Urban Heat and Health (Extended Coverage)

Richard Keller, PhD, Professor, University of Wisconsin; Author, Fatal Isolation

I want to talk today about that 2003 European heat wave, with a particular focus on Paris. It pushed temperatures well above 100° F throughout much of Europe for about two weeks, and evening lows really only dropped to the mid-70s, which left little respite. This came after two earlier and nearly equally intense heat waves, which had already left many vulnerable Europeans on their knees. The consensus is that high summer heat entailed the excess deaths of some 70,000 Europeans that summer, and the August heat wave alone in France killed nearly 15,000 people. About 1,000 of them were in Paris, and that makes this the worst national disaster in French history.

To give some perspective, in a normal period, Paris’s morgue services shuttle about 40 bodies throughout the city in a given day, and in just three days in August of 2003, they transported nearly 800. The disaster also struck unevenly. About 80% of the mortality-burdened were those over 75 years old. Those in cities also paid a significantly higher toll. Paris has about 3% of the country’s population, but it suffered about 7% total mortality during the disaster, a disproportionate burden by any measure.

Social inequalities and vulnerabilities were laid bare by the disaster, and I especially want to address some of the ways in which architecture and urban planning might have had something to do with this kind of uneven distribution. There are all kinds of legitimate physiological and meteorological reasons why the elderly in cities, in particular, might have higher mortality than other populations. As we age, our bodies get less efficient at thermal regulation and sensing dehydration.

So we’re more vulnerable in that respect. Likewise, the urban heat-island effect plays a critical role, and some of the epidemiology suggests this was at play. A map of excess mortality by neighborhood in Paris shows the 13th and 15th arrondissements, which are basically textbook examples of urban heat islands: there’s virtually no green space; lots of concrete, lots of waste heat. If you look at some adjacent neighborhoods right next to these complexes, you can see more traditional 19th-century Haussmannian architecture, which actually suffered significantly lower mortality.

Without dismissing the critical effect that heat islands might play, there’s more we need to dig into, a huge social component to address. There’s plenty of mortality to go around in neighborhoods marked by the classic Haussmannian architecture that characterizes most of Paris, and indeed you can argue that increased mortality in these sites is actually in many ways a function of the building style itself. If we look at the 19th-century remaking of the city, in a cross-section of a typical Haussmannian building, we can see the development of a new geography of inequality that operates on a vertical plane. As you ascend the staircase in one of these buildings, you’re actually descending the socioeconomic ladder, so when you get to the top, right up under these zinc and aluminum roofs, the heat loads become higher, the spaces are smaller, ventilation is less effective, people become poorer, and they also become more socially isolated. In particular, the elderly poor suffer from these kinds of conditions with seven-story spiral staircases effectively imprisoning many of those older than 75 with increased disabilities. These spaces also have fewer amenities, with some not even having running water or toilets on the same floor, let alone baths or showers. It’s no wonder that the risk of dying in these kinds of conditions is about 133% higher than those who lived even a single floor below. There’s a vertical geography of vulnerability that we need to think about as we think about heat islands.

The second point is, even in neighborhoods that constitute true heat islands, there are important social factors at work that influence urban sociability. The Olympiades complex was built on the site of a former slum that the city razed in the 1960s, and the replacement of these former buildings displaced the community, who could no longer afford the higher rents imposed by the new construction. Another phenomenon attended the re-composition of the neighborhood: the shuttering of many local businesses. The number of cafés and bakeries declined by 90%. In the Rue Nationale alone, there were 48 of these cafés that were actually replaced by just one. More than merely coffee shops, these cafés offered a living space for people who suffered daily indignities of living in tiny, overcrowded, and unhealthy apartments. While the redevelopment of the neighborhood may have dramatically cleaned up the area, it also fragmented the existing community.

These new conglomerations also engender insularity. With many essential services located right on the campuses, people tend not to leave. This reinforces social isolation, and any adventure into the outside world entails a long wait for an elevator, followed by an often circuitous route down to the sidewalk. Closing these centers of social life assumes a new importance if we think about these neighborhoods’ staggering mortality. If you consider that social isolation is a critical factor that exacerbated mortality risk during the heat wave, we need to think about how isolation is becoming a way of life for many of the elderly.

I want to close with an anecdote: a café in the 16th arrondissement was a social hub in the neighborhood where I lived when I was conducting my fieldwork. This happens to be in the neighborhood of the lowest mortality during the heat wave. So I stopped here for coffee every morning before I set out to do my research, and there was also an old man who came into the café every morning with his dog. Every morning he would hand a little vial to the bartender and then lean backward over the bar, and the bartender would give him his eye drops — his glaucoma medicine. I think this is more than a medical action; I think it’s actually a symptom of a kind of social coherence that marks this neighborhood and that might attest, to some extent, to its low mortality rate. It suggests that we need to consider not just heat islands but social worlds if we want to understand vulnerability and resilience in a period of rapid climate change. In other words, I think Jane Jacobs was right.


