The environment poses a diverse range of health risks. Environmental burden of disease (EBD) studies try to estimate the impact of environmental stressors in terms of mortality or morbidity on a population level. Although environmental risks have been studied in Flanders, an effort to routinely quantify the environmental disease burden completely and coherently has thus far not been established. For this reason, Sciensano and Departement Zorg are partnering up in a project to map the Environmental Burden of Disease in Flanders (EBoD-FL).
The aim of the research is to inventory the burden of disease attributable to all relevant environmental stressors according to a coherent framework. To tackle this objective, the disease burden attributable to environmental stressors is estimated using comparative risk assessment (CRA). As this method determines the attributable burden proportionally, figures for the total disease burden are required as a baseline to obtain absolute estimates. In EBoD-FL, the EBD is quantified as disability-adjusted life years (DALYs), a summary measure that combines both mortality and morbidity.
In EBoD-FL, a novel approach is developed where the EBD is calculated locally at the level of the statistical sector. This approach adds geographic detail to the EBD estimates, and allows to mutually compare small areas and local populations. Additionally, the local results can be aggregated to wider areas and larger populations, which allows to extract estimates for any part of the Flemish Region in a flexible manner. As collecting the necessary data on this fine-scale level poses a challenge, a parallel track of calculations was set up, where the EBD is determined ‘globally’ on the level of Flanders. Data on this aggregated level (Flanders) are relatively easy to obtain, which allows to complete the steps in the analysis more swiftly.
Given the extensive list of potential risk factor-health outcome pairs, a set of priorities was defined in terms of environmental stressors and health outcomes. The risk factors that were prioritised are those related to air quality, environmental noise and extreme temperature. In terms of outcomes, priority was given to all-cause mortality, respiratory diseases and cardiovascular diseases. This report outlines the CRA methodology in general, and the application on the risk-outcome pairs that have been given priority. The basic steps of CRA are:
- Selection of risk factors: Which risk factors are included in the study and how is exposure quantified as a metric?
- Exposure assessment: how to measure or model exposure to the risk factors in the population?
- Identification of risk-outcome pairs: which health outcomes are caused by the risk factors?
- Quantification of the risk-outcome relation: what is the risk of developing the outcome in function of exposure?
- Calculation of the population attributable fraction: what is the proportion of the disease burden attributed to one or multiple risk factors?
The purpose of this report is to outline the general methodology used to tackle the objective of EBoD-FL and to apply the CRA methodology to the stressors that are prioritized. Additionally, possibilities for the application of the results for evidence-based policy are explored, as well as some challenges and limitations.
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