Nitrogen dioxide (NO₂) remains one of the most relevant traffic-related air pollutants in urban environments, despite decades of regulatory efforts and advances in vehicle emission control technologies. This review synthesizes current knowledge on ambient NO₂ concentrations associated with road transport, identifies key determinants of spatial and temporal variability, and evaluates the effectiveness of mitigation approaches under increasingly stringent air quality standards. The study is based on a comprehensive review of peer-reviewed literature reporting NO₂ measurements in urban, traffic, and background environments worldwide, complemented by an assessment of regulatory frameworks and mitigation strategies. The evidence confirms that road transport is the dominant contributor to elevated NO₂ concentrations, particularly at traffic sites, with traffic intensity, fleet composition, driving behavior, cold-start emissions, and street geometry emerging as primary controlling factors. Meteorological conditions influence dispersion but generally play a secondary role compared with emission-related drivers. Urban infrastructure, especially street canyons and tunnels, amplifies near-road NO₂ levels and population exposure. Mitigation measures such as Low Emission Zones, vehicle fleet modernization, and infrastructural interventions can reduce NO₂ concentrations, but their effectiveness is moderate and highly context-dependent. Sustained compliance with EU limit values and World Health Organization guideline levels requires integrated, multi-scale mitigation strategies.

The goal of the study was to determine the concentrations of submicron particulate matter (PM₁) and of the mercury contained in it (Hg_p) in the air in two teaching rooms in two Polish cities, Gliwice and Warsaw. The levels of atmospheric particulate matter (PM) differ greatly between these two cities. The relations between the indoor (I) and outdoor (O) 24-h concentrations for each PM₁ and Hg_p were determined and, based on the conclusions, an attempt was made to identify the main sources of the indoor Hg_p in both cities. During the whole measuring period (April–June 2015), in both Warsaw and Gliwice, the 24-h outdoor PM₁ concentrations were slightly higher than the indoor ones (outdoor and indoor averages were equal to 19.3 µg m⁻³ and 14.5 µg·m⁻³, respectively, in Gliwice and to 13.2 µg·m⁻³ and 9.5 µg·m⁻³ in Warsaw). In Gliwice, the indoor concentrations of Hg_p (2.4 pg·m⁻³ to 27.7 pg·m⁻³) were much higher than the outdoor ones (1.1 pg·m⁻³ to 6.1 pg·m⁻³); in Warsaw the average concentrations of Hg_p were equal to 1.4 pg m⁻³ indoors and outdoors. The 24-h concentrations of Hg_p and the 24-h I/O ratios for Hg_p varied more intensely in Gliwice than in Warsaw throughout the whole measuring period. In Warsaw, the teaching room Hg_p came mainly from the infiltration of atmospheric (outdoor) Hg_p. In Gliwice, a part of the indoor Hg_p infiltrated into the teaching room with the outdoor PM₁ that most probably was then enriched with gaseous indoor Hg, what resulted in the relatively high indoor Hg_p concentrations.

(1) Background: On the Internet, we can find the guidelines for homemade air purifiers. One of the solutions includes the use of a low-cost ozone generator to decrease the level of odors and biological contaminants. However, the authors do not notify about hazardous effects of ozone generation on human health; (2) Methods: We elaborated our test results on the bacterial and fungal aerosol reduction by the use of two technical solutions of homemade air purifiers. First, including a mesh filter and ozone generator, second including an ozone generator, mesh filter, and carbon filter. (3) Conclusions: After 20 min of ozone generation, the concentration of bacteria decreased by 78% and 48% without and with a carbon filter, while fungi concentration was reduced in the lower range 63% and 40%, respectively. Based on our test results, we proposed a precise periodical operation of homemade air purifier to maintain the permissible level of ozone for the occupants.

One of the greatest challenges humankind currently faces is global warming, mainly caused by greenhouse gas emissions. Here we have attempted to show how thermal conversion products, specifically from the pyrolysis of biomass wastes such as sewage sludge, can be used effectively and equivalently to sequester CO₂ in brownfield and degraded areas. Scenarios were devised that showed the significant potential for CO₂ sequestration in the form of biochar from sewage sludge deposited on degraded and brownfield areas. With the current amount of sludge production, such sludge could even be used in its entirety as a raw material in pyrolysis processes, where, in addition to the biochar, the heat necessary for drying the sludge could be generated and high-energy gas and liquid fractions could be obtained, which could be used to produce alternative fuels. It is therefore important to consider both the potential for CO₂ sequestration on degraded and brownfield sites and the potential for sludge disposal in Europe as viable options for reducing greenhouse gas emissions and promoting sustainable waste management practices.

(1) Background: Since exposure to airborne bacteria and fungi may be especially hazardous in hospitals and outpatient clinics, it is essential to sterilize the air in such rooms. The purpose of this study was to estimate the decrease in the concentration of airborne bacteria and fungi in the selected hospital and clinic rooms due to the work of the electron wind generator (EWG). (2) Methods: EWG is an air movement and air purification device using a sophisticated combination of electrode topology and specially designed high-voltage power supply. (3) Results: The concentration of both bacteria and fungi in the small patient’s room dropped to approximately 25% of the initial (background) concentration. In the larger patient’s room, the concentration dropped to 50% and 80% of the background concentration for bacteria and fungi, respectively. (4) Conclusions: The obtained data show that the studied sterilization process can be described by the exponential function of time. Moreover, the application of an activated carbon filter into EWG significantly decreases the concentration of ozone in the sterilized room. Sterilization by EWG significantly changes the characteristic of species and genera of airborne bacteria and shifts the main peak of the size distribution of airborne bacteria into the coarser bio-particles.

One of the basic documents of the Environmental Impact Assessment (EIA) procedure is the Environmental Impact Report. It contains information obtained during the investor’s assessment of any impact on the environment that may be caused by the object – also from the side of construction works at the investment stage. The authors, on the basis of nitrogen dioxide concentration data obtained from continuous, multi month measurements carried out with the use of the OPSIS device over the diametrial route DTŚ construction site in Gliwice, have evaluated the NO ₂ emission impact on the atmospheric air at the construction phase. The measurements made by the authors enabled in verifying the correctness of the assessments and comments regarding the impact of construction works conducted on the route DTŚ on the atmospheric air in the construction phase, contained in the Environmental Impact Report.