Tom Matte, Assistant Commissioner for Environmental Surveillance and Policy, NYC Department of Health and Mental Hygiene

Urban densification has tremendous potential benefits for the larger environment, public health, and sustainability. But it also exposes urban residents to certain hazards disproportionately: not just extreme heat but also air pollution, noise, being stranded in high-rise buildings. How do we continue to leverage the benefits of that compact, sustainable urban form while protecting and promoting public health, especially among the most vulnerable and marginalized populations?

Heat illness and death fall into two broad categories: there’s heat-specific illness, hypothermia, which can be counted. The people’s names can be known. And then there’s an increase in serious illnesses and death from chronic health problems like heart disease, lung disease, and so forth. Those excess deaths and illnesses are actually much larger in number than the heat-specific deaths. When the heat index (temperature and humidity combined) makes it feel like it’s about 95° or above, risks start to rise in a nonlinear way: there are on average between 10 and 15 hyperthermia deaths, more like 100 excess natural-causes deaths, during extreme heat events. Excess mortality and morbidity also occur in the seasonal hot weather that we have in New York City, and that has implications for prevention and the built-environment changes we need to make.

The potential for a more catastrophic heat wave is always there. If you apply the mortality rate from the northern European and French heat wave to New York City, that would be something like 2,000 deaths from a single natural disaster. What might cause something like that to happen in New York? It could be the combination of an extended heat wave and widespread power outages; during the 2003 citywide outage that lasted just about 36 hours, there were close to 100 excess natural-cause deaths, and excess morbidity and mortality from that event were not limited to low-income neighborhoods. There’s some evidence that it was actually neighborhoods with lots of high-rise buildings; even more affluent neighborhoods, had more of an increase in respiratory illness during the 2003 blackout.

Our role in the Health Department is to use data on health impacts and vulnerability to inform how the city prepares for and responds to heat waves. Most of the people who die from heat stroke are exposed at home, don’t have working air conditioning, or weren’t using it at the time of death. People with chronic physical and mental health conditions are almost always present among these hypothermia deaths. At the neighborhood level, we see a combination of measures of social disadvantage (poverty concentration, African-American race) as well as physical-environment differences (higher surface temperatures, less green infrastructure, less vegetative cover). We estimate about 25% of New Yorkers either don’t have or don’t use air conditioning at home during extreme heat; half stay home even when it’s too hot. If we look at the overlap of that population and people who have a health risk, that’s about a half million New Yorkers. We’ve been trying to improve the kinds of messages that go out at the beginning of heat season and the audiences that they get to, so that people know what they need to protect themselves, clients, neighbors, family, and friends. We would really benefit from better models of the urban heat island and how it affects interior temperatures and people on the stret, so that we could communicate to city leaders who have to make investments.

Whenever I talk at any sort of climate health meeting, there’s always the question, “Why are you promoting air conditioning as a protective measure?” In New York City we’re using an enormous amount of air conditioning. Energy used to cool spaces more than they need is not only straining the electric grid, it’s producing more air pollution, because it’s using the peaking units that are needed to maintain power on the hottest days of the year, and it’s producing waste heat. Learning how we can change that behavior could be low-hanging fruit. Certain people need air conditioning; we need to figure out creative ways to get them access to it, either in their unit or in cooling centers or lobbies. But then other people need to be using air conditioning responsibly and need an awareness of how there’s an externality to using it in a commercial or residential space.


Melissa Umberger, Hazard Mitigation Project Manager, NYC Department of Emergency Management

When there is an emergency, we are the lead coordinating agency for making sure all the right people are in the room to collect and disseminate critical information to our city partners and the public. We also have extensive campaigns for preparing the public for all types of emergencies. Due to the complexity of cross-cutting hazard impacts, our agency takes two approaches to planning: all-hazards plans and hazard-specific plans. We have a Heat plan for extreme heat events and at the same time a Power Disruption plan applicable to many different hazards; for an extreme event typically we activate both protocols simultaneously. Our activation criteria are a projected increase of a heat index of 100° F or more for any period of time and a heat index of 95° F for two consecutive days or more. In 2014 we modified some of our protocols because of climate change and the frequency and intensity of heat waves.

