Perspectives on health impact assessment.

Abstract

One stream of health impact assessment(HIA)canbeseenasanaturaldevelopmentof environmental impact assessment,treating human communities as an impor-tantpartoftheecosystemstobeprotected.This approach was first applied to con-struction projects in developing countries(1) but was soon influencing other coun-tries (2–4). Another stream of HIA hasitsoriginsinthenotionsofdeterminantsofhealth (5) and healthy public policy (6).One of its earliest applications was inCanada, but it has also been influential inEurope (7–9). Examples of both streamswill be found in this theme issue. Twobroad disciplinary approaches to HIAcan also be specified, one based onepidemiology and toxicology, and theother on social sciences. In addition,it is possible to distinguish between HIAapplied to projects and HIA applied tobroadpolicyandstrategymatters.Papersinthisissuedemonstratealltheseapproaches.Until there is a shared understandingof terms, no debate is possible. HIA,like other fashionable expressions, hasbeen used to name a wide variety ofactivities and is in danger of becomingso all-embracing as to be meaningless.Variousdefinitionshavebeenoffered,butthe two essential characteristics of HIAare that it seeks to predict the futureconsequences for health of possibledecisions; and that it seeks to informdecision-making.If one accepts these as the twonecessary and sufficient characteristicsof HIA, various conclusions follow. Firstall HIA is prospective, and the terms‘‘retrospective HIA’’ and ‘‘concurrentHIA’’ (used in some of the papers in thisissue of the Bulletin) should be droppedand replaced with others such as ‘‘evalua-tion’’, ‘‘surveillance’’ and ‘‘monitoring’’.Second, many activities , though theydo not call themselves HIA, are. Prospec-tive comparative risk assessment (10)isone of these. Third, many other activities,though they call themselves HIA (includ-ing the paper in this issue by Leonard(see pp. 427–433), are not. Activities suchas needs assessment, community devel-opment, public health surveillance andadvocacy do not have these two definingcharacteristics and so are not HIA. Indenying them thetitle of HIA, we are not,of course, denying that they are valuablecontributions to public health.Health impact assessment relies onunderstanding causal links so as to predictthe consequences of proposed actions.Epidemiology and toxicology produceevidence for some causal links, butcurrently they are only able to consider avery limited set of causative agents andan even more limited set of outcomes.Sociology and psychology provide othermeans of predicting how humans andhuman societies will react to changingcircumstances. HIA does not offercertainty in its predictions or seek toremove the need for judgement indecision-making. It can do no more thanreduce the uncertainties and inform thejudgements that decision-makers have tomake.Anyattempttoreducealloutcomesto a single metric so that options can becompared by simply summing theirvarious outcomes is probably over-ambi-tious and certainly makes it impossibleto include some important determinants.Emphasis on the relation betweenimpact assessment and decision-makingis relatively new. Early models of HIAshowed a linear process with a directassessment directly linked to decision-making (7), but the real world is far morecomplex.Anassessmentwillnotinfluencethe decision-makers unless it is designedto meet their requirements. Far too manyhealth impact assessments have not beencommunicated to the decision-makers,or failed to be policy-relevant, or arrivedtoo late to help.Health impact assessments are mostlikely to inform decision-making if thedecision-makers ‘‘own’’ the assessmentand are closely involved in all the stagesof the HIA, from scoping (defining all theelements involved) to report. One mightlogically conclude from this that decision-makers should make their own impactassessments.Whilethissolutionhasmuchtorecommend it,itisdifficult toreconcilewith the principle of openness, andpresents the risk that matters outside thenarrow policy agenda will be neglected.The problems described in the paperby Jobin (see pp. 420–426) show whyentrusting HIA to policy-makers could bedangerous.The need policy-makers have forimpartialadvicemaynotfitwiththevaluesof public health. The role of an assessor,who has to consider the advantages anddisadvantages of all options, is differentfrom that of an advocate, who makesthe case for the option favoured. Publichealth practitioners value health, equityand participation, and may find it difficultto switch from arguing for these tomaking an impartial assessment.HIA has come a long way in the past10 years, but if it is to go further it hasto concentrate on its two key tasksof predicting the future and assistingdecision-makers.