Environmental Health Indicators
1.1 The role of indicators
There is an increasing need and demand for environmental health indicators, from agencies and practitioners to help support and monitor policy on environment and health at all levels – from the local to the international. Indicators are needed, for example.
- Monitor trends in the state of the environment, in order to identify potential risks to health;
- Compare areas or countries in terms of their environmental health status, so as to help target action where it is most needed or to help allocate resources;
- Assess the effects of policies or other interventions on environmental health;
- Help raise awareness about environmental health issues across different stakeholder groups (including policy-makers, health practitioners, industry, the public, the media);
- Investigate potential links between environment and health (e.g. as part of epidemiological studies), as a basis for informing health interventions and policy.
1.2 What makes a good indicator?
The development of good environmental health indicators is nevertheless challenging. To be effective, indicators must satisfy a number of different criteria. In order to meet the needs of their users, who are often not experts in the subject matter or the idiosyncrasies of the data, they must provide a relevant and meaningful summary of the conditions of interest. In order to satisfy the wider community – including those who might wish to challenge the message they give – they must be transparent, testable, and scientifically sound.
1.3 Implications for indicator design
The different uses to which indicators may be put – as illustrated by the list of potential applications, above – also creates challenges. Each use may imply the need for a slightly different indicator. An indicator devised to monitor trends over time, for example, should be based on data that are spatially representative, but not necessarily spatially intensive or complete. An indicator developed to raise public awareness about an environmental health issue will need to be interesting and acceptable to the community concerned (in the jargon of indicators it will need to have ‘resonance’). In devising indicators for use as part of an epidemiological.
The investigation, however, emphasis will be placed first and foremost on its scientific validity and accuracy.
For all these reasons, developing multi-purpose indicators is extremely difficult. All indicators are to some extent use-specific and context-bound.
What makes a good indicator at one place at one time will not necessarily be relevant at another. As a consequence, although it is possible to devise definitive indicator sets that serve specific needs (e.g. OECD 1998), the wider utility of these is inevitably limited. On the other hand, it is not appropriate simply to let a form of indicator anarchy – in which everyone develops their own indicators – prevail.
This would merely result in a large duplication of effort, the proliferation of indicator sets, and the growing difficulty of comparing or combining indicators from different sources. It may also encourage the development of poorly-conceived and ill-designed indicators which may misinform rather than inform. Instead, the need is for guidelines that can help users develop and construct their own indicators, which satisfy their own needs, yet at the same time meet high standards of design and validity. That is the primary purpose of the ‘Indicator Profiles’ presented here. Their aim is:
- Rationalize the way in which environmental health indicators are formulated, constructed, and applied;
- Provide clear guidelines on indicator design;
- Encourage clear and full documentation on the genealogy of indicators;
- Awareness and consideration of the limitations inherent in the indicators; and
- Good practice in indicator construction and interpretation.
To this end, the profiles describe a sample of environmental health indicators and show how they can be compiled and interpreted. The descriptions, however, provide a useful framework that should be relevant for many applications.
- ORGANISATION OF THE INDICATOR PROFILES
The environmental health issues for which the indicator profiles have been developed are not to be defended in terms of their global importance or political priority. On the whole, the issues used are of widespread significance, but as noted above – and as the recent development of National Environmental Health Action Plans (Briggs et al. 1998) show – environmental health priorities vary markedly from one country to another. Major differences in priority occur, in particular, between the less developed and more developed areas of the world (WHO 1992, 1999). Indeed, one of the main messages to draw from the profiles is the need always to interpret indicators, and the issues to which they relate, holistically: to see them within the wider context.
In light of this, the issue-related indicators presented here are preceded by two introductory sets of indicators, relating to the socio-economic and policy contexts. The purpose of these is to provide a description of the wider realm within which the issues exist and to provide background information that can be used to help interpret the issue-specific indicators.
It should also be mentioned that the definition of environmental health issues is, in itself, a complex task. The way any issue is defined and approached is likely to vary substantially depending on the perspective of those.
2.2 The DPSEEA framework
The indicators are arranged in terms of the now widely-used DPSEEA framework (Figure 1) (Corvalán et al. 1996). Within this framework, the component of the driving force (D) refers to the factors which motivate and push the environmental processes involved. Of these, possibly the most important is population growth; others include technological development, economic development, and policy intervention.
