# Presentation: 657300

## Health Effects of Exposure to Extreme Heat

**George Luber, PhD**
**Division of Environmental Hazards and Health Effects**
**National Center for Environmental Health**
**Centers for Disease Control and Prevention**

**Notes:**
Good afternoon, 

I would like to begin by extending my thanks to the conference committee for orgainizing this session and giving 

for this opportunity to talk on an important emerging public health threat:  heat waves.   

## Presentation outline

- An overview of the epidemiology of heat waves
- The impact of climate change on extreme heat exposure
- Current CDC activities

**Notes:**

Today’s talk will summarize some of the health impacts of exposure to extreme heat and highlight some of the activities CDC has undertaken to mitigate some of the effects 

I’ll begin this presentation will an overview of the heat related illnesses and discuss the current state of knowledge about the epidemiology of heat waves, 

This will be followed by a discussion of the potential impacts of climate change on extreme heat exposure and 

Finally, I will conclude with an overview of some current CDC activities in this area.

## Heat Waves

**High mortality**
- More deaths than hurricanes, 			     lightning, tornadoes, floods, and 	             earthquakes combined.
- From 1999–2003, total of 3,442 _reported_ heat-related deaths.  Annual mean of 688 (MMWR 2006)
**Lack of public recognition**
- No damage to infrastructure (silent killer)
- Many deaths go unreported or unattributed
**Every death is preventable**

**Notes:**
Heat waves are not new phenomena; they have been quietly killing the most vulnerable residents of our cities for centuries 

In the United States, exposure to extreme heat is responsible for more deaths annually than hurricanes, lightning, tornadoes, floods and earthquakes combined. Over a 5 year period, from 1999–2003, there were a total of 3,442 reported heat-related deaths, for an annual average of 688. 

But, despite the lethality of heat and heat waves, there is still a lack of public recognition of the hazard of extreme heat exposure.
Part of the problem lies in the fact that heat waves are silent killers--natural disasters that don’t leave a trail of destruction in their wake.  Like other natural disasters they are sporatic phenomena, but unlike hurricanes, which leave lasting reminders of the devastation, memories of the heat wave disappears once cool weather arrives. 

From a public health viewpoint, another major obstacle lies in the fact that the true impact of heat waves is largely underestimated because many heat-related deaths are unreported or unrecognized as heat-related.  Bodies found days after a heat wave, with no core temperature to record, often are not coded on death certificates as heat-related.  Furthermore, increases in hospital visits and deaths due to cardiovascular and respiratory diseases have been documented during heat waves, suggesting that heat exacerbates these conditions as well.  The inability, or failure to attribute these increases in mortality to the heat wave event has been a persistent challenge.  

At some fundamental level, each heat-related death represents a failure of the public health and social welfare system But despite these obstacles, it is our position that each and every heat-related death is preventable.

## Heat Wave Studies

- 1980		St. Louis
- 1st to highlight the magnitude of  				mortality from heat waves
- All cause mortality increased  57%
- 1993		Philadelphia
- Identified cardiovascular mortality as a major cause of death associated with extreme heat
- 1995		Chicago
- Redefined heat-related death as used by medical examiners
- Assisted with the development of a Heat Wave Response Plan

## MMWR 1995

**MMWR 1995**

**2 day lag**

**Notes:**
Another important finding to emerge from the 1995 Chicago heat wave investigation was the relation between peak temperature, heat index, and mortality.  

This graph shows maximum temperature, heat index, and the number of heat-related deaths during the 1995 heat wave in Chicago

Note the two day lag between max temp and deaths.  

This finding has important implications for it suggests that medical examiner surveillance should not be used as triggers for the activation of a public health response, including the provisioning of emergency cooling centers, instead a response must be activated when a heat-wave is forecast, not after illness or deaths are reported.  