Our Advanced Warning System has a two-pronged approach: conference calls and blast e-mails to our partner agencies, service providers, and umbrella organizations that serve the needs of populations that have disabilities or other access and functional needs. We’re providing targeted information, usually including a forecast from the National Weather Service, heat tips, preparedness measures that individuals can do, and the location of our cooling centers. Our “Beat the Heat” guide, available in 91 different languages, provides preparedness tools, things like promoting the use of air conditioning and checking in on your friends and family, especially those that might be vulnerable. Cooling centers are air-conditioned facilities, open and free to the public; they typically already serve the community as a library, senior center, or community center. We leverage our partner agencies: the Department for the Aging, the New York City Housing Authority (NYCHA), and the Department of Youth and Community Development, who will use their facilities for a dual purpose. We also increase our homeless outreach; the Department of Homeless Services has a Code Red, sending out monitoring teams on the street. Our Watch Command Office receives information 24/7 from Con Edison and other entities, will get information about power outages and voltage reductions; during extreme heat events we may send a liaison from our agency over to Con Edison to monitor that system and coordinate resource requests.


Sabrina McCormick, PhD, Associate Professor of Environmental and Occupational Health, George Washington University; Filmmaker

I’m speaking to what I have seen so far is a minority of people interested in this subject. As a qualitative sociologist who spends a lot of time going to cities across the country, I can tell you that you are ahead of the curve. One research project is a focused deep dive on heat and vulnerable populations in New York, Philadelphia, Detroit, and Phoenix in a collaboration with folks at the University of Michigan and Harvard; there’s a more recent project on climate adaptation in Tampa, Raleigh, Portland (Ore.), Los Angeles, Boston, and Tucson. We’re looking at how city officials, NGOs that work with them, and governments more generally perceive and address heat risk, and how vulnerable populations perceive their own risk and respond to it. There’s been limited concern about heat, but since I’ve been working on this for almost a decade, this has shifted, and we see some cities becoming more and more concerned. Having said that, their actions to address heat risk have been limited: there’s a decent amount of planning in some places, but less implementations of heat-adaptation programs.

Vulnerable populations, especially people over 65 living in dense, hotter areas, where I”ve done the most interviewing, tend to not recognize heat as a risk factor. When they do, they engage in self-protective reactions: they drink water, stay inside, take a cold shower, use a fan; they sometimes go to a cooling center, a park, or shopping; and sometimes they use their AC. Residents have expressed concerns about paying for the electricity, or risks to the air conditioner and potential fire in old buildings, when it’s on a long time. There are preconceptions and stigmatizations of cooling centers in some places; vulnerable populations can think a center is occupied by – and this is their language – “drug addicts, people on parole, and alcoholics.” There are places where people feel uncomfortable going for a number of reasons. There are also transportation barriers. It’s very important that we emphasize, as I think this community probably does, developing cooling resources that are not just access to cooling centers or access to air conditioning, because we face major obstacles in actually convincing people that they’re at risk and that they can use their AC.

In basically every city where I’ve done research I see disjuncture between public-health officials and urban planners. There is a constant need to inform the public and all those whom we work with about the risk of heat waves; it’s a risk that I find people chronically underestimate. I’m also a filmmaker, and I was a producer on a story in The Years of Living Dangerously, a Showtime series about climate change. I produced the story with Matt Damon as a correspondent investigating heat risk in Los Angeles. We introduce him to a woman who has gone into preterm delivery during a heat wave; she has no idea that heat is a risk factor. She is rushed to the emergency room and put on two bags of saline, and they prevent this preterm birth (increased rates of preterm delivery during heat waves is an increasing concern, especially in urban areas). She tells Matt this story, and his face gets shocked and blank; he says “You know what? That exact same thing happened to my wife.” People who are the most vulnerable and people who in some ways are the least vulnerable really know very little about heat. We need to be continually educating both city-level decision makers and vulnerable populations around the world.


Elan Levy, MD, Attending Physician, Emergency Department, Lenox Hill Hospital/Lenox Health Greenwich Village, North Shore-LIJ Health System

Our body temperature is maintained by balancing heat load with heat dissipation. We have a remarkable resilience against cold but can only tolerate minor fluctuation with temperature increase without developing systemic dysfunction. As our core temperature rises, the hypothalamus stimulates the nervous system to cause changes in the skin and the way we sweat. Evaporation, when water vaporizes from our skin and our respiratory tract, is the body’s most effective mechanism for dissipating heat. During exercise our body needs an intact cardiovascular system, which uses blood to transfer heat from our core to the skin, where these mechanisms for heat dissipation can take effect. When ambient temperature is higher than our core temperature, or when humidity exceeds 75%, these means of heat dissipation are no longer effective. Temperature elevations also cause a rise in oxygen consumption as well as the metabolic rate and also cause certain enzymes to cease to function. The cells in the brain, liver, and peripheral vascular system are susceptible to increased heat.