The driving forces within the DPSEEA model result in the generation of pressures (P) on the environment. In each case, pressures arise at all stages in the supply chain – from initial resource extraction, through processing and distribution, to final consumption and waste release.
The changes involved may be complex and far-reaching, affecting almost all aspects of the environment and all environmental media. These changes in the state of the environment also operate at markedly different geographic scales. Many others are more widespread, contributing to regional and global environmental change (e.g. desertification, marine pollution, climate change). Because of the complex interactions which characterize the environment, almost all these changes have far-reaching secondary effects.
Exposure (E1) thus refers to the intersection between people and the hazards inherent in the environment. The National Academy of Sciences (1991) defines exposure as ‘an event that occurs when there is contact at a boundary between a human and the environment with a contaminant of a specific concentration for an interval of time’. In the case of environmental pollution, therefore, exposure can occur in a number of different ways — by inhalation, ingestion, or dermal absorption — and may involve a wide range of different organs. External exposure refers to the quantity of the pollutant at the interface between the recipient and the environment.
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Since using some form of the personal monitor (e.g. passive sampling tubes for air pollution) or by modeling techniques (e.g. based upon knowledge of concentrations in the ambient environment). . Target organ dose refers specifically to the amount that reaches the human organ where the relevant effects can occur (Sexton et al. 1995).
Exposure to environmental hazards, in turn, leads to a wide range of health effects (E2). These may vary in type, intensity, and magnitude depending upon the type of hazard to which people have been exposed, the level of exposure, and the number of people involved. For convenience, a simple spectrum of effects can often be recognized. The earliest, and least intense, effects are sub-clinical, merely involving some reduction in function or some loss of wellbeing. More intense effects may take the form of illness or morbidity. Under the most extreme conditions, the result is death.
It must be said that the DPSEEA framework works well for risks associated with environmental pollution, where the chain from driving force to source activity and thence to health effect via emissions and exposure is evident. Therefore It is less appropriate, however, in the case of physical risks, as presented by natural hazards (e.g. flooding) or technology (e.g. traffic accidents), where the concept of ‘pressure’ is less meaningful.
Some are more source-based (i.e. focusing on the driving forces and pressures that lead to exposure); many are exposure-based; others are an effect- (i.e. health-) based.
2.3 Structure of the profiles
The indicator profiles are designed to provide a range of information on the indicators. The profiles are divided into two sections:
- Hence a general Indicator Profile, describing the environmental health issue which the indicator addresses, the rationale and role behind the indicator, linkage with other indicators (within the set described), alternatives methods of defining and constructing the indicator, related indicators (proposed or developed in other, international programs), sources of further information, and relevant agencies involved in indicator development and use.
- An Example Indicator, giving a specific definition, relevant underlying concepts, data needs and sources, method of computation, units of measurement, potential scales of application, and guidelines on interpretation.
The full set of indicator sheets is hosted on the Web, at the address:
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Briggs, D.J., Stern, R.M. and Tinker, T. (eds.). 1998. Environmental health for all. Risk assessment and risk communication in National Environmental Health Action Plans. Dordrecht: Kluwer, 278 p.
Corvalán, C., Briggs, D. and Kjellstrom, T. 1996. Development of environmental health indicators. In: Linkage methods for the environment and health analysis. General guidelines. (D. Briggs, C. Corvalán and M. Nurminen, eds.). Geneva: UNEP, USEPA, and WHO, pp.19-53.
National Academy of Sciences.1991. Human exposure assessment for airborne pollutants. Advances and opportunities. National Academy of Sciences, National Academy Press, Washington, D.C., USA. 321 p. OECD. 1998. Towards sustainable development. Environmental indicators. Paris: OECD.
Sexton K, Callahan MA, Bryan EF. 1995. Estimating exposure and dose to characterize health risks: the role of
human tissue monitoring in exposure assessment. Environmental Health Perspectives, 103(S3), pp. 13-29.
WHO. 1992. Our planet, our health. Geneva: WHO.
WHO. 1999. The global health report. Geneva: WHO.