1. Introduction
2. Introduction to Research Problem
2.1 Main Objectives
2.2 Research Problem
3. Overview of current status of research in Environment and Health
5. Research Methodology and Analysis
5.1 Data Processing
5.2 Data Analysis
6. References
Linking Environment and Health Using GIS: A Case study of Trans-Yamuna Area
The word environment literally refers to whatever surrounds an object or some other entity. Humans experience the environment in which they live as an assemblage of physical, chemical, biological, social, cultural and economic conditions which differ according to local geography, infrastructure, season, time of the day and activity undertaken (WHO, 1997a). The environment influences many aspects of human well-being and many diseases can be initiated, sustained, or exacerbated by environmental factors (Moeller, 1992).
Excessive and haphazard urbanization in our country has also contributed, in a major way, to the overall degradation of the environment in majority of Indian cities. The unrelenting movement of people from rural areas into urban centers has brought about a rapid evolution of cities into large metropolitan complexes. The result of this development has been an ever-increasing areal density of population and of industrial and commercial activities and consequently, the sources of pollution, now, more than ever, reside in close proximity to the potential receptors. In large cities, such as Delhi, millions of people may be exposed to severe outdoor air pollution. In addition, indoor air pollution is a widespread and serious problem particularly in developing countries. Worldwide, at least, a hundred million people are potentially affected by respiratory diseases associated with air pollution (WHO, 1992).
Human exposure to pollution in the air, water and food is a major contributor to increased health problems. The disease burden attributable to these exposures is not known with any degree of certainty. These exposures may be short-term - high level episodes, or longer-term - low level exposures. Exposure to environmental pollution is also usually involuntary and people may be ignorant of their exposure or its possible effects; as a result they may exert little or no control over exposure risks. High population density and the concentration of industry in rapidly growing cities have led to great pressures on the local environments resulting in a combination of increasing population and extreme poverty which tends to concentrate those with least opportunities in environmentally poor areas. It must also be remembered that many conditions involve a lengthy exposure or risk period, but each often has the underlying factor of poverty, which is itself a composite index of deprivation. It includes not only deprivation relating to economic resources but usually, too, access to education, social support, housing, environmental quality, nutrition and many other factors. Poverty remains the most significant predictor of urban morbidity and mortality. Thus, Poverty and environmental degradation are becoming more inextricably linked (Phillips and Verhasselt, 1994; WHO, 1997a).
It is evident, therefore, that there is a strong need to control harmful exposures. It is here, that the ability to link health and environmental data, and thereby to understand relationship between levels of exposure and health outcomes, becomes vital. Hence, the analysis of data on environment and health, as a basis for estimating the health impact of environmental degradation and setting priorities for action, remains an urgent need in many parts of the world and especially in the Mega-cities of India, where issues relating to environmental degradation have traditionally taken a second place to demands for economic development.
Analyzing the links between environment and health is, by its very nature, a spatial problem. Levels of risk vary geographically in response to variations in environmental conditions; health outcome and associated levels of need and health support vary as a consequence (Briggs, 1997). It is here that the geographical approach gains importance. "Analysis of the links between environment and health can be considered to comprise three main elements; first, the map generation for environmental risk and health outcome; second, map analysis; and third, map overlay and comparison. Each of these steps is amenable to, and can benefit from the use of GIS techniques" (Briggs, 1997).
The issues and concerns raised in preceding sections will be studied for a low income area of Delhi, which is under a serious environmental stress with a variety of health effects as a consequence. Delhi's population has been increasing very rapidly in recent years. Being 'landlocked', its areal extent cannot increase, with the result, there has been a steep rise in the density of population in certain regions of the city. This expanding population has put tremendous pressure on the existing facilities and infrastructure of the city and contributes towards environmental degradation and lowering of quality of life in general. The city suffers from numerous environmental problems such as those of pollution of air and water. Residents of low income areas suffer especially more due to lack of safe drinking water supply, which results in frequent outbreak of water borne diseases. Certain low income settlements are located close to solid waste disposal sites and water supply based on shallow handpumps becomes polluted especially in the monsoon season when the water table rises. The rise of small scale industrial units in non-conforming areas also adversely affects the general health conditions of inhabitants. Most of the low income settlements have a tendency to locate on cheaper and low lying areas (especially in Delhi) and waterlogging is a major problem during monsoon season, which again poses a grave threat to the exposed population to the dangers of vector borne diseases such as Malaria, Dengue, etc. Thus, TYA in Delhi is a problem area in terms of environmental conditions, infrastructure (including water supply, sanitation, waste disposal) as well as social aspects.
