EPIDEMIOLOGY &SOCIETYHow Much Disease Burden can be Preventedby Environmental Interventions?Annette Pru¨ss-U¨stu¨n and Carlos Corvala´nAbstract: There is very little systematically collected evidence onthe overall contribution of environmental risk factors to the globalburden of disease. The World Health Organization (WHO) recentlycompleted a comprehensive, systematic, and transparent estimate of thedisease burden attributable to the environment highlighting the fullpotential for environmental interventions to improve human health.This report is the result of a systematic literature review onenvironmental risks completed by a survey of expert opinion usinga variant of the Delphi method. More than 100 experts providedquantitative estimates on the fractions of 85 diseases attributable tothe environment. They were asked to consider only the contributionsof the “reasonably modifiable environment”—that is, the part ofenvironment that can plausibly be changed by existing interventions.The report estimates that 24% of the global burden of diseasewas due to environmental risk factors. Environmental factorswere judged to play a role in 85 of the 102 diseases taken intoaccount. Major diseases were, for example, diarrheal diseaseswith fractions attributable to the environment of 94%, lowerrespiratory infections with 41%, malaria with 42%, and uninten-tional injuries with 42%. The evidence shows that a large pro-portion of this “environmental disease burden” could be avertedby existing cost-effective interventions such as clean water, cleanair, and basic safety measures. In children, 34% of the diseaseburden is attributable to the environment, and much of thisburden is in developing countries.(Epidemiology 2007;18: 167–178)Environmental health action can improve population healthin a sustainable manner and improve equity. Such actioncan also make a major contribution toward achieving 6 of the8 Millennium Development Goals and thus may be a prereq-uisite for their success.The role of environmental management in improvinghealth has been neglected in recent years. This neglect ispartly due to competition for resources and policymakers’attention from more immediately obvious health threats aris-ing from, for example, the HIV/AIDS pandemic. It alsoresults from the perceptions that environmental risk factorshave only a relatively small impact on the global burden ofdisease and that investments in environmental managementhave low cost-effectiveness in comparison with other healthinterventions.In reality, there is very little evidence to support theseperceptions. Although the role of environmental interventions indisease prevention has been assessed for selected risks anddiseases, until recently, there has been no systematic and con-sistent assessment of the global burden of disease resulting fromenvironmental risk factors or of the effectiveness or cost-effec-tiveness of these interventions.The WHO has now completed a study designed to esti-mate the disease burden attributable to the environment toaddress the full potential of environmental interventions toimprove human health.1This study was based on a 6-yearprocess to quantify how much disease can be attributed tovarious environmental risks. In this commentary, we describethe methods used to arrive at these estimates, and we sum-marize the key findings. We present a systematic review ofthe literature for quantitative assessments of populationhealth impacts from environmental risks with informationgaps completed by quantitative estimates from experts in therelevant fields. We provide attributable fractions and globaldisease burden due to the environment for every considereddisease and injury category, and we outline the areas whereenvironmental interventions are likely to bring the greatesthealth gains. Full details of this analysis are provided in thecomprehensive publication.1Previous estimates of the global burden of disease dueto the environment were 23%2and 25% to 33%3; for coun-tries of the Organisation for Economic Co-operation andDevelopment (OECD), the estimate was 2% to 5%.4Further-more, the WHO recently coordinated the Comparative RiskAssessment, which quantified the health impacts of 26 majorrisks, 6 of which were environmental, using a comparativeframework.5,6We based our work on these previous studiesand further improved or completed them by: 1) enlarging theFrom the Department of Public Health and the Environment, World HealthOrganization, Geneva, Switzerland.The views expressed in this article are those of the authors and do notnecessarily reflect the position of the World Health Organization.Editors’ note: Related articles appear on pages 162 and 179.Correspondence: Annette Pru¨ss-U¨stu¨n, Department of Public Health and theEnvironment, World Health Organization, 20, Avenue Appia, CH-1211Geneva, Switzerland. E-mail: [email protected] © 2006 by Lippincott Williams & WilkinsISSN: 1044-3983/07/1801-0167DOI: 10.1097/01.ede.0000239647.26389.80Epidemiology • Volume 18, Number 1, January 2007 167scope to include most of the risks contained in the environ-ment (eg, 8 other major risk factors in addition to the 6explored in the Comparative Risk Assessment as well as thework environment, which had not been included in the OECDstudy); 2) systematically reviewing 102 diseases and injuriesas to their environmental causes (eg, the Comparative RiskAssessment reviewed 42 diseases for selected environmentalcauses but covered the majority of environmental causes ofonly 2 diseases); 3) consulting experts to complete gaps in theevidence to obtain a more comprehensive estimate of thepotential of healthy environments to prevent disease; and 4)limiting the environment to only the “reasonably modifiableenvironment” to improve the policy relevance of results. Inthis review, more than 100 experts throughout the world wereconsulted to provide attributable fractions of 83 diseases and2 risk factors (physical inactivity and malnutrition), providinga substantially greater coverage than achieved in previoussystematic reviews such as the Comparative Risk Assess-ment. The experts are all listed in the full report1and theircontribution is gratefully acknowledged.WHAT IS THE ENVIRONMENT? WHATCAN BE PREVENTED?To be relevant to policy, the definition of environmentused in this study was “the physical, chemical and biologicenvironment to the human host and related behavior, but onlythose parts that could reasonably be
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