Urban heat opens door to negative public health effects

July 24, 2021. The high was 97 degrees outside, the hottest so far in July.

John Price walked into his home from work that day to see his wife Sarah nearly unconscious. Sarah, who has congenital heart disease, was suffering from a pre-heat stroke. Their AC unit had broken while he was gone, so the temperature inside was close to, if not over, 100 degrees. After calling an ambulance for her, he realized their dog Charlie was also showing signs of overheating.

“And he would always perk up, regardless of how he was feeling, whenever one of us would come in the door,” Price said. “That’s when I got close to his muzzle and saw that he was gone.”

Sarah’s health issues make it hard for her to handle high temperatures or move around unassisted for long periods of time. That day, the hot weather wore her out and made her dizzy — she felt too ill to make it down the steps of their mobile home with Charlie, leaving them both trapped.

Only a handful of miles away from their home in Platte City, the Kansas City International Airport recorded a temperature of 104 degrees. Exposure to excessive heat is notably dangerous, and in the case of the Prices, exposure had severe consequences.

Unfortunately, they are not alone.

Climate change touches every part of daily life, but for city-dwellers and suburban families alike, hot temperatures pose the unique threat of heat-related death or illness. What’s more, these higher temperatures can swell in the more urban areas of cities, causing them to have a higher temperature than their immediate surroundings.

Known as the urban heat island effect, or UHI effect, these pockets of above-average warm temperatures are caused by concrete in roads, sidewalks and buildings in a confined area and are contributing to noticeable increase in daily temperature compared to surrounding areas. With policies currently  in place to mitigate some of the potential concerns, there are possible structural solutions and policies with the potential to offer relief in the future.

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Ever since the Industrial Revolution in the late 19th century, the earth has been getting slowly warmer. According to NASA’s Earth Observatory, the average global temperature has gone up approximately 2 degrees Fahrenheit since 1880. A mix of natural variability and human activity is the cause, according to NASA and NOAA. What’s more, the 10 warmest years on record have all occurred since 2005, and seven of the 10 have occurred just since 2014, according to NOAA.

Temperatures in Kansas City and St. Louis usually differ about 4 or 5 degrees from rural areas, but the difference between these areas can be as high as 28 degrees in some cases, according to Fengpeng Sun, a climatologist and researcher at the University of Missouri — Kansas City. He said the reason behind the temperature differences is clear as day: in cities, there’s more man-made materials, such as concrete and asphalt, than natural ones like dirt and trees.

The main difference in temperature between urban and rural areas has to do with how well the surfaces in each environment absorb and hold heat, according to NASA. Darker objects, including most building materials, such as concrete and bricks, absorb more heat than they reflect.

This is, in part, a scientific principle known as thermal mass. Essentially, certain materials with a high thermal mass have a greater ability to absorb, retain and gradually release solar radiation.

“Because of urbanization, this area has been converted or been replaced with concrete or asphalt. So you’re going to significantly absorb the solar radiation,” Sun said. “And that’s the reason why, on the surface, the temperature is going to be warmer (in cities) compared to the surface where you have lots of vegetation.”

Have you ever wondered why stepping outside without shoes burns your feet on a hot summer day? This scorching surprise is immediately felt on surfaces made of concrete, and it’s easily explained by science.

Concrete is made with three primary ingredients: water, cement and what construction workers call aggregate — usually sand, gravel or a mix of both. When cement and water are mixed together, a chemical reaction called hydration occurs. Hydration is the process by which compounds within cement form chemical bonds with water molecules. After 28 days of curing this hydrated concrete, it’s fully equipped to absorb and hold in heat. This curing process is also known as an exothermic chemical reaction — it gives off heat.

An additional reason temperatures differ in urban and rural areas is due to “impervious surfaces” — primarily artificial materials like concrete that do not allow water to run through it. According to the EPA, replacing some concrete roads with more permeable materials would reduce heat island effects, with additional benefits in reducing runoff and pollutants.

But runoff and pollutants aren’t the only consequence of heat islands on the cities around them — public health is impacted by heat islands as well.

Dehydration and heat stroke are two of the most common symptoms experienced by residents in areas affected by the heat island effect, Sun said. In the case of John and Sarah Price, that’s almost exactly what happened. Other heat-related illnesses exacerbated by heat island effects include hyperthermia (a form of increased body heat and the counterpart of the more famous hypothermia), heat stroke and heat exhaustion, according to the EPA.