2. Introduction to Research Problem
Given the scenario (outlined in the paragraphs above), the study of environmental degradation exposure and resultant health outcome becomes relevant with the following objectives in mind:
It is important to note here that the objective is to assess exposure to environmental factors and to study the association between environmentally hazardous conditions and their health outcome; no attempt is being made to establish causal relationship between particular environmental hazard and a specific disease.
The current study proposes to explore the health impacts of environmental degradation, based on analysis of environmental exposure and health data using GIS, in the Trans-Yamuna Area of the Metropolitan City of Delhi. The study will employ certain environmental-health indicators, such as access to safe drinking water, infant mortality rate, housing related indicators, which convey the key issues and problems afflicting the study area. These issues and indicators are discussed in the following text.
Inspite of planned development efforts, majority of the Trans-Yamuna-Area (TYA) has not been developed in a planned manner; a great proportion of population is living in sub-standard conditions and is bereft of urban amenities, proper utilities and services. Compared to rest of urbanizable area of Delhi, Trans-Yamuna Area is approximately 11%, which accommodates approximately 20% of the population. Further, another feature of TYA is that about 15-20% of the area (of TYA) is being occupied by about 35% of the population, which indicates that the burden on land available in TYA is more than that of rest of Delhi. Many areas in the TYA are barely fit for human habitation. A huge chunk of population is currently living near environmentally hazardous sites, such as those of open drains (e.g., the Seelampur drain slum area) and solid waste disposal sites. Pollution of water resources due to poor sanitation infrastructure and dumping of industrial wastes threatens the water supply of the residents. Solid waste and air pollution have created similar threats to human health. Due to the fact that majority of the areas are low lying areas as such the required gradient for the flow of sullage water, drainage system and the drinking water is not available due to which these systems could not be made fully operational. Waterlogging is another major problem, especially in low-lying areas (mostly reclaimed land as well as sections close to banks of River Yamuna). These problems, coupled with low-incomes, massive unemployment, illiteracy, over crowding, etc are responsible for poor health status of people residing in this area. TYA is considered poorly developed in terms of planned orderly growth, sanitation, water supply, transport, housing, schooling, health, recreation, etc. in comparison to the rest of Delhi.
The Trans-Yamuna Area has approximately 166 JJ clusters, which is greater than any other comparable unit in Delhi. The density of population is extremely high, especially in the unauthorized colonies and JJ clusters, with a high migration rate, and to make matters worse, there is huge ‘floating’ population. There is inadequate provision of ‘safe’ drinking water, sanitation facilities are insufficient (a major proportion of population is without these benefits). There is an acute shortage of open spaces (green areas), and a relatively high crime rate. The morbidity and mortality rates are comparatively higher due to frequent and regular outbreak of various diseases (mostly water borne). The availability of health services is way below the levels considered acceptable; for example, the total number of beds in hospitals falling under TYA was only 1998. There were only 32 dispensaries in TYA and while the sanctioned strength of doctors in these dispensaries is 70, only 49 were in position. Therefore, the existing facilities are inadequate from both qualitative and quantitative point of view. Also, there is considerable heterogeneity in the population, both in terms of ethnic and economic environment and therefore, the impact on health of environment also varies. It is one of the objectives of this study to attempt mapping of these variations.
The lack of basic amenities, coupled with high density of population renders many sections of TYA vulnerable to environmental degradation, which inevitably results in poor health status of the exposed groups. Poor and those lacking opportunities are the worst affected groups. Often migrants choose environmentally hazardous areas, as they cannot afford a better location. They too constitute the exposed group. Proper understanding of the extent and nature of problems afflicting this area is imperative for any meaningful measures to correct the current situation. To effect this, identification of areas requiring special attention is crucial, so that these 'problem or high risk areas' can be tackled on a priority basis. These figures bring out some of the issues that plague this area. While the issues are clear, the extent and scale of problem remains to be ascertained. Thus the basic question of this research can be put as - "Is there an association between environmental conditions and the prevailing health status of the people residing in TYA, and if so, then which areas are the worst affected?"
