Assessment of air pollution impact on chronic disease:
new study published from WHO EMAPEC project

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Health impacts of air pollution

To plan and implement effective actions to reduce air pollution, we need to know how many people suffer from exposure to air pollution in a given population. However, assessment of air pollution often omits important morbidity outcomes, thus underestimating the full burden of air pollution and the related economic impacts. This new study aims to address this gap by estimating the number of affected individuals using Health Risk Assessment methods (HRA). These methods are based on evidence from epidemiological studies that provide a functional link between an exposure level (i.e., the concentration of an air pollutant) and the risk of a certain health outcome, known as the concentration-response function (CRF).

The best-established functions link the concentration of particulate matter (PM_2.5) or nitrogen dioxide (NO₂) with mortality. Consequently, the estimate of over four million deaths per year attributed to ambient air pollution globally is the result of the analysis using these functions. However, studies linking morbidity (i.e., disease occurrence) with exposure to air pollution are less common. Additionally, estimates of the number of disease cases attributed to air pollution are rarely used to support policy discussions. Meanwhile, economic and societal morbidity costs are high and create significant burden to national budgets and people wellbeing.

Assessment of air pollution impact on morbidity

Estimating the morbidity from air pollution and its economic costs (EMAPEC)  is the named objective of the project coordinated by the World Health Organization.

A group of experts from different institutions reviewed the scientific evidence on CRFs by analysing the available systematic reviews for various morbidity endpoints. It identified the functions linking asthma in children, chronic obstructive pulmonary disease, ischemic heart disease events, stroke, hypertension, diabetes (type 2), dementia, autism spectrum disorder, lung cancer with long-term exposure to PM_2.5, and asthma in children, asthma in adults, acute lower respiratory infection in children with long-term exposure to NO₂.

The article “Choices of morbidity outcomes and concentration–response functions for health risk assessment of long-term exposure to air pollution,” published in the Environmental Epidemiology, summarizes the project´s results and suggests reliable concentration–response functions to be applied in HRA of long-term exposure to air pollution. The project used a comprehensive approach to selecting CRFs based on causality considerations, reliability appraisal of the systematic reviews and meta-analyses providing the CRFs, and confidence in the epidemiological evidence as the sources of the CRFs.

Importantly, the article also addresses the conditions for the applicability of the selected risk functions in the HRA. It defines the population groups of concern, range of exposure, and its changes under considered scenarios, which could be the subject of reliable assessment of air pollution impact on chronic disease. A report from the EMAPEC project (in preparation) will include the results presented in the article and present their application in several case studies. The EMAPEC report will also contain an economic assessment of the impacts of air pollution on morbidity.

Estimating the related economic costs

Climate and Clean Air Coalition (CCAC) funded the EMAPEC project with support from the Norwegian Agency for Development Cooperation (NORAD) and the Spanish Agency for International Cooperation (AECID). The Environment Research Group at Imperial College London, Sante Publique France, and the Lazio Region Health Service in Italy provided in-kind contributions.

EMAPEC aims to establish a methodology to estimate economic costs of selected morbidity outcomes of exposure to air pollution within a population.  A pilot test for one or two case studies will explore challenges that may result from a lack of data, and address various geographical scales (regional, national, and global) and different contexts for assessment of air pollution impact on chronic disease.

Learn more about Estimating the morbidity from air pollution and its economic costs (EMAPEC).