Is a dense city a healthy city? A preliminary study on the interplay between urban density and air quality in Oran, Algeria

Abstract

The general consensus is that dense cities are more sustainable. However, high urban density or compact urban form may affect the health of city dwellers, more particularly when compactness is not associated with the provision of mass transit systems. This paper analyses the correlation between urban density indicators and air pollution in Oran (Algeria), a city that suffers a lack of public transport. It assesses the density of green space needed to reduce airborne pollutants in cities. The paper also examines the impacts of exposure to air pollution on respiratory mortality using a quantitative health impact assessment methodology. Findings show that population density and building density strongly correlates with air pollution, due to motorized transport and other human activities (e.g. industries, residential heating or lacking green space). Results indicate that for population density greater than 12100 inhabitants/ha with associated values exceeding 100 for building density and green space density, air pollution levels become higher than 40µg/m3 , exceeding the recommended limit at international level by WHO. In addition, 588 annual premature deaths (95% CI: 529-643), i.e. 0,2% of the total population of the eighteen districts and 3,7% of the total number of deaths, were directly or indirectly related to NOx concentration. This paper concludes that despite the conventional wisdom that more dense cities are more sustainable and healthier, higher density urban areas tend to be associated with poor air quality when there are no mass transit systems.

Keywords

• urban density
• air quality
• health risk
• air pollution
• mortality