A Sunscreen for Pavement Could Help Keep Cities Cool

A Sunscreen for Pavement Could Help Keep Cities Cool
Photo: Alex Wong, Getty Images

The heat dome baking vast swaths of the U.S. and Canada has put the dangers of extreme heat on display. It points to the need for urgent adaptation so that cities don’t overheat, and that means reducing the urban heat island. Absent planting more trees, there may be other solutions to help keep cities cooler as the climate crisis worsens.

Pavement Technology Inc. created a spray-on treatment for pavement, called A.R.A.-1 Ti, which it says can lower its temperature. Developed in collaboration with Louisiana State University researchers, the spray’s exact makeup is a trade secret, but it’s based on titanium oxide, a compound used in many sunscreens, white paints, and pharmaceuticals. Titanium dioxide is a photocatalyst, meaning ultraviolet rays activate the compound’s electrons, which absorb and disperse light and heat.

Marketed as a “road rejuvenator,” the Ohio-based firm says the substance can also “revitalize ageing asphalt” by making it stronger, a property that could come in pretty hand, too. This week, roads across the West have been cracking and buckling in the extreme heat.

As if that’s not enough, the spray is also meant to dissolve car exhaust pollution, including nitrogen oxide and volatile organic compounds. Through a chemical process called photocatalysis, titanium dioxide creates energised electrons that break down toxins in the air. In a promotional video, the company claims that 1.6 kilometres of sprayed pavement can have the same air quality benefits as planting 8 hectares of trees.

The company has done its own research that it says confirms all these properties. Municipalities including Orlando, Charlotte, Raleigh, Greenville, and Charleston are putting the spray to the test. As they do so, Pavement Technology is cutting up samples of asphalt from treated areas along with gathering air quality and weather data, and then sending them off to researchers at Texas A&M University to collect data on how well it works.

Last year, Orlando International Airport in Florida used the treatment, and the researchers found it cut nitrogen oxide pollution essentially in half. Officials from Charleston County, South Carolina are hoping to see similar results.

In Charleston, the public works department is specifically using the treatment on roads in two neighbourhoods, Union Heights and Rosemont, which are both full of asphalt and located next to major highways. Both neighbourhoods are also epicenters for the heat island effect that occurs in heavily built up areas. Buildings and pavement can absorb the sun’s rays and radiate heat, leaving these areas up to 4.4 degrees Celsius hotter than areas with more trees and greenery nearby. The worst heat islands are predominantly concentrated in low-income areas and locations home to people of colour. Have a solution like this to help cool things down could have major public health benefits and save people money on cooling costs.

This all sounds very exciting, but technologies like this should be no replacement for comprehensive climate justice policy. To really keep cities safe from rising temperatures, we still have to do the hard work of dismantling the fossil fuel industry and reducing carbon pollution ASAP. Even if this technology works to cool down heat islands, it’s not the only solution we can rely on. After all, adding trees and green space to neighbourhoods doesn’t just lower temperatures, it can also have benefits for mental health and make outdoor spaces more welcoming for people to congregate. More natural space in cities can also help soak up rainfall rather than letting it runoff and cause flooding. Special pavement coatings are cool and all, but we can’t forget the big picture.