Dear Colleagues,

Airborne particulate matter (PM) is a critical issue for the environment and human health. The European Environment Agency (EEA) estimated that PM_2.5 concentrations in 2018 were responsible for about 379 000 premature deaths originating from long-term exposure in Europe. The potentially adverse health effects due to PM inhalation can be related not only to particle size, but also to their physico-chemical characteristics, which vary significantly in urban, industrial and rural areas. With the introduction of smart cities concept, suitable measures to reduce people exposure to pollutants must be part of the policies for a suitable urban development. Generally urban policy makers have proposed some restrictions (for example for traffic), that were insufficient. Then, different approaches may be considered to minimize the PM exposure and health risks.

Filters are the conventional methods widely adopted for PM entrapment. However, the existing materials for air filters are generally petroleum-based materials, with high costs both from an economical and environmental point of view. Another disadvantage is the disposal of exhaust filters: the filter regeneration is generally not planned, making the material substitution the most common practice to replace exhaust filters. In addition, the disposition of used air filters can cause secondary environment pollution, mainly due to the air filter materials (generally polymers).

Actually, the most sustainable, effective and low-cost method able to reduce the concentration of PM in urban areas is represented by leaves: vegetation cover plays a key role in air quality, with the ability to trap PM. However, there are several limitations and barriers to achieve air PM trapping by urban greening only, including prevailing soil conditions, space utilization, architectural design and sub-surface infrastructure. In addition, leaves cannot survive in winter.

It is evident that new solutions must be applied to guarantee a significant PM reduction in urban spaces. This special issue aims to collect different papers or review articles about innovative materials and techniques to improve the air quality of urban environment.

Prof. Dr. Elza Bontempi
Dr. Alessandra Zanoletti
Guest Editors

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• PM pollution reduction
• sustainable materials
• porous materials
• innovative techniques
• recycle of waste
• waste minimization
• improve air quality