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This review will provide better insight into developing and validating a heat vulnerability assessment tool for Pakistan.
Methods
A literature search was done to identify studies onon heat vulnerability assessment published from January 2012 to January 2021 (10 years). Online databases PubMed, Google Scholar, Scopus, and Web of science were used for the literature search.
Results
Heat vulnerability can be evaluated by some specific determinants that have heat-related health events, including social, economic, environmental, housing, and geographical factors.
Conclusion
This tool will identify heat vulnerability risks and mitigate morbidity and mortality.
Global warming and rapid change in climate during the past few years have been a challenge to the world, bringing several changes in the nature and atmosphere on the planet.
Climate change includes droughts, unusual rainfalls, the melting of glaciers, and an increase in temperature. The rise in extreme heatsignificant is one of climate change's significant outcomes.
The increasing heat intensity is a substantial risk to human health and life. This extreme heat is a health hazard and continues to grow as a disease burden during the past few years. A significant number of deaths have been reported in different parts of the world due to heat vulnerability.
Extreme heat is defined as much hotter and more humid than average. In some parts of the world, the temperature is raised to the extreme during the summers, especially.
Excessive heat harms health & well-being and can cause dehydration, acute cerebrovascular accidents, blood clots, and death. Moreover, the literature reported that heatwave caused multiple emergency hospitalizations, which turned into cardiovascular, respiratory, and renal failure.
According to World Health Organization (WHO 2017), during the last 15 years, the number of people exposed to heat reached 125 million globally, and around 1.7 million people died due to its intensity, of which 70000 belong to Europe.
A multi-country study in 400 communities from 18 countries, including countries from Asia, Europe, and North America, reported an excessive surge in deaths during the last two decades due to heat vulnerability. The reported number of deaths ranges from 30000 to 1 million, which determines that this number will keep increasing in coming years and affect every individual around the globe.
South Asia is the most densely populated region in the World and most prone to natural disasters. High poverty and food insecurity make South Asia vulnerable to climate change. Some parts of the region face extreme heat, and temperatures rise to 50° Celsius
Research reported an extreme heatwave caused 2500 deaths in India in May 2015 with a temperature rise greater than 40° Celsius. Andhra Pradesh and Telangana were the most affected regions.
Climate change and vulnerability due to heat vary in different parts of the world. Studies suggested that each year with the change in the climate globally, heat vulnerability will continue to cause health disparities and deaths to increase up to 3 fold.
Crops do not sustain and grow properly in low or extreme temperatures. Many of the countries in Asia and Africa sustain their economy through agriculture. If they cannot grow crops well, the export will be low and causing economic instability.
Health system readiness and public health measures are required to tackle this issue. The occurrence of extreme heat events will continue in the future as predicted, ultimately leading to the burden of disease. Contextual preparation to tackle heat events is needed in communities. The adverse health consequences and vulnerability due to heat can be prevented by taking certain measures and developing a mechanism that can empower an early warning system.
By measuring heat vulnerability in resource-limited areas like Pakistan, stakeholders can target resources to zones and individuals at high risk of heat vulnerability.
Heat vulnerability can be evaluated by some specific determinants that have heat-related health events, including social, economic, environmental, housing, and geographical factors. These elements can be determined through available literature concerning field experts and related research. Different methods are applied to determine and understand heat vulnerability in the available literature, and extensive research has been conducted; therefore, it is important to review and compare this literature for developing a heat vulnerability assessment tool.
This review will provide better insight into developing and validating a heat vulnerability assessment tool. It has included 12 studies that have used different methods, variables, and analyses to construct heat vulnerability tools. Moreover, the limitations of these tools were also highlighted.
2. Methods
A literature search was done to identify studies on heat vulnerability assessment published from January 2012 to January 2021 (10 years). Online databases PubMed, Google Scholar, Scopus, and Web of science were used for the literature search. “Heat, high temperature, extreme temperature, heat waves, vulnerability, assessment, tool, index, risk, hazard, geography, geospatial, and GIS” were search terms used individually and in combination as inclusion criteria for literature to be considered for this review. Only English-language peer-reviewed articles mentioning the “development of heat vulnerability assessment tool/index” were considered.
3. Results and discussion
The characteristics of 12 studies (Fig. 1) included in this review are summarized in Table 1, which includes author, year of publication, study location, variables, and methods used in those studies.
Pre-existing illness, census data, population density, housing density, normalized difference vegetation, education, nature of housing material, water availability, and minority status.
Socio-demographic, environmental, health-related variables and temperature level were the most common variables studied to determine the association with heat vulnerability in these articles for the development of the heat vulnerability assessment. These factors were broadly studied and explained in the literature, showing a significant agreement with heat vulnerability.