2.3 Conceptual Issues Involved.
Exploration of associations between environment and health is an integral part of Environmental Epidemiology, either in the search for previously unknown relationships between environment and health, or to test hypothesis about such relationships. Linkage Analysis is an extension of this approach. It involves applying known exposure-response relationships, established in previous research and documented in the literature, to new empirical data as a basis for improved decision-making and policy support. Many methods are available for this purpose and for the present study, ecological analysis method has been chosen.
Ecological analysis involves the investigation of group-level relationships between environment and health, by analyzing spatial and/or temporal variations in exposure and health outcome. For the reasons of logistics and cost, it is also the most appropriate approach feasible, especially where a large population study (as in this case) is under consideration.
Provided the suitable exposure information is available, ecological analyses can be conducted in a number of different ways. One approach deals with the study of associations between spatial variations in exposure and disease outcome in a single population at a given point in time. Alternatively, relationships between exposure and health outcome can be compared in two or more populations that differ in terms of their exposure. In either of the two cases, the data typically refer to a relatively short span of time and there are no multiple measurements over an extended time period. A third approach is to analyze time-trends within an ecological design (Nurminen and Briggs, 1996). This study shall employ the second choice, i.e. the analyses of relationships between exposure and health outcome for different populations (identified according to the sub-zone, which has been taken as a unit of study) and plot the outcome on map showing differential rates of risks and impacts.
To identify and quantify the risks on health due to environmental pollution, use of environmental-health indicators is proposed. Environmental-health indicator has been defined as follows:
An expression of the link between environment and health, targeted at an issue of specific policy or management concern and presented in a form which facilitates interpretation for effective decision-making.
Two types of environmental-health indicators may be distinguished here:
The importance of environment-health relationship within the concept of environmental-health indicators is crucial. It is only through the knowledge of this link that an environmental indicator or a health indicator can be translated into an environmental health indicator. Thus, an environmental-health indicator is an environmental indicator or a health indicator plus a known environment-health relationship.
The link between environment and health operates through the exposure of humans to environmental hazards. However, health effects arise only if humans are exposed, at a specific place and during a specific time period (refer to figure-1). Also, it is important to realize that environmental conditions per se may become health threatening. Lack of access to safe drinking water, sanitation facilities, presence of industries in non-conforming areas, etc. constitute the harmful aspects of environment. Exposure occurs when humans encounter the contaminants within the environment. A range of health effects may then occur from minor-sub-clinical through illness, to death, depending upon the intrinsic harmfulness of the pollutant, the severity of exposure and the susceptibility of the individual concerned. The whole process is often driven by persistent forces which both motivate the creation of the hazard and increase the likelihood of exposure (WHO, 1996). Over the years, many attempts have been made to devise conceptual framework for indicator development. One of the most recent and accepted frameworks is the - DPSEEA framework (Driving Forces, Pressure, State, Exposure, Effects, and Actions).
Within this framework, the Driving Forces component (D) refers to the factors, which motivate and push the environmental processes involved. One of the most important of these is population growth. Other driving forces also exist such as technological development and economic development.
The driving forces within DPSEEA model result in the generation of Pressures (P) on the environment. These pressures are normally expressed through human occupation or exploitation of the environment. One of the most important components of pressure in the context of human health is clearly the release of pollutants in environment.
In response to these pressures, the State of the environment (S) is often modified. The changes involved may be complex and far-reaching. Thus changes may occur in the frequency or magnitude of natural disasters, availability and quality of natural resources; and in the levels of environmental pollution (e.g., air quality, water quality, quality of housing, etc). These changes in the state of the environment also operate at markedly different geographic scales.
As mentioned earlier, environmental hazards only pose risks to human well being when humans are involved. Exposure (E), thus refers to the intersection between people and hazards in the environment. It should be noted that exposure is rarely an automatic outcome of the existence of hazard.
Exposure to environmental hazards in turn lead to a wide variety of health Effects (E2). These may vary in type, intensity and magnitude depending upon the type of hazard to which humans have been exposed, the level of exposure and the number of humans involved. The earliest and the least intense effects are sub-clinical, involving some reduction in function or loss of well being. More intense effects may take the form of illness or morbidity. Under the most extreme conditions, the result is death.
In the face of effects, society typically attempts to invoke a range of Actions (A). The most effect long-term actions are those which are preventive in approach.
