No respite
As Dr. Ebi says, the key to preventing heat-related death is to cool down enough to stabilize our internal cells and proteins before the irreversible cascade begins.
But for close to 80% of Americans who live in urban areas, temperatures can be even higher and more intolerable compared to surrounding areas because of the way we’ve designed our cities. In effect, we have unintentionally created hot zones called “urban heat islands.”
Jeremy Hoffman, PhD, chief scientist for the Science Museum of Virginia, explains that things like bricks, asphalt, and parking lots absorb more of the sun’s energy throughout the day and then emit that back into the air as heat throughout the afternoon and into the evening. This raises the air and surface temperatures in cities, relative to rural areas. When temperatures don’t cool enough at night, there’s no way to recover from the day’s heat. You start the next day still depleted, with less reserve to face the heat of a new day.
When you dig even deeper, it turns out that even within the same city, there are huge “thermal inequities,” as Dr. Hoffman calls them. In a 2019 study, he found that wealthier parts of cities had more natural spaces such as parks and tree-lined streets, compared to areas that had been intentionally “redlined,” or systematically deprived of investment. This pattern repeats itself in over 100 urban areas across the country and translates to huge temperature differences on the order of 10-20 degrees Fahrenheit within the same city, at the exact same time during a heat wave.
“In some ways, the way that we’ve decided to plan and build our cities physically turns up the thermostat by several tens of degrees during heat waves in particular neighborhoods,” Dr. Hoffman said.
Dr. Hoffman’s work showed that the city of Portland (where the death toll from the heat wave in late June was the highest) had some of the most intense differences between formerly redlined vs. tree-lined areas out of the more than 100 cities that he studied.
“Watching it play out, I was really concerned, not only as a climate scientist, but as a human. Understanding the urban heat island effect and the extreme nature of the inequity in our cities, thermally and otherwise, once you start to really recognize it, you can’t forget it.”
The most vulnerable
When it comes to identifying and protecting the people most vulnerable to heat stress and heat-related death, there is an ever-growing list of those most at risk. Unfortunately, very few recognize when they themselves are at risk, often until it’s too late.
According to Linda McCauley, PhD, dean of the Emory University School of Nursing in Atlanta, “the scope of who is vulnerable is quickly increasing.”
For example, we’re used to recognizing that pregnant women and young children are at risk. Public health campaigns have long advised us not to leave young children and pets in hot cars. We know that adolescents who play sports during hot summer months are at high risk for heat-related events and even death.
In Georgia, a 15-year-old boy collapsed and died after his first day back at football practice when the heat index was 105° F on July 26, even as it appears that all protocols for heat safety were being followed.
We recognize that outdoor workers face devastating consequences from prolonged exertion in the heat and must have safer working conditions.
The elderly and those with long-term medical and mental health conditions are also more vulnerable to heat. The elderly may not have the same warning signs and may not recognize that they are dehydrated until it is too late. In addition, their sweating mechanism weakens, and they may be taking medicines that interfere with their ability to regulate their temperature.
Poverty and inadequate housing are risk factors, especially for those in urban heat islands. For many people, their housing does not have enough cooling to protect them, and they can’t safely get themselves to cooling shelters.
These patterns for the most vulnerable fit for the majority of deaths in Oregon during the late June heat wave. Most victims were older, lived alone, and didn’t have air conditioning. But with climate change, the predictions are that temperatures will go higher and heat waves will last longer.
“There’s probably very few people today that are ‘immune’ to the effects of heat-related stress with climate change. All of us can be put in situations where we are susceptible,” Dr. McCauley said.
Dr. Moseson agreed. Many of her patients fit none of these risk categories – she treated people with no health problems in their 20s in her ICU, and the patient she lost would not traditionally have been thought of as high risk. That 50-something patient had no long-standing medical problems, and lived with family in a newly renovated suburban home that had air conditioning. The only problem was that the air conditioner had broken and there had been no rush to fix it based on past experience with Oregon summers.