Age, poverty, language barrier, race, and social isolation were the major socio-demographic determinants examined to understand the association with heat vulnerability.
The correlation between an individual's health problems, including cardiovascular disorders, diabetes, asthma, obesity, and mental status with heat vulnerability, was also checked in certain studies.
Environmental-related factors such as humidity, air temperature, radiant heat, heat sources, exposure to the sun, land surface temperature, and workload duration and severity were also checked for an association with health vulnerability assessment.
Other than these factors, mapping temperature level, climatic change severity, land surface temperature, housing density characteristics, housing density, and building age were looked to develop a health vulnerability assessment tool.
Socio-economic and demographic data have been essential indicators for heat vulnerability in different research. These indicators identify an individual's characteristics to establish the association with any health-related event. Age, race, and ethnicity are notable characteristics to understand the problem. Malik SM et al. reported that climate change daffected the population with low socio-economic status, and improving the socio-economic conditions can reduce heat vulnerability.
Johnson DP., et al., mentioned in their findings that socio-economic status is highly correlated with morbidity and mortality due to extreme heat. Heat vulnerability causes health hazards to the population below the poverty line.
Children and old people are at potential risk of heat vulnerability. The elderly's body response to heat is relatively poor than the young age group, and chronic illness is another risk factor for the elderly. Children are also susceptible to extreme heat; they also have a weaker body response to extreme heat.
People with low socio-economic status, poverty, and social isolation/living alone are also at a greater risk of heat vulnerability because their ability to mitigate this risk is deprived. The low socio-economic class is majorly laborers, and they work in hardships for financial sustainability. They lack social and financial support to mitigate the risk of heat vulnerability.
Nayak, S. G., et al., reported in his findings that unemployment, poverty, disability, language barrier and black race were at risk of vulnerability due to extreme heat, and these conditions were highly correlated with the morbidity and mortality due to heat vulnerability in findings of Zottarelli LK et al.
3.3 Pre-existing illness/health conditions
Pre-existing health issues cause more adverse health effects, combined with heat vulnerability. Azhar G et al. reported that respiratory and cardiovascular disorders were significantly associated with heat vulnerability, and hypertension is a significant risk factor for heat vulnerability.
However, Christenson M et al. mentioned in their findings that not only respiratory and cardiovascular disorders but individuals with diabetes, obesity, and mental status are also susceptible to heat vulnerability.
Literature has reported that the relative mortality risk due to heat vulnerability was 23% higher in patients with circulatory system disorder and chronic obstructive pulmonary disease (COPD) compared to the non-disease group.
The influence of pre-existing health conditions on short-term mortality risks of temperature: evidence from a prospective Chinese elderly cohort in Hong Kong.
Zuhra SS et al. also reported the same finding, pre-existing illness (diabetes) increased the susceptibility of an individual to heat vulnerability due to impaired thermoregulation.
Appraisal of the heat vulnerability index in Punjab: a case study of spatial pattern for exposure, sensitivity, and adaptive capacity in megacity Lahore, Pakistan.
It is understood from the available literature that these pre-existing health conditions cause the human body's response to slow and weak to such stresses, making them a high-risk population for heat vulnerability.
3.4 Environmental and thermal characteristics
Environmental and thermal characteristics such as the magnitude of temperature, humidity, air temperature, exposure to the sun, and land surface temperature (LST) were extensively studied in the literature available and have great agreement with heat vulnerability, especially in the urban heat-related vulnerability.
Cai, Zhi et al. used LST as an indicator and measured it on exposure, severity, and adaptability to determine heat vulnerability. The findings mentioned that the heavy industrial area has the highest temperature and is most vulnerable to high exposure, severity, and adaptability to heat waves. Moreover, rapidly developing areas and urban areas cause an increase in LST in different megacities of China.
Christenson M et al. mentioned in their findings that extreme temperatures and low humidity were associated with mortality. Further added, increased air surface temperature, air pollutants, and no or less vegetation have caused extreme temperature. People living in neighborhoods without greenery are at high risk of heat vulnerability.
Malik SM et al. reported that agro-ecological zones in Pakistan encounter extreme temperatures, particularly during the summers, which put farmers and the labor workforce working in these agro-ecological zones at high risk of heat vulnerability.
Moreover, the coping power from the extreme heat of this workforce is low due to higher age and the unavailability of nearby health services.
A similar finding was reported by Laranjeira K et al., which added that the magnitude of the temperature, along with other environmental factors, increases the susceptibility and an individual's behavior and response towards it helps to cope with it. Urbanicity was a significant component of the failure of an individual's response toward heat vulnerability. The urban population faces extreme temperatures due to industrialization, polluted air, poor air quality, sedentary lifestyle, and poor water and food resources cause health hazards.
