Nick Lubecki has been an urban farmer in Pittsburgh for the last 15 years. The heat has noticeably intensified over that time, with back-to-back summers of sweltering temperatures affecting when he harvests produce at Braddock Farm, a small urban plot nestled next to an operating steel mill that grows vegetables like lettuce, collards, and tomatoes. His current strategy for beating the brutal heat: a wide brim hat and plenty of water. Lately, farming consistently throughout the day has been “significantly more exhausting,” he said. “It’s really hard to keep going.”
Summers are getting hotter everywhere, and that is especially true in cities including Pittsburgh, which this year has seen more than four times the number of days over 90 degrees Fahrenheit than it does in a typical year. That’s due in part to the urban heat island effect, in which a city’s infrastructure traps heat, making it hotter than in neighboring suburbs. To combat the growing health risks for outdoor workers like Lubecki, scientists and designers are developing a slate of new fabrics to counteract extreme heat. But worker-safety specialists and labor advocates are concerned that commercializing wearable technologies—even with the best of intentions—may end up aggravating existing issues with worker exploitation.
To cope with climate change and stay healthy outside, humans need adaptations, and heat-reflecting textiles have the potential to play a crucial role. Such solutions are “super important to not only show that there’s some really cool technology that’s resulting from this need,” said Enrique Huerta, legislative director at Climate Resolve, a nonprofit that advocates for equitable climate solutions, but also that there is “a need to deploy it responsibly. That’s really, really important to highlight.”
What makes the urban heat island effect so dangerous is its cumulative nature. During the day, the built environment—concrete, asphalt, brick—readily absorbs the sun’s energy. At night, a city slowly releases all that built-up heat, keeping temperatures extra-high into the morning. If you don’t have air conditioning and your body can’t cool down at night, and a heat wave continues day after day, the stress builds and builds. Nellie Brown, director of Workplace Health and Safety Programs at Cornell University, says that workers exposed to such conditions without relief are vulnerable to illnesses like heatstroke, but can, in extreme cases, experience serious brain damage, kidney failure, and even death.
In a recent report, Climate Central, a nonprofit that communicates climate science, studied the urban heat island index, or UHI, in 65 large U.S. cities to calculate how much the built environment boosts temperatures. “The other major component . . . is population density, because we as people create a lot of waste heat with our activities,” said Jennifer Brady, senior data analyst at Climate Central. “So cars, buses, trucks can create waste heat.” Of the 50 million people included in Climate Central’s analysis, 68% lived in areas with a UHI of 8 degrees or higher.
Lower-income neighborhoods also tend to be zoned for more industrial activities, with less trees and more asphalt and large buildings, all of which absorb and then radiate heat. That’s especially perilous if those workers live and sleep in high-UHI neighborhoods elsewhere, and they’re coming to work after a night of still-sweltering temperatures. This is where a fabric that can alleviate some of the physical symptoms of heat on the body could end up serving as a lifeline.
Special textiles exist already to help cool a wearer by scattering direct sunlight away from the body or by emitting infrared radiation—which would be handy when you’re out on a hike or, say, working in a backyard garden. A legion of U.S. apparel companies manufacture clothing that helps mitigate the heat from direct sunlight, but those fabrics aren’t designed to offset the oppressive heat that gets trapped in cityscapes. In a city, the built environment radiates heat from below, too, presenting an additional engineering challenge.
In June, researchers presented a clever new textile design that can indeed counter the urban heat island effect. The top layer is made of plastic polymethylpentene, or PMP, fibers, which let in heat radiating from roads and buildings. Underneath that layer is silver nanowire, which is very good at reflecting that heat back through the PMP fibers and away from the body. Below that, against the skin, is a layer of wool that acts as a buffer.
“It provides very good mechanical support, because those PMP and silver nanowires are extremely thin,” said University of Chicago materials scientist Po-Chun Hsu, coauthor of the new study. Like a plain white shirt helps bounce some of the sun’s energy away from the body, this new textile can deflect the heat that comes from below, like from asphalt and city sidewalks.