The relationship between ambient air pollution and life expectancy - an ecological fallacy revisted.

INTRODUCTION: The results of multiple studies indicate the negative impact of exposure to air pollution on human life expectancy. Epidemiological evidence on this relation is in large proportion provided by ecological studies, what causes interpretation difficulties. Poland is a country characterized by large territorial differences in ambient air pollution and in life expectancy. This promotes analyses of the mentioned relationship based on ecological model. AIM: The aim of the study was to analyse the results of a simple ecological study concerning the relationship between life expectancy and air pollution with the focus on the difficulties in interpretation of the results. MATERIAL AND METHODS: The study used a simple ecological study approach. We used the official data on sex-specific life expectancy for year 2018 and annual average ambient air concentrations of PM2.5 in years 2010-2018 for 10 large metropolitan areas in Poland. The data was used as a marker of long-term air pollution levels in particular areas. Associations between life expectancy and air pollution levels were assessed using Spearman correlation analysis. RESULTS: The analysis concerning exposure to air pollution and life-expectancy in several Polish large agglomerations did not show statistically significant associations. CONCLUSIONS: Our ecological study did not show statistically significant associations between life expectancy and ambient air pollution levels measured by means of PM2.5 concentrations. Ecological nature of the population's exposure marker, without considering many important factors influencing length of life, may explain the negative results of the correlation analysis. This is an example of so called ecological fallacy, affecting the used model of epidemiological study.