The most important heat-related illness is heat stroke, a multisystem, life-threatening illess that  occurs in the setting of extreme heat that cannot be dissipated. It’s characterized by central-nervous-system dysfunction, which manifests with disorientation, headache, and irrational behavior and can even precipitate to seizures and coma. There has to be a core temperature above 104° F and exposure to severe environmental heat. There’s also a high mortality risk associated with heat stroke: anywhere from 21% to 63%. The two types are exertional and nonexertional (or classic) heat stroke. Exertional heat stroke is typically in an unacclimatized young person exposed to a heat stress over just a few hours; clinically they’re still able to produce sweat, as opposed to classical heat stroke, where it’s either the very young or very old, it’s a gradual onset over several days, and they present severely dehydrated, typically with dry, hot skin. Minor heat-related illnesses include heat exhaustion and heat syncope, which may mimic heat stroke or be precursors for it but lack that elevation in core temperature, along with heat cramps, tetany, or rash.

Acclimatization is the body’s ability to improve its response in tolerance to heat stress over time and is much more important with exertional heat illness. It typically requires one to two weeks but can take as long as 60 days; some of the physiologic changes include increase in blood volume, improved blood flow to the skin, a lower threshold of the initiating of sweating, and a lower concentration of salt and sweat.

Criteria that put someone at risk for classical heat stroke are age older than 70 and chronic medical conditions such as cardiovascular disease, respiratory disease, physical debilities, mental illness, and obesity. Risk groups also include those with a lack of access to air conditioning, the socially isolated, those who are unable to care for themselves, users of recreational or prescription drugs, and children. Children have a higher basal metabolic rate, which causes increased heat production; a higher surface-area-to-mass ratio, which causes greater heat absorption from the environment; and a smaller absolute circulating blood volume, which limits the transfer of blood from the core to the periphery, the main mechanism of heat dissipation. They also sweat at a lower rate, they don’t adequately replenish fluid losses, and the acclimatization process occurs at a much lower rate than an adult’s.

Many medications and substances can put someone at risk for heat stroke: alcohol, anticholinergics, seizure medications, psychiatric medications, decongestants, diuretics, antihypertensives, stimulants, and antihistamines. These are used to treat a variety of illnesses, including cardiovascular, neurologic, and psychiatric diseases; they’re often taken together in combination. Generally speaking, they can cause dehydration, confusion, kidney injury, and impaired thermoregulation. In the emergency department, one would see an elder patient typically with numerous medical conditions and a myriad of medications, usually living alone and found unresponsive by a family member, caretaker, primary medical responder, or even superintendent. It’s typically on a hot or humid day in a place that lacks a functional air-conditioning unit.

The clinical presentation is that they’re confused, they have a fever, their skin is hot and dry, and they have a low blood pressure and high heart rate. This can mimic other presentations we see in the emergency department, so it’s important for us to be cautious and thorough when evaluating them. The mainstay of emergency treatment is the ABCs: airway protection, monitoring the breathing, and circulation. Evaporative cooling is the most successful method of treating classical heat stroke: disrobing the patient, spraying with lukewarm water, and using a fan to blow water over the moist skin (cold-water immersion is less effective due to the monitoring devices on these patients). Ancillary icepacks are useful, as well as cool intravenous fluids and saline; temperature monitoring is of the utmost importance, with a goal of less than 101°F. Workup consists of blood counts, urine testing, and imaging. The mortality rate ranges from 21% to 63%, correlating with the degree of temperature elevation, time to initiation of cooling, and number of organs affected. Complications include but are not limited to respiratory failure, arrhythmias and cardiovascular collapse, and kidney and liver dysfunction.

Prevention of heat stroke should be a public-health concern and a multidisciplinary approach. As general recommendations for patients and their caretakers: rest, drink cool nonalcoholic beverages, wear lightweight clothing, remain indoors during the hottest times of the day, limit strenuous activity, facilitate transport to air-conditioned locations, and watch for signs of heat exhaustion. If these are present in someone that you know, please expedite removal of the person from that environment and contact with emergency medical services.

Our own institution is New York City’s first freestanding emergency department, with a volume of 30,000 visits last year; during times of disaster, we would quickly discharge anyone in the ED through safe measures and prepare for a massive influx of new patients. In a massive heat wave, those with minor illnesses would be cared for in our department, and those needing an immediate higher level of care or stabilization would be placed in our resuscitation room and tagged with the  New York State Evacuation of Facilities in Disaster System (EFINDS) for location and tracking throughout the health commerce system. The take-home points here are to understand the differences between exertional and nonexertional heat stroke, recognize at-risk populations and risk factors, and understand some preventative measures for high-risk populations.