If any of the science talk seems confusing, think of it this way: cities can overheat in the same way humans do. And when these UHI areas reach dangerously high temperatures and stay there for extended periods of time, citizens face danger of overheating.

“If you know anything about fifth wheels and RVs in general, there’s usually not a lot of insulation to them,” Price said. “And with that massive heat wave that hit us last week and that seems to be coming back again, where it may have been 93 outside, it was over 100 in the trailer.”

Price was able to get his wife to a hospital in a timely manner, but heat exposure has deadly consequences for animals like Charlie and more vulnerable humans alike.

According to the Missouri Department of Health and Senior Services, there have been over 4,500 cases of hyperthermia in the state since 1980. Of those 4,500 cases, over 1,250 were fatal — the majority in the areas of Kansas City and St. Louis. It has a more severe impact on people who are over the age of 65 or under the age of 5.

Death by overheating is not just isolated in one part of the world or specific to one set of circumstances. A study from Nature magazine pointed to a worldwide increase in heat-related deaths, and came to the conclusion that almost 37% of heat deaths can be directly attributed to climate change sparked by human activity.

Heat islands can also intensify the impact of naturally occurring heat waves. Excessive heat events, or abrupt and significant temperature increases, are considered especially dangerous and can cause higher mortality rates. Between 2004 and 2018, 10,527 heat-related deaths were recorded in the United States, an average of over 700 per year. These numbers include deaths where heat was the underlying cause and deaths where heat was a contributing cause, according to the CDC.

Heat islands have had additional consequences outside the public health sphere — anything from higher operating costs to air pollution within the last three years.

First, increased energy usage is more prevalent. When heat islands occur, they lead to consumer’s increased demand for additional air conditioning. This leads to higher overall electricity expenses and increases in “peak” energy demand – which usually occur during hot summer afternoons, for example. In areas without robust utility systems, peak demand can exceed available electricity supplies and lead to controlled blackouts to avoid power outages. This was seen in Spokane, Washington and in other places across North America in the summer of 2021 because of the heat.

As mentioned earlier, heat islands play a role in increased demand for electricity — especially during the summertime. Today, many companies that supply electricity rely on power plants and fossil fuels to meet demand, according to the EPA. In turn, these plants can lead to an increase in air pollutants and greenhouse gas emissions such as carbon dioxide – a significant contributor to global climate change.

Not only the EPA, however, has found that  heat islands impact communities outside of public health, which is not a recent trend. Heat island effects and extreme heat have led to increased energy costs as early as in the last 10-12 years, according to the Federal Department of Housing and Urban Development.

Heat island effects correspond to an increase in demand for energy, according to a Climate Change Adaptation Plan released in June 2012. This increased demand usually takes shape in the form of more electricity to operate air conditioning units, which is almost exactly what the EPA found in the last 2-3 years.

Different programs under the HUD umbrella are particularly sensitive to what they call “extreme heat events,” especially programs that focus on low-income families and those with specific needs, such as the elderly, those with disabilities, people who are homeless or at risk of being homeless, among others. Some of the specific programs, such as Housing Choice Vouchers and Public Housing, have portfolios of living arrangements predominantly in urban areas. Because of the heat island effect, HUD noted, these urban areas tend to be more susceptible to extreme heat events.

HUD also noted that as demand for energy increases, so do operating costs for HUD’s housing portfolios. In 2010, HUD’s partners in different governmental and private sectors spent close to $7.1 billion in exclusively water and energy costs. Part of this can be explained due to two facts:

  1. Much of HUD’s public and assisted housing spaces were built before the introduction of “energy codes” to make buildings more energy-efficient. This has created challenges to addressing both affordability and environmental concerns for building residents, landlords and the federal government.
  2. Federal allowances for tenant-paid utilities in these assisted living units are mostly based on historical and regional costs. According to HUD, these allowances are not always sufficient to cover higher energy costs in energy-inefficient units, or spikes in energy costs due to extreme weather events such as heat.

While heat islands impact both public health and energy demands, it is not an issue without solutions.

This story was produced by the Missouri Information Corps, a project of the Missouri School of Journalism. Have tips for us? Email: moinformationcorps@gmail.com.


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