Urbanization trends and environmental concerns are interconnected due to the increased demand of natural resources, waste production and greenhouse gas emissions. One of the most important anthropogenic factors affecting ecosystems and sustainability is the rapid growth of cities in both size and complexity. According to United Nations as at mid-2017, the global population was an estimated 7.6 billion people, and it is expected to reach 9.8 billion (2050). As the world urbanizes, the role of cities in defining sustainability outcomes increases in importance. Even though cities expansion contributes to economic prosperity and social growth, at the same time, it poses severe challenges both to the environment and social system. The changing from “unsustainable cities” to “sustainable, green and smart cities”, has become a major topic in research community and policy making for endorsing urban sustainability. As a result, the United Nation Sustainable Development Goals were developed as an ambitious blueprint for achieving peace and prosperity while also protecting the environment. Especially SDG 11 is dealing with making cities inclusive, safe, resilient and sustainable. Moreover, Circular Economy is receiving increasing attention globally as a way to overcome the current production and consumption model based on continuous growth and increasing resources input, with aim to increase the efficiency of resource use in order to achieve balance and harmony between economy, environment and society. The objective of this paper was to identified the major challenges occurred due to the rapid urbanization in a coastal area giving emphasis to Particulate Matters Emissions PM2.5, and how the use of the PM2.5 emission index could be used as an indicator for determining the urban metabolism of an island area taking into account that the increase in the concentration of PM in an area is directly related to the increase of anthropogenic activities resulting from population growth and consequently the increase in flows of materials and services and at the same time the increase in the production of solid and liquid waste and gaseous emissions. The higher the index, the greater the degree of metabolism of an area and the impact on air quality.
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