In the present study; emphasis shall be placed on the indicators at the exposure and effects position in the DPSEEA chain.
3. Overview of current status of research in Environment and Health.
Exposure of humans to pollutants in air, water, soil and food is a major contributor to increased levels of morbidity and mortality. A large number of studies have been conducted in the field of environmental epidemiology relating to exploration of links between environmental factors and hazards and their disease outcome. For example Dunn and Kingham (1996) have attempted establishing links between air quality and health. Traditional approach in environment spatial epidemiology has relied on assessing postulated links between environmental pollution and ill health. However, a combinational approach of using data for health and environmental factors (spatially referenced data) has been accepted as more satisfactory. Jenkins and Hay (1996) have worked on a similar theme by studying the combined effects of different pollutants found in the ambient air and their health effects. An interesting study by Frolich and Mustard (1996) A Regional Comparison of Socio-Economic and health Indices in a Canadian Province, explores the methodology for selecting and combining measures of an area’s socio-economic characteristics to produce a composite index which is relevant for health-related research. A study with similar theme Air pollution and Mortality in Valencia, Spain: A Study using the APHEA methodology by Ballester, Corella, Perez-Hoyos and Hervas (1996), assesses the short-term relationship between daily air pollution indicators and mortality in Valencia. This was an ecological study using time series data with application of Poisson Regression.
Spatial analysis and mapping in environmental health have a long history. It is now traditional to trace their origin back at least as far as the seminal study of John Snow on Cholera in London (1855). Until recently however, studies such as these could be carried out only manually. With the advent of GIS in market (a decade ago), this field has been revolutionized. These have made mapping and spatial analysis easier, quicker and more flexible. One example of this type of application is shown by the analysis of health outcome around point emission sources, for example studies by Hills and Alexander (1989) and Thomas (1991). However, much of this research has been done without GIS. Some recent work using GIS for spatial analysis (of health and environment) includes the study by Gatrell and Bailey (1996) Interactive Data Analysis in Medical Geography. This study considers the use of ARC/INFO, in a spatial analysis context, showing how the spatial analysis tools may be added on to the core module and exploited by medical geographers. Such tools include those for modeling possible raised incidence of diseases around suspected source of pollution. Another study by Sahay and Walsham (1996) Implementation of GIS in India: Organizational Issues and Implications explores the issues involved in use of GIS in Indian context. An article by Levine (1996) Spatial Statistics and GIS: Software tools to quantify spatial patterns discusses various packages available for spatial analysis.
Delhi, the capital has an area of 1483 km2 of which 685.34 km2 was categorized as urban and the rest as rural by census. However, this distinction seems meaningless in the context of the dominant framework of urban activities and communications in the territory (Nagpaul, 1988). Under the Master Plan for Delhi-2001, notified on 01-08-90, Delhi has been divided into 15 zones, 8 in Urban area (A-H), 6 in Urban Extension and Rural Area (J to N & P), and one, the river and the river front area (O). Trans-Yamuna Area (TYA), also known as Planning Zone (Division) - ‘E’, is located in the Eastern portion of National Capital Territory of Delhi across the river Yamuna, abutting Loni, Sahibabad and Noida Areas of UP. Total area of Trans-Yamuna Area, according to DDA Draft Zonal Plan document, is approximately 8797 hectares.
For the present study, Trans-Yamuna Area (TYA) of Delhi has been chosen to attempt an analysis of link between environmental degradation and its health outcome. The TYA is situated at the Eastern Bank of River Yamuna and much of the area was developed after re-claiming the land from the river. Since the majority of the land has been re-claimed from the river, they are mostly low-lying section (in comparison to other localities of Delhi). Trans-Yamuna Area, until 1960, had a very small inhabited area such as Shahdara. Even with the beginning of implementation of the Master Plan in 1962, Trans-Yamuna Area remained vacant except for some old development like Shahdara, Geeta Colony, etc. As per MPD-62, this area was planned for a balanced development to contain about 750,000 (0.7 million) persons. However, a large umber of unauthorized colonies developed on the Trans-Yamuna side due to its proximity to walled city CBD, CP and other central areas, as well as due to availability of cheap land (low lying areas under the danger of flooding during monsoon). Large sections, which were meant for recreational and other public facilities, were therefore, unauthorizedly encroached upon and the provision of civic amenities has not been able to keep pace with the development of the area. In the course of urban development and expansion during the last decade, the population has exceeded the figure of 2 million. Therefore, it need not be overemphasized that this huge population concentration, in such a limited area, has serious implications for the environmental state and the consequent health impacts. Therefore, after taking into consideration the issues and problems of the area (outlined in the preceding sections), the area was chosen for linkage analysis of environmental and health data, using the ecological analysis technique and GIS as a tool.