## Heat Wave Studies

- 2003 France
- 34,000+ dead in Europe
- 14,000+ dead in France
- Many were elderly in nursing homes
- No effective method to cool

**Notes:**
Perhaps the most startling reminder of the potential lethality of heat waves was the August 2003 European Heat Wave, which was responsible for over 34,000 deaths across Europe and more than 14,000 deaths in France alone. 

A combination of several factors were responsible for the high death rate, including a general lack of appreciation of the lethality of heat waves as evidenced by the fact that many health care professionals, who were on annual summer holiday in August, were not recalled to duty by the Ministry of Health.   

Tragically, many of the victims of this heat wave in France were the elderly under supervised care in nursing homes, most of which were not equipped with air-conditioning or other means of cooling.  Even cold baths, an inconvenient but effective option, were not able to be used for cooling because of the high ratio of residents to showers.  It would have taken days to give all the residents a single turn, ruling out this option.  

## Lessons Learned 

- _Risk factors for hyperthermia:_
- Age
- Underlying medical conditions / mental illness
- Income and poverty status
- Homelessness
- Social isolation
- Access to health care and cooling facilities
- Neighborhood characteristics: land use/ land cover, crime rate, housing type, urban heat island

**Notes:**
These investigations, along with others have highlighted some of the most important risk factors for hyperthermia and heat-related death, including

--age:  the elderly and very young are most vulnerable because they are not able to thermoregulate efficiently because of their higher sweating thresholds,thus increasing the risk of life-threatening consequences when their body temperatures rise 

--those with underlying medical conditions such as cardiovascular and respiratory disease, obesity, and even mental illness are at increased risk

--poverty represents the combined risk of reduced health status and access to protective measures such as air conditioning: 

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Increased risk is not limited to individual factors but also include features of the built environment that accentuate the health risks of heat waves including access to transportation, medical care and cooling centers as well as crime (necessitating keeping windows and doors closed for safety reasons), housing type and the urban heat island effect.  

## Temperature-mortality relation for 11 US cities, 1973–1994 

**Notes:**
Another important epidemiologic insight gained from long term analysis of temperature and mortality is that cities have a temperature at which mortality is lowest. Mortality rates rise at temperatures outside this comfort zone 

This figure shws thel U-shaped relation between temperature and mortality for 11 US cities. The trough represents the comfort zone; the steeper (right-side) arm of each line shows the mortality increase at hot temperatures, and the shallower (left-side) arm of each line shows the increase with colder temperatures. 

What’s most important about this analysis is that the temperature-mortality relation varies greatly by latitude and climatic zone. In general, northern cities are more vulnerable to high temperatures and southern cities to low temperatures. 

Understanding the city-specific relation between temperature and mortality is critical for developing an appropriate public health respnse

## Climate Change Predictions 

**Intergovernmental Panel on Climate Change (IPCC): **
*	**	*
*	**	**	**“**Cities that currently experience heat waves are **	**	**	**expected to be further challenged by an **	**	**	**	**increased number, intensity and duration of **	**	**	**heat waves during the course of the century.”* 			[very high confidence]

**Notes:**
While urban areas of the United States are currently challenged by the high morbidity and mortality of heat waves a larger challenge is looming.  

The Intergovernmental Panel on Climate Change, the leading international scientific body on the effects of climate change predicts an increase in the duration, intensity and frequency of heat waves in the coming century.  

The fact that the IPCC, a body known for their highly conservative predictions of the impact of climate change, estimates this outcome with a very high confidence, underscores the certainty that this will become a major public health problem this century.

## A July day in Atlanta that now reaches a heat index of 105°F would reach a heat index of 115°F in the Hadley model, and 130°F in the Canadian model. 

- July Heat Index Change -- 21st Century

- Map by B. Felzer, UCAR, based on data from Canadian and Hadley modeling centers.

**Notes:**
An indication of the magnitude of the impact climate change will have on temperatures is illustrated here. 

These maps show the projected increase in average daily July heat index (a measure which combines heat and humidity) for the coming century, relative to the present. The largest increases in temperature are found in the southeastern states, where the Canadian model projects increases of more than 25°F. 

