional SBS pavement. The same pattern appeared in laboratory performance testing and in simulated stormwater collected from the experimental road sections.

Although researchers detected microplastic-sized particles, only a very small number were identified as polyethylene, regardless of which pavement type they came from. The researchers believe this is because the plastic becomes blended into the asphalt binder. As the road wears over time, the particles that break away are made up of rock, asphalt binder, and polymer together rather than plastic by itself.

The team is also comparing polymer release from the pavement with the amount of tire material found in road dust.

“In our initial Py-GC-MS data,” continues Lynch, “we saw tire wear swamps the signal of polyethylene by orders of magnitude, like gigantic peaks! We had to search the weeds of the chromatogram to find signs of polyethylene.”

A Possible New Future for Plastic Waste

More testing is still needed to evaluate how well these recycled plastic roads hold up over the long term. Even so, the researchers believe the approach could eventually reduce both landfill waste and marine debris across Hawaii.

“Some people think plastic recycling is a hoax — that it doesn’t work; it’s too challenging,” Lynch shares. “But this work demonstrates that recycling can work when society prioritizes sustainability.”

The research was funded by the Hawaii Department of Transportation.

Meeting

ACS Spring 2026

Title

Harvesting ocean plastics to pave hawaiian roads: Evaluation of microplastic and plastic additive release from asphalt incorporating recycled plastic from various waste streams

Abstract

Polymer modified asphalt (PMA) is used to increase strength and durability of roads. In Hawaii, PMA is typically produced using the virgin co-polymer styrene-butadiene-styrene (SBS). Recycled plastics, such as high-density polyethylene (HDPE), may also be added to asphalt serving to sequester plastic waste. In the state of Hawaii, derelict fishing gear (DFG) is a significant problem, yet it is also a source of HDPE that can be used in recycling. However, asphalt performance and the consequences of adding recycled polymers to asphalt are not well understood. In collaboration with the Hawaii Department of Transportation (HDOT) and the University of Hawaii (UH), the Center for Marine Debris Research (CMDR) are testing the feasibility of using recycled HDPE in asphalt by quantifying microplastics and plastic additives release from roads paved with asphalts made from different combinations of virgin and recycled polymers. The specific asphalt combinations being tested are: SBS (Control-PMA), DFG with and without SBS (DFG-PMA and DFG-neat), Local Waste recycled HDPE with and without SBS (LW-PMA and LW-neat), and Commercially Available, post-industrial recycled HDPE with and without SBS (CA-PMA and CA-neat). Microplastic and plastic additive release under laboratory conditions were performed using a Hamburg Wheel Tracker Test (HWTT) with water sample analyses. Field trials were conducted on a residential road on the island of Oahu, Hawaii. Road dust was swept and analyzed for microplastics by direct analysis and solvent extraction to separate bound plastic from asphalt and plastic additives by water extraction. Microplastic samples utilized pyrolysis gas chromatography mass spectrometry for analysis. Plastic additives are subjected to solid phase extraction with analysis by gas chromatography mass spectrometry. Results produced using these novel analytical methods provide guidance on the use of recycled plastics over virgin plastics in roadways. Moreover, results of this study may provide a viable end of life fate for plastic marine debris, leading to cleaner and healthier oceans.

Scientists have long known that body composition changes with age, but exactly why fat tends to accumulate around the midsection has remained unclear.

Now, researchers at City of Hope have identified what may be a key biological driver of age-related belly fat. Their findings, published in the journal Science, point to a newly identified type of stem cell that appears during aging and may help fuel the production of new fat cells. The discovery could eventually lead to new strategies for reducing abdominal fat and promoting healthier aging.

“People often lose muscle and gain body fat as they age — even when their body weight remains the same,” said Qiong (Annabel) Wang, Ph.D., the study’s co-corresponding author and an associate professor of molecular and cellular endocrinology at City of Hope’s Arthur Riggs Diabetes & Metabolism Research Institute, a leading center for diabetes research. “We discovered aging triggers the arrival of a new type of adult stem cell and enhances the body’s massive production of new fat cells, especially around the belly.”

