Every year the concern from environmental pollution increases as it affects human health. In the current paper, it is analyzed the evolution of the air quality in different cities on international level related to the reduction in mobility trend due to the emergence of the pandemic. The air pollution is studied in order to achieve healthier cities in the future and create an awareness for the citizens. The COVID-19 pandemic situation was declared during the first months of 2020 and has shown (indirectly) the effects that restrictions on human activity and road traffic have on atmospheric pollutant values. This pandemic condition derived, in most cases, in mobility restrictions in order to decrease the spread of the virus through the density of population in different places and, as a result of these restrictions, pollutant presence decreased equally. This article analyzes some of the largest cities around the world, such as Tsuen Wan district in Hong Kong (China), Los Angeles (USA), London (UK), São Paulo (Brazil), Bangalore (India), Johannesburg (South Africa), and Sydney (Australia) in order to check the different mobility restriction policies established in each location, and how those restrictions led to decrease the levels of some pollutant particles such as NO 2 in the atmosphere. This should serve as a focus of awareness of the city and political interests of how it affects human activity, and those measures should be taken to reduce pollutants.

The construction and demolition sectors are among the world’s most critical activities, generating large amounts of waste. Thus, these sectors’ waste accumulation problem is related to the environmental protection system and proper waste management. On the other hand, it is well known that proper waste disposal can increase its value. In this way, the economic potential of the trash can be raised again. Therefore, this article will examine the economic potential of construction and demolition (C & D) waste. Different waste management processes will be analyzed to better understand the topic from a financial perspective in this area underway in Spain. Therefore, data from other regions of Spain were collected. This data led to results where the most expensive rooms were Pais Vasco and the Balearic Islands, where disposal of C & D waste had the highest prices, exceeding EUR 30 per ton. Conversely, the lowest prices are found in regions such as Navarre and Andalusia, where prices per ton are EUR 8 and EUR 6, respectively. The values show a direct relationship between the treatment price and the amount of C & D waste disposed of. Therefore, this article will look at different factors influencing sustainable waste management. Such activities have a positive impact, as waste needs to be recycled and reevaluated by waste management operators. The cost of construction waste is an integral part of the budget because it represents the monetary value of the cost of collecting and recycling construction waste. Construction waste is an essential resource for economic and social development, as it contributes to job creation, education and culture, and the protection and preservation of the environment.

<abstract> <p>The construction of protected housing in Spain during the period analysed (1939–1989) reached its maximum between 1950–1980 with the construction of almost three million homes per year. The analysis of the homes built for railroad workers from this housing stock is distinct for four main reasons: it is a housing stock with a representative number of homes in relation to the total of social housing built in Spain, which is still mostly in use and covers all the typologies used in the country and which is dispersed throughout it. Thus, for the present analysis, there is a sample that is adequately representative of the whole stock of social housing constructed in Spain, this sample enables a comparative global analysis that can be extrapolated to the remaining stock. The objective of this study is to analyse the energy efficiency of homes through the thermal analysis of the envelope, as well as to acknowledge the specific constructive limitations of these homes and if possible, their rehabilitation that guarantees compliance with the required standards regarding sustainability and energy efficiency set by the Sustainable Development Goals (SDGs) established in the 2030 Agenda. This is a crucial goal to achieve, as the Spanish building stock currently consumes 30% of the total energy consumed, in addition to the socioeconomic profile and the potential for energy poverty, there is a portion of social housing with a precarious construction lacking the heating facilities, which is required due to the weather, with a significant potential for savings and the incorporation of renewable energies.</p> </abstract>