(introduction...)

Human health is influenced not only by the physical environment, but also by social and economic factors. Traditionally, it has been the practice to include health-related risks as part of EIA studies. However, it is being increasingly recognized that a more comprehensive and rigorous approach needs to be adopted to identify and appraise those environmental factors which may affect human health, in the form of an environmental health impact assessment (EHIA). The various factors influencing human health can include geology, vegetation, demography, economics, pollutants, as well as the availability of health services.

The World Health Organization (WHO) has undertaken a great deal of fundamental research on EHIA, holding regular seminars, publishing documentation, and developing methodologies.

9.5.1 Need for EHIA

The WHO has identified a number of reasons for the need to undertake an EHIA. They include: prevention is better than cure, as with other forms of assessment; it is specified in many forms of EIA legislation; environmental degradation is linked to health impacts; the methodology can be incorporated in EIA; systematic inclusion of health impacts improves the legitimacy of the decisions made and the process by which they are taken; human health issues often prompt a public response and/or involvement; and there is no argument against it!

Although the need for EHIA is self-evident and is clearly spelt out by the WHO, there are some inherent difficulties in undertaking an EHIA: lack of baseline data on humans in local communities; the timescale for health effects to show up is very long; the interaction of different chemical, physical, and biological agents, their synergistic/antagonistic effects, etc., make it difficult to isolate the individual agent or group of agents responsible for the adverse impact - in other words, a clear cause/effect relationship is difficult to determine; the variety of human responses and exposures; limited knowledge of dose-response relationships; and planners and decision makers may feel that health is not their responsibility.

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Given that health impacts need to be addressed and integrated in EIA studies, and they often are not given sufficient attention or analysis, the question then becomes "What methodologies and/or approaches exist that might be used to facilitate the integrated consideration of health impacts?''

9.5.2.1 Adapt EIA study activities

Adapt the typical activities in an EIA study (listed below) to systematically include attention to health impacts.

(i) Preparation of description of projects.
(ii) Review and analysis of pertinent institutional information.
(iii) Identification of impacts.
(iv) Description of effected environment.
(v) Predictions of impacts.
(vi) Interpretation of predicted impacts.
(vii) Identification and evaluation of mitigation measures.
(viii) Selection of proposed action.
(ix) Written documentation.
(x) Monitoring of environmental impacts.

9.5.2.2 Integrate health impacts into EIA

Integrate an existing health impact methodology into the typical activities in an EIA study or use the health impact methodology as the focus of the EIA study. To serve as an example, a generic methodology for EHIA has been suggested by the WHO. It consists of the nine steps listed in Table 9.11. Steps 1 and 2 are related to the normal EIA process in which primary, secondary, and tertiary impacts on environmental parameters are assessed. Step 3 is derived from information given in the EIA and for which environmental health factors can be identified. Methods for identification of environmental health factors could be based on epidemiological and/or toxicological evidences of causal links between environmental parameters and health effects. Step 4 involves the study of exposure pathways. Steps 5 and 6 use epidemiological and toxicological information on dose-incidence and dose-response relationships between environmental parameters and specific health effects. Step 7 can be used to evaluate significance and acceptability of adverse health effects, and step 8 focuses on mitigation measures. Finally, step 9 involves appropriate decision-making. This generic EHIA methodology has been modified to allow its use for chemical manufacturing facilities.

Table 9.11 Steps in EHIA methodology

Item number	Steps to be taken	Tools to be used
Step 1	Assessments of primary impacts on environmental parameters	Regular impact assessments process
Step 2	Assessments of secondary and tertiary impacts on environmental parameters	Regular impact assessments process
Step 3	Screening of impacted environmental parameters of recognized health significance (EH factors)	Epidemiological knowledge
Step 4	Assessments of the magnitude of exposed population for each group of EH factors	Census, land use planning
Step 5	Assessments of the magnitude of risk groups included in each group of exposed population	Census
Step 6	Computation of predicted health impacts in terms of mortality and morbidity, if possible	Results from risk assessments studies
Step 7	Definition of acceptable risk (or of significance of adverse health impacts)	Assessments of trade off between human and economic requirements
Step 8	Identification of mitigation measures to prevent or reduce significant adverse health impacts	Abatement of EH factors? Magnitude reduction of exposure, reduction of exposed populations, protection of risk groups
Step 9	Final decision on whether or not the project should proceed

Source: Giroult, 1988, WHO Interest in EHIA, In: Wathern, P. (Ed.) Theory and Practice, Routledge: London.