For example, a July day in Atlanta that now reaches a heat index of 105°F would reach a heat index of 115°F in the Hadley model, and 130°F in the Canadian model. 

## Urban “built” environments

- Cities and climate are coevolving in a manner that will place more populations at risk.
- Increase in vulnerable populations:
- Today, more than half of the world’s population lives in cities, up from 30% in 1950.
- By 2100 there will be 100 million more people > 65 years old (relative to 2000) (Ebi et al. 2006).
- Urban heat islands

**Notes:**
Adding to the climate change-driven increases in temperature are the added effects of the urban “built” environment

In fact, cities and climate are co-evolving in a manner that will certainly amplify both the effect of heat as well as the vulnerability of urban populations to heat-related death, for example:

More than half the planet now lives in cities, up from 30 percent only 50 years ago. Urban areas are gaining an estimated 67 million people per year—about 1.3 million every week. By 2030, approximately 60% of the projected global population of 8.3 billion will live in cities. 

Additionally, there is a projected increase of 100 million more persons greater than 65 years of age by the year 2100   

This population increase will be accompanied with rapid urbanization which is quickly transitioning communities from native vegetation to an engineered infrastructure that increases thermal-storage capacity, resulting in significant change in the urban climate compared to adjacent rural regions, known as the Urban Heat Island Effect (UHI)

## Urban Heat Island can add 7° – 12° F

- Thermal Satellite Image of Phoenix, AZ Night Surface Temperature

**Notes:**
The urban heat island can be a powerful force in local climate, as illustrated by the urban heat island diagram on the upper right.  The combined effect of the high thermal mass provided by concrete and blacktop roads, and the low ventilation ability of the urban “canyons” created by tall buildings serve to extend the temperature increases created by climate change.  

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In real terms, relative to the surrounding rural areas, urban heat islands can add from 7 – 12 degrees Fahrenheit to the urban heat load.   

More importantly, the urban heat island serves to absorb heat during the daytime and radiate it out at night, raising the nighttime minimum temperatures, which have been epidemiologically linked with excess mortality. 

This satellite thermal image of nighttime surface temperature in Phoenix vividly illustrates this effect.   

- Slide on the Phoenix neighborhood study

- Neighborhood Microclimates within the UHI

- Harlan et al 2006

**Notes:**
In another study looking at the degree to which climate can vary within the urban heat island, Harlan and colleagues at Arizona State University compared 8 neighborhoods within Phoenix to look for differences in exposure to heat stress.  

They quantified and compared neighborhood ecological characteristics such as land cover, vegetation type, settlement density as well as sociodemographic characteristics such as age, income, education, and availability of resources to cope with heat such as air conditioning and swimming pools.  They found statistically significant differences in temperatures between the study neighborhoods during the entire summer, which increased during a heat wave period.  High settlement density typified by apartment buildings, sparse vegetation, and having no open green space in the neighborhood were significantly correlated with higher temperatures and thermal comfort index. 

Lower socioeconomic and ethnic minority groups, represented here by the Black Canyon Freeway neighborhood, were more likely to live in warmer neighborhoods with not only greater exposure to heat stress but in an environment that lacked resources to cope with it.  In comparison, the upscale Historic Anglo Phoenix neighborhood, which has lush landscaped properties, ample greenspaces, and a high-percentage of houses with air-conditioning and pools experience significantly less heat exposure.

If we compare average summertime mean maximum temperature for the two groups, we notice that the historic anglo neighborhood is about 7 degrees cooler on average.  But these differences are amplified during the critical times such as heat waves where the difference jumps to 14 degrees Fahrenheit.  In sum, people in warmer neighborhoods were more vulnerable to heat exposure because they had not only greater exposure to heat but also had fewer social and material resources to cope with it.

## CDC activities

- Guidance on the development of         city-specific heat response plans
- Vulnerability mapping using remote sensing

**Notes:**
To respond to the multiple threats posed by heat waves, the urban environment, and climate change, CDC has have focused prevention efforts on developing tools that local emergency planners and decision-makers can use to prepare for and respond to heat waves.  