Linkage analysis involves the use of routinely collected data to derive environmental-health indicators. A major advantage of this approach is its cost-effectiveness. With the issues and problems of the Trans-Yamuna Area in perspective, data on the following aspects of environment will be collected:
Physical Health: Physical health data, which would include data on Morbidity, Mortality and Preventive healthcare, as well as the delivery of health care, shall be obtained from the Directorate of Health Services and other relevant agencies, including the local clinics (in case of intensive study of a selected environmentally hazardous area).
Based on the data acquired from the above-mentioned sources, various environmental-health indicators will be employed to assess the exposure to environmental conditions in the various sub-zones taken up in the present study. These indicators will relate to three major aspects - health, socio-economic conditions, and environmental conditions. For example some outcome (or effect-based) indicators are as follows:
Some examples of exposure (risk factor) based indicators include:
An intensive study of one selected location shall be conducted (after identification of vulnerable or environmentally hazardous areas) to further test the linkage/association between environmental conditions and health outcomes. This would entail a field survey of a representative (sample) population, say 100 households, chosen randomly, from a selected settlement for this purpose. Data relating to provision of basic amenties (such as sewerage, safe drinking water, solid waste disposal) and health condition of the people, i.e. the diseases that afflict the sample population, as well as provision of medical care shall be collected. To collect the abovementioned information, the questionnaire would include questions on (Some examples):
The precise sampling design for the study shall be decided subsequent to identification of critical areas. The data collected from the field survey shall be organised in a Relational Database Management System (RDBMS).
5. Research Methodology and Analysis
In the context of environment-health linkage studies, GIS offer a range of important capabilities. This study will employ Geographical Information System for map generation as well as some spatial data transformation and analysis. To date, the use of GIS in analyzing links between environment and health has been by comparison relatively limited (WHO, 1997b). They nevertheless have much to offer. In the present study, analysis of the links between environment and health shall comprise at least two main elements:
Generation of maps involves many activities. The first and the foremost involve porting of spatial information to digital format. This will be effected by scanning and subsequent digitization or direct digitization, if the facilities become available. This will be followed by preparation of attribute tables and linking of the data with AREA-IDs. However, generation of maps is not a simple activity and may involve the following issues:
All data processing will be computer based. Other relevant statistical techniques shall be employed as and when the required. Primary data shall be collected in accordance with the method mentioned in the 'sources' section. This would also entail the creation and maintenance of a Relational Database, which would later be integrated with the coverages prepared using the Geographical Information System, to facilitate further spatial analysis and complex query building.
Subsequent to production maps, data analysis stage concentrates on interpreting the results obtained from the processing of data. This stage would entail the preparation of aggregate tables, based on earlier data processing, identifying units where the environmental factors are critical and attempt an association with the prevalent health scenario. Spatial analysis, or to be more specific, Map overlay and comparison shall be performed to identify high risk or vulnerable areas. The main emphasis will be on identification of high-risk or critical areas. Methods of comparing environmental and health data depend to a large extent upon the measures of risk available. Where maps of pollution are available, it is clearly possible to compare these directly with outcome, using overlay method. (Briggs, 1997). However, where pollution or exposure has not been mapped, alternative indicators of risk may be employed, such as the location of the emission source (for example, the location of polluting industry). Overlay technique for identification of critical areas, using health and environmental data sets will be employed. Appropriate statistical and GIS techniques will be employed.
It should be noted that production of maps (subsequent to data processing) is not an end in itself. Attempt will also made to explain the existing patterns, to discover why the conditions, which are prevalent, are there at all. The next logical question which must be answered is how these conditions are affecting the health of inhabitants of given area. To this purpose, data collected through field survey will be utilized to explain the association between environmental hazards present in the selected settlement and its health outcomes. Suggestions for improvement of conditions shall also constitute a part of this proposed study.