9.5.2.3 Use a targeted approach

A targeted approach can be used, in which one or more empirical indices depict the relative health-related concerns associated with pollutant emissions (e.g., stress related to physical, chemical, biological, and/or radiological emissions), environmental transport and their pathways, environmental media contamination potential, and/or potential remediation measures and their effectiveness in reducing existing contamination.

Information on other targeted approaches is also available. These results of targeted approaches could then be integrated into the appropriate activities associated with the EIA study.

9.5.2.4 Probabilistic risk assessment

A probabilistic risk assessment can be conducted using the four major steps typically associated with health-related risk assessments; these steps include hazard identification, dose-response assessments, exposure assessments, and risk characterization.

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Considering the above methodologies or approaches in terms of their advantages and limitations, including such issues as data and personnel requirements and scientific credibility, it was determined that an integrated health impact prediction and assessment methodology should be based on an amalgam of selected features of each methodology or approach. A generic methodology will be effective only if it can take account of the broader policy-making context represented by the EIA process.

Figure 9.7 shows a flow diagram of the generic health impact prediction and assessment methodology. Each of the boxes represents an EIA activity, with the three activities representing the fundamental functions of the EIA process enclosed in a larger box. The activities corresponding to the description of the project and the environment are represented in the same box because in a health impact assessment they serve the same purpose. Information related to the description of the project and the environment can be used to identify and predict impacts.

9.5.3.1 Determining the need for health impact assessment

A preliminary task involves determining whether or not a health impact assessment is necessary. This task should consider in broad terms whether the possibility exists that health impacts will result from the proposed action. To conduct this task, potential health impacts should be analysed according to the nature of agents that may cause them. Depending on whether the agent is a chemical, a radionuclide, an organism, or a physical phenomenon, health impacts can be classified in the following categories: (1) chemical health impacts, (2) radiological health impacts, (3) biological health impacts, and/or (4) physical health impacts.

Figure 9.7 Conceptual framework for health impact prediction and assessment methodology

Source: Arquiaga, M. C., Canter, L. W., Nelson, D. I. Integration of health impact considerations in enviromental impact studies. Impact Assessment, Vol. 12, No. 2. 1994, p. 175-197.

If the need for a health impact assessment is shown, then a more exhaustive analysis of the health effects that could result from the project should be conducted. This analysis may start with the review and analysis of pertinent institutional information, which should be conducted prior to an extensive effort in an environmental impact study. The identification of pertinent legislation or regulations that address health effects should provide information helpful for one or more of the three analytical functions in the EIA process. The main use of institutional information will be for the interpretation of health impacts.

The task of describing the proposed action and its alternatives, and the environmental setting that will be affected, is the next activity in the methodology. The information related to the description of the project and the environment serves two purposes. The first is to identify project components and/or environmental features that may give rise to health impact concerns, and to use these to identify specific health impacts likely to occur. The second purpose is to record information regarding the project and the environment that may be useful in predicting (quantifying where possible) the identified health impacts.

9.5.3.2 Identify health impacts

Identifying health impacts is approximately equivalent to the hazard identification component of a conventional health risk assessment. It consists of determining whether exposure to the elements of the project and/or the environment may or may not cause a change in the incidence of a health condition. This activity, which may require an extensive review of information regarding human and animal studies, also involves identifying the nature of the health condition affected, if any, and the evidence that such a condition occurs in humans. The nature of the health condition affected should include not only the description of the condition, but also the classification of the potential impact in terms of its adverse/beneficial, reversible/irreversible, short-term/long-term, direct/indirect, and cumulative characteristics. These classifications, besides being important for the identification of health impacts, are relevant to their interpretation.

Another task associated with the identification of health impacts is that of defining those circumstances or scenarios, for example, routine operations versus accidents, under which health impacts may occur. This task provides a basis for assessing potential human exposure to the health impact causing agents. Examples of health hazards associated with various development projects are given in Table 9.12 parts (a) to (f), which may be used as guidelines during screening of projects for their potential health impacts.

9.5.3.3 Prediction of health impacts

The prediction of impacts represents the key technical steps in the EIA process, with qualitative information needed on types of impacts and quantitative information needed on unit impact factors and/or relevant impact models. Prediction methods are being improved as their predictive capabilities are verified and new technology and scientific knowledge become available. Since risk assessments techniques represent the state-of-the-art for the prediction of health effects resulting from environmental insults, and since these techniques are being extensively used in several regulatory areas, this generic methodology incorporates the use or adaptation of existing risk assessments techniques for the prediction of health impacts.