Along with socioeconomic, demographic, environmental, and thermal characteristics, housing and building characteristics were important indicators for heat vulnerability. Indoor heat exposure is a potential cause of vulnerability for women, children, and old people. Construction type and material play an important role in indoor heat exposure. Brick walls keep indoor temperature maintained. Shade on exterior areas stops increasing indoor temperature. Ventilation and air condition availability maintain thermoregulation and reduces indoor heat. These characteristics make a housing scheme suitable for living.
Samuelson H et al. looked at the association of different housing and construction characteristics with heat vulnerability, including construction & housing type, building material quality, ventilation, and air condition status. They found that housing schemes that fail to construct houses and buildings without proper ventilation, use of quality material and effective cooling system are at high two-fold risk of vulnerability due to extreme heat.
Zuhra SS et al. added that the availability of green spaces in housing shames and buildings works as a thermoregulator and maintains indoor/outdoor temperatures. In urban areas, it provides great relief from extreme heat. Other than this, population and housing density contribute to heat vulnerability. The denser population and housing cause -trapping and doesn't allow wind to pass, resulting in vulnerability to heat.
Appraisal of the heat vulnerability index in Punjab: a case study of spatial pattern for exposure, sensitivity, and adaptive capacity in megacity Lahore, Pakistan.
3.6 Development and validation of pre-existing tools/indexes
For developing a heat vulnerability assessment tool, it is essential to understand the development and validation of the pre-existing tools/indexes, methods used for analysis, and limitations of existing research. The articles added in this review specified the objectives of the construction and validation of these tools. Keeping these objectives in mind, an extensive literature search was done to determine the variables. The objectives were divided into two major categories, the first was to explore and validate the indicators for heat vulnerability,
Appraisal of the heat vulnerability index in Punjab: a case study of spatial pattern for exposure, sensitivity, and adaptive capacity in megacity Lahore, Pakistan.
For validity and to understand the correlation and association, statistical tests and models were used, and many articles mentioned the use of principal component analysis (PCA).
Factor analysis, z-scores, and weighted & un-weighted averages were other statistical techniques used to obtain results using the heat vulnerability index. Further to the validation of the pre-existing tools most common validity and reliability measures used were content validity index (CVI) and Cronbach alpha.
The results of these articles are explained in detail above, and the results were significant in terms of indexing heat vulnerability.
Most of the articles informed which socioeconomic and demographic characteristics describe heat vulnerability in a better way. Other reported health effects due to the exposure and severity. At the same time, rest identified environmental, housing, and building characteristics to be important in understanding heat vulnerability. One of the articles defined the consequences of rapid urbanization causing extreme heat.
3.7 Limitations of pre-existing tools/indexes
Despite the significant results, there are certain limitations in every research. The limitations reported by these papers were grouped into four categories. The first was specific to the certain characteristics, the other was related to data, the third. The first was specific to certain characteristics, the other was related to data, the third was regarding the associations, and the final was related to validity and bias. The limitation regarding the change of some variables especially socio-economic and environmental, with the passage of time was a significant one.
Appraisal of the heat vulnerability index in Punjab: a case study of spatial pattern for exposure, sensitivity, and adaptive capacity in megacity Lahore, Pakistan.
The determinants required to construct a heat vulnerability assessment tool listed by different research papers are important, for developing a heat vulnerability assessment tool, it will be difficult to consider all of them. The development of a heat vulnerability assessment tool for Pakistan can be done using factors that are essential and required for the population of Pakistan. Considering the most suitable determinants from these categories as reported in the existing literature, i.e., geographical location, socio-economic status, exposure & severity to heat, environmental conditions, and housing factors, a heat vulnerability assessment tool should be developed and validated in different parts of Pakistan which helps in identifying heat vulnerability to risk mitigate the risk of morbidity and mortality.
Ethical approval & informed consent
Not Applicable.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.
Availability of data & materials
Not Applicable.
Author's contribution
SS- Conceptualization, Methodology, Data Curation, Writing, Reviewing, and Editing.
SM- Writing, Reviewing, and Editing.
Declaration of competing interest
The author declares no competing interests.
Abbreviations
HVI
Heat Vulnerability Index
PCA
Principal Component Analysis
WHO
World Health Organization
References
Perkins-Kirkpatrick S.
Gibson P.
Changes in regional heatwave characteristics as a function of increasing global temperature.
The influence of pre-existing health conditions on short-term mortality risks of temperature: evidence from a prospective Chinese elderly cohort in Hong Kong.
Appraisal of the heat vulnerability index in Punjab: a case study of spatial pattern for exposure, sensitivity, and adaptive capacity in megacity Lahore, Pakistan.
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