Looking Beyond Enlarged Fat Cells

The research team worked with scientists at UCLA and conducted a series of experiments in mice that were later supported by studies of human cells.

Their investigation focused on white adipose tissue (WAT), the body’s primary fat-storage tissue. White adipose tissue is responsible for storing excess energy and is a major contributor to weight gain and belly fat accumulation.

Scientists have long known that existing fat cells can become larger as people age. However, the researchers suspected that another process might also be contributing to expanding waistlines: the creation of entirely new fat cells.

If true, that would mean aging fat tissue could continue growing not just by enlarging existing cells, but by constantly adding new ones.

To test this idea, the team studied adipocyte progenitor cells (APCs), a type of stem cell found within fat tissue. These cells serve as precursors that can mature into fully developed fat cells.

Older Stem Cells Produced Far More Fat

The researchers transplanted APCs from both young and older mice into a separate group of young mice.

The results were striking. APCs taken from older animals generated large numbers of new fat cells.

The opposite experiment produced a very different outcome. When APCs from young mice were transplanted into older mice, they generated relatively few new fat cells.

This suggested that the ability to aggressively produce fat was built into the older APCs themselves and did not depend on the age of the animal receiving them.

To understand what was happening at a molecular level, the researchers used single-cell RNA sequencing, a technique that allows scientists to examine gene activity in individual cells.

The analysis revealed that APCs were relatively quiet in young mice. In middle-aged mice, however, these cells became highly active and began producing large numbers of new fat cells.

“While most adult stem cells’ capacity to grow wanes with age, the opposite holds true with APCs — aging unlocks these cells’ power to evolve and spread,” said Adolfo Garcia-Ocana, Ph.D., the Ruth B. & Robert K. Lanman Endowed Chair in Gene Regulation & Drug Discovery Research and chair of the Department of Molecular & Cellular Endocrinology at City of Hope. “This is the first evidence that our bellies expand with age due to the APCs’ high output of new fat cells.”

Discovery of a New Age-Related Stem Cell

The scientists found that aging did more than simply activate APCs.

As mice reached middle age, some APCs transformed into a newly identified stem cell population called committed preadipocytes, age-specific (CP-As).

These cells appeared specifically during aging and proved especially effective at producing new fat cells. Their emergence may help explain why older mice gained more fat as they aged.

The researchers then searched for the biological signals controlling this process.

They identified an important signaling pathway known as leukemia inhibitory factor receptor (LIFR). Signaling pathways are communication systems that allow cells to receive instructions and coordinate their behavior. In this case, LIFR appeared to play a major role in helping CP-A cells multiply and develop into fat cells.

“We discovered that the body’s fat-making process is driven by LIFR. While young mice don’t require this signal to make fat, older mice do,” explained Wang. “Our research indicates that LIFR plays a crucial role in triggering CP-As to create new fat cells and expand belly fat in older mice.”

Similar Fat-Producing Cells Found in Humans

To determine whether the findings might apply beyond mice, the team analyzed human tissue samples from people of different ages using the same single-cell RNA sequencing approach.

The researchers identified cells that closely resembled the newly discovered CP-As. These cells were found in greater numbers in tissue from middle-aged individuals.

The human CP-As also showed a strong ability to generate new fat cells, suggesting that a similar biological process may occur in people.

“Our findings highlight the importance of controlling new fat-cell formation to address age-related obesity,” said Wang. “Understanding the role of CP-As in metabolic disorders and how these cells emerge during aging could lead to new medical solutions for reducing belly fat and improving health and longevity.”

A Potential New Target for Age-Related Obesity

Although more research is needed, the discovery provides scientists with a promising new target for future therapies.

Researchers now plan to track CP-A cells in animal studies, investigate how these cells behave in humans, and explore ways to block or eliminate them. If successful, such approaches could potentially help prevent the accumulation of belly fat that commonly accompanies aging.

The study’s first authors were City of Hope researcher Guan Wang, Ph.D., and UCLA researcher Gaoyan Li, Ph.D.