Table 9.12(a) Mining and mineral processing: screening for health hazards

Project	Health hazards	Causes
Location	Malnutrition	Loss of common property resources
	Vector-borne disease	Endemic disease foci
	Poisoning	Pollution from spoil deposits
Planning and design	Dust-induced lung disease	Excessive dust
Construction	Poisoning, injury	Inadequate occupational safety measures
	Communicable disease	Poor sanitation, poor water supply, poor food hygiene
	STDs	Labour camps
	Vector-borne disease	Exposure to vectors in endemic disease foci
Operation	Dust-induced lung disease, infectious respiratory disease	Poor protection from dust, poor ventilation
	STDs	Labour camps, unaccustomed wealth, poor health education
	Injury, poisoning, deafness, drowning	Poor occupational safety, abandoned mine workings, dam failure

Table 9.12(b) Coastal zone development: screening for health hazards

Project stage	Health hazards	Causes
Location	Malnutrition	Loss of common property resources by fisher folk
	Poisoning and excreta-related disease	Water-based pollution
Planning and design	Poisoning and excreta-related disease	Effluent disposal
Construction	Poisoning, injury, miscarriage	Inadequate occupational safety measures
	Communicable diseases associated with poor living conditions	Poor sanitation, poor water supply, poor food hygiene
	STDs	Labour camps
Operation	Injury	Storm and flood
	Poisoning and excreta-related disease	Pollution

Table 9.12(c) Thermal power: screening for health hazards

Project stage	Health hazards	Causes
Location	Injury	Fire, explosion, road haulage of fuel
	Respiratory disease	Air pollution
	Excreta-related disease	Use of contaminated water supplies following loss of water sources
Planning and design	Injury	Traffic routing
	Heavy metal poisoning	Fly ash disposal, leachates
Construction	Poisoning, injury	Inadequate occupational safety measures
	Communicable diseases associated with poor living conditions	Poor sanitation, poor water supply, poor food hygiene
	STDs	Labour camps
Operation	Respiratory disease, eye disease, injury, cancers, deafness	Air pollution, fly ash, explosion, noise, and vibration

Except for the prediction of health impacts involved caused by mechanical effects, which are generally predicted by extrapolating statistical data from similar types of actions, the risk assessment techniques for assessing the effects of the four categories of health impact causing agents considered in this generic methodology are similar, in that all consist of four well-defined steps. These steps (which in existing risk assessment techniques are hazard identification, dose-response assessments, exposure assessments, and risk characterization) could be perceived as health impact identification, dose-response assessments, exposure assessments, and health impact characterization when they are integrated in the EIA process.

The first step, which consists of establishing the relationship between a suspected health impact causing agent and a health condition, was described earlier. The dose-response assessment, which is closely related to the health impact identification, consists of describing the relationship between the dose of the health impact causing agent and the predicted occurrence of a health effect in an exposed population. The health effects that may result from exposure to health impact causing agents may fall into two categories: (1) those for which a range of tolerance exists in which no health effects are observed; and (2) those for which any dose is able to cause the health effect. For the former category, a threshold is typically defined that determines the upper level of the tolerance range. For the latter, a value defining the probability of incremental risk per dose unit is calculated. Depending on the nature of the health impact causing agent and the scenario defined for this agent, one or both types of dose-response relationship can be defined for a particular health impact causing agent.

Table 9.12(d) Highways and roads: screening for health hazards

Project stage	Health hazards	Causes
Location	Vector-borne disease	Endemic disease foci
		Access to forested hinterlands
	Malnutrition	Loss of common property resources, increase in land values, change of livelihood
Planning and design	Injury	Roads with poor safety features
	Communicable disease	Burrow pits, pooling, interrupted surface flows
Construction	Poisoning, injury	Inadequate occupational safety measures
	Communicable diseases associated with poor living conditions	Poor sanitation, poor water supply, poor food hygiene
	STDs	Labour camps
	Vector-borne disease	Exposure to vectors in endemic disease foci
Operation	Vector-borne diseases	Roadside squatters using
	Communicable diseases associated with poor living conditions	surface water supplies
	Respiratory disease	Dust
	Injury	Poor vehicle and road maintenance, poor traffic regulation, poor driver education, increasing vehicle density
	STDs	Long distance truck drivers

Table 9.12(e) Ports and harbours: screening for health hazards

Project stage	Health hazards	Causes
Location	Malnutrition	Loss of communal fisheries
	Poisoning	Leakage of hazardous materials during transit
	Excreta-related diseases	Poor waste disposal facilities
Construction	Poisoning, injury	Inadequate occupational safety measures
	Communicable diseases associated with poor living conditions	Poor sanitation, poor water supply, poor food hygiene
	STDs	Labour camps
Operation	Exotic communicable diseases, including bubonic plague	Accidental shipment of infected rodents, vectors, or pathogens
	STDs	Transit of single males
	Injury	Poor operation and maintenance

