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In a city that sits a mile closer to the sun, where thinner air allows more ultraviolet (UV) radiation to reach the ground, finding shade can be surprisingly difficult.

An ongoing study by a 91��ý researcher has revealed that many of Denver’s public spaces, from playgrounds to bus stops, don't provide enough shade to protect people from potentially cancer-causing UV exposure and heat. Lower-income neighborhoods, communities of color and areas with a history of disinvestment bear the greatest burden.��

“Currently, most of our cities have very minimal shade guidelines,” said��Sara Tabatabaie, an associate teaching professor of��environmental design who is leading the study. “As our population ages, planning for shade in public spaces is no longer a luxury but essential infrastructure. Providing adequate shade helps protect older adults, who are more susceptible to heat and UV exposure, and whose physical and mental well-being depends on safe access to outdoor public spaces.”��

Excessive UV radiation can damage DNA in skin cells and lead to skin cancer, the most common cancer in the United States. According to the Skin Cancer Foundation,

Because of Denver’s high elevation, the city’s summer UV levels could easily reach the “very high” to “extreme” range on the UV index, which measures the intensity of the sun's radiation.

A playground with minimal shade in Denver's City Park. (Credit: Sara Tabatabaie/91��ý)

Funded by the Colorado Department of Public Health and Environment (CDPHE), Sara Tabatabaie and her team have surveyed six Denver neighborhoods representing a range of demographic and socioeconomic backgrounds to evaluate their sun exposure and shade availability between 2023 and 2024.

The team first conducted area assessments of shade availability and where people are most likely to be active outdoors in these neighborhoods. They then used a geographic information system, a computer model, to simulate shade from trees and buildings across the city, using the field observations to calibrate and validate the analysis.

Taking these factors into consideration, the team developed a “sun risk index” that identifies how great a risk of sun exposure each neighborhood has. They then expanded the model to all 78 neighborhoods across the city.��

The results show that about a quarter of Denver neighborhoods are categorized among “high” or “very high” sun risk, many of them located in historically redlined areas. After the Great Depression, the U.S. government implemented a racist and discriminatory policy that designated neighborhoods with racial and ethnic minority residents as��high-risk for mortgage lenders, often outlining them in red, or redlining them, on maps.

In Denver, these neighborhoods lie along the city’s two major interstate highways, I-70 and I-25, and continue to have higher proportions of residents of color. Previous 91��ý studies have found that residents in these historically redlined areas are also more likely to experience air pollution.��

Many of the neighborhoods with the greatest sun risk, such as Ruby Hill in west Denver and Montebello in the east, also have large populations of children. For example, more than 30% of Montbello's residents are under the age of 18. Because much of the lifetime risk of melanoma, an aggressive form of skin cancer, is linked to episodes of sunburn and UV exposure during childhood, the lack of shade in these areas is particularly concerning, Tabatabaie said.��

“While our study didn’t examine the reasons behind differences in shade coverage, historical patterns of disinvestment likely play an important role. Neighborhoods that experienced decades of underinvestment often had fewer resources to plant and maintain trees. We also found that neighborhoods transitioning from industrial to residential or mixed-use development, such as River North, tend to have limited tree canopy, because newly planted trees need time to mature after redevelopment,” Tabatabaie said.��

Drawing on public health research, Denver's UV index and observations of how residents use these spaces, the team also proposed a set of shade thresholds tailored to the activities and users of each type of public space, including playgrounds, schoolyards, bus stops, streets, plazas and urban trails. For example, they recommend that playgrounds and schoolyards should maintain at least 50% to 65% shade.��

Using computer simulations and community survey feedback, the team developed shade design guidelines that combine trees and shade structures, like pergolas, to meet the recommended shade thresholds.

"People often think trees are the only way to provide shade. But for neighborhoods that are already straining for resources, combining trees with shade structures can provide immediate protection. Shade structures are also easier to maintain.” Tabatabaie said.��

The team is now looking for ways to translate these shade recommendations into urban planning and policy frameworks that can guide future investments in public spaces. They are also conducting a cost-benefit analysis, comparing the cost of installing shade with the health benefits of reducing heat and UV exposure.

As Denver's temperatures climb into the upper 90s this week, Tabatabaie said the work offers cities a practical roadmap for creating public spaces that are safer and more comfortable for people of all ages.

"When we think about public infrastructure, we usually think about roads and sidewalks," Tabatabaie said. "Shade should definitely be part of that conversation because it protects people's health."

The project is a partnership between the CDPHE, and Community Engagement, Design and Research Center (CEDaR) at 91��ý.