Two specific activities that I will highlight today include the creation of a guidance document for the development of heat response plans and the development of a methodology for mapping urban vulnerability to the effects of heat waves. 

## Excessive Heat Events (EHE) Guidebook

- City-specific heat response plans
- The guidebook:
- EPA, NOAA, CDC, FEMA collaboration
- Options for defining EHE conditions
- How to assess local vulnerability
- EHE notification and response actions that work

**Notes:**
One critical lesson of previous investigations has been that excess mortality from heat waves can be prevented through the identification of relevant risk factors for a given locale and the development of written, city-specific heat response plans. 

Following this, CDC, in collaboration with colleagues at EPA, NOAA, and FEMA, have participated in the development of an Excessive Heat Events Guidebook, which provides a comprehensive set of guiding principle and a menu of options for cities and localities to use in the development of Heat Response Plans.  

These plans clearly define specific roles and responsibilities of government and non-governmental organizations during heat waves,  They identify local populations at increased high risk for heat-related illness and death and determine which strategies will
be used to reach them during heat emergencies. Heat response plans also include specific criteria for activation and deactivation
of the plan and measures for periodic evaluation of the plan.  

## Vulnerability Mapping using  Remote Sensing 

- _Objective:__ _
- “to develop a new research methodology that provides local and regional governments a new set of skills and tools in prevention and emergency response planning for acute and chronic urban climate impacts.”

**Notes:**
A second activity focused on adapting to the challenges of climate change and heat waves centers on a collaboration between CDC and the National Center of Excellence on Urban Climate and Energy at Arizona State University.  

This project’s goal is to develop a research methodology that provides local and regional governments a new set
of tools for prevention and emergency response planning for acute and chronic urban climate impacts. 

## Identify Vulnerable Neighborhoods

- Sorted spatially and temporally

**Notes:**
This approach attempts to understand the influence of built environment characteristics such as land use, housing stock and engineered materials on the spatial distribution of heat-related illness episodes, as quantified by EMS and Fire department dispatch data. 

This map of Phoenix Arizona shows the location of heat-related incidents for 2001-2005

## Layers of Vulnerability / Risk Factors 

**Layers include:**
- - Surface temp
- - Land cover
- - Power Outages
- - Demographic                                                                   	variables
- - Housing stock
- - Engineered 	materials

**Notes:**

This heat incident data can then be overlayed with other layers of known risk factors to predict which neighborhoods are more likely to experience heat-realted morbidity and mortality during heat waves.  

This will allow local emergency response personnel to not only focus resources during these events but to also tailor prevention and health communication messages to specific ethnic or demographic groups.

Prioirity areas for the provisioning of energy assistance and air conditioning can also be identified by this approach. 

## Composite Vulnerability Map

**Notes:**
Colleagues at King’s College London are producing similar composite vulnerability maps which display a graduated sensitivity to heat stress index by district.  This composite variable considers factors such as age, housing type, population density and poverty, but does not factor in the influence of the heat island effect through the use of satellite thermal imagery, as was shown in the previous work.   

We hope that future evaluations of these mapping techniques show that they are effective in predicting the location of deaths from heat waves and can prevent high mortality events like the one witnessed in Europe in 2003.   

## Final thoughts:

**Morbidity and mortality related to summer heat can prevented. **
**Adaptation measures such as city-specific Heat Response Plans are essential for prevention.**
**Epidemiologic studies and ecological models of risk provide important guidance for prevention efforts.**

**Notes:**
To conclude, it has become clear that the excessive temperatures brought about by climate change and enhanced by factors of the built environment cannot be prevented, but the high morbidity and mortality associated with these events can be.  

Public health can and should play an active role in the development of adaptation measures such as city specific heat response plans.

And finally, we should ensure that the development of these plans are guided by the best evidence based data, generated by epidemiologic studies and ecological models, on the relation between hazard and health outcomes.  

Thank you