Table 9.12(f) Urban development: screening for health hazards

Project stage	Health hazards	Causes
Location	Communicable diseases associated with poor living conditions	Displacement through slum clearance, excreta disposal, water supply
	Injury	Steep hillsides, flood-prone valleys, poor access to and for emergency services
	Non-communicable disease	Pollution, hazardous waste, hazardous occupation
Planning and design	Excreta-related disease, vector-borne disease	Water supply and sanitation problems
	Injury	Traffic
Construction	Poisoning, injury	Inadequate occupational safety measures
	Communicable diseases associated with poor living conditions	Poor sanitation, poor water supply, poor food hygiene
Operation	Vector-borne diseases Excreta-related disease	Blocked drainage, domestic water storage, solid waste
	Injury	management Traffic

The main features of exposure assessment and health impact characterization in an EIA study is that exposures to the health impact causing agents and their subsequent effects must be determined for the no action alternatives (the project is not implemented) and the proposed action and its alternatives. Thus, the health effects characterized for the no action alternative provide the baseline condition against which the health effects characterized for the proposed action and its alternatives can be compared. The information obtained during the description of the project and the environment is critical to these steps. An important consideration in assessing exposures within the EIA process is that many of the methods, tools, and techniques used to predict other biophysical environmental impacts may be used to determine exposure to health impact causing agents.

Finally, health impact characterization consists of two parts. The first part combines the environmental doses estimated in the exposure assessment and the dose-response values determined in the dose-response assessment. The results, depending on the health impact being assessed, can be expressed as probabilities of the health impact occurring for non-threshold effects, and hazard indices or margins of safety indices for threshold effects. This characterization of health impacts assumes that exposure to the health impact causing agent has occurred only sporadically (e.g., an accident). Therefore, the probability of occurrence of such events also needs to be considered and/or calculated and combined with the results of the first part as necessary.

9.5.3.4 Interpreting health impacts

The activity that follows prediction of health impacts is their evaluation or interpretation. For many health impacts, appropriate standards do not exist for determining whether the predicted effects are acceptable or not. In the context of the EIA process the evaluation of health impacts can be performed by taking into consideration several factors, including regulatory criteria, institutional information that might be relevant to the health effects or health impact causing agents being considered, the repercussions of the health effects at the individual and populational levels, the evidence that the health effect occurs in humans, the level of confidence in the quantitative and qualitative information used to estimate dose-response relationships, the level of confidence in the exposure estimates, and, finally, the public perceptions related to the health effects.

9.5.3.5 Mitigation, monitoring, and reporting

Depending on the evaluation of health impacts some may be found to be objectionable; therefore, mitigation measures may be needed. The mitigation process involves two tasks: (1) identifying the appropriate mitigation measures or measures, and (2) estimating the magnitude by which the health impact will be reduced. For most projects, mitigation measures to minimize undesirable health effects fall into one or more of three categories: (a) mitigation through control of sources, (b) mitigation through control of exposure, and (c) mitigation through health service development.

Information regarding the evaluation of health impacts and mitigation measures, together with the information on other environmental impacts should then be used by decision makers to select the proposed action from the alternatives evaluated. A number of more or less complex decision-making procedures have been developed to assist at this stage in the EIA process. In terms of health impact assessment methodology, the aim of this activity is not the selection process itself, but the organization and presentation of the health impact information, integrated with other environmental impact information, in a way that is most useful to the decision makers.

The selection of the proposed action should be accompained by the design of a health monitoring programme if potentially significant health impacts are expected to result from the implementation of the action. One objective of monitoring is to check predicted impacts, thereby allowing responsible entities to validate, modify, and/or adjust the prediction techniques used. Monitoring could also be used in project management decisions. The health monitoring system should be designed in coordination with other environmental monitoring systems in order to minimize resources and avoid duplication of efforts.

The preparation of the written documentation may be the last activity to be completed, but not necessarily the last to be initiated. As a part of this health assessment methodology, it is recommended that the previous activities be documented. This information should then be integrated in the EIS in such a way that it reflects that the health impact assessment was conducted with due consideration in the overall EIA process. Thus, each of the sections of the EIS should contain succinct information pertinent to the assessment of health impacts, which are extensive material generated in connection with the health impacts assessment incorporated as appendices, and with external supporting data and literature adequately referenced.