Indoor air quality is a significant aspect of public health, yet it remains less studied than outdoor air pollution. Understudied indoor pollutants include volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs). This review focuses on these two groups of compounds known for their health effects, including respiratory issues, neurological disorders, and carcinogenicity. We systematically compiled and analyzed data from studies reporting measured concentrations of VOCs and PAHs in European indoor environments—homes, schools, and offices—published in the past two decades. Concentration levels vary substantially across studies, influenced by regional differences, climate, building type, ventilation systems, and indoor activities. Identified sources include tobacco smoke, cooking, heating (e.g., biomass burning), and off‐gassing from construction and furnishing materials. Our analysis reveals clear geographic patterns: lower concentrations of VOCs and PAHs are consistently reported in Northern and Western European countries, likely due to stricter air quality regulations, cleaner outdoor air, greater use of electric heating, and more advanced ventilation systems. Conversely, higher concentrations are more commonly observed in Southern and Eastern Europe, where biomass heating and poorer ventilation remain more prevalent. Seasonal variation also has a significant role, with higher indoor levels typically measured during colder months due to increased heating and reduced air exchange. This highlights the need for improved indoor air quality management practices and regulatory standards to minimize the health risks associated with VOCs and PAHs. This review of 46 scientific publications is aimed at informing future studies and guiding future field measurements and risk assessments in epidemiological studies.

Polycyclic aromatic hydrocarbons (PAH) are key components of particulate matter (PM) in terms of the toxicological risk of polluted air. Although commonly monitored in ambient air, PAHs are also present in indoor air, making the measurement of indoor PAH content essential for understanding the health risks associated with indoor environments. This study presents findings from measurements conducted across 37 households where children resided, using 7-day sampling campaigns to collect PM₁. The health risk assessment methods are detailed herein, along with a source apportionment analysis to explore the associations with potential sources and differences from ambient air concentrations. Additionally, the incremental lifetime cancer risk (ILCR) was calculated to assess long-term health risks associated with exposure to indoor PAHs. The results showed consistently higher PAH concentrations in outdoor environments (from 0.079 ng m⁻³ for dibenzo(a,h)anthracene to 1.638 ng m⁻³ for benzo(b)fluoranthene) compared to indoor environments (from 0.029 ng m⁻³ for dibenzo(a,h)anthracene to 0.772 ng m⁻³ for indeno(1,2,3-cd)pyrene), suggesting significant transfer of PAHs from outdoor to indoor air. The source apportionment analysis indicated that traffic emissions, fossil fuel combustion, and residential heating were the predominant sources of PAHs in both environments, with the concentration of indoor PAHs largely influenced by gasoline and liquid fossil fuel combustion. The diagnostic ratios supported these findings, with coal and biomass as additional sources impacting outdoor PAH levels. The ILCR analysis revealed that the exposure levels for both children (indoors at 1.78 × 10⁻⁵, outdoors at 1.92 × 10⁻⁶) and adults (indoors at 1.15 × 10⁻⁵, outdoors at 1.24 × 10⁻⁶) remained below the U.S. EPA’s risk threshold, suggesting limited carcinogenic risk under typical household conditions in this study. These findings emphasize the complexity of PAH distribution between indoor and outdoor environments, illustrating how urban outdoor pollution sources contribute to indoor air quality and highlighting the relevance of effective air quality management strategies.

Understanding how traffic contributes to air pollution, especially in urban areas, is essential for designing effective strategies to reduce air pollution emissions. This study examines the hourly association between traffic volume and concentrations of two air pollution indicators (NO₂ and PM₁₀) using high-resolution data from two monitoring stations in Helsinki. A Prophet time series model was applied to forecast hourly traffic trends for 2024, which were then compared to yearly average NO₂ and PM₁₀ concentrations. Polynomial regression and cross-correlation analyses were used to capture temporal patterns and assess the strength and timing of the relationship. The results show a strong alignment between traffic and NO₂ and PM₁₀ concentrations, particularly at the traffic-heavy measuring site (Mäkelänkatu supersite), with minimal time lag observed. Root mean square error (RMSE) and polynomial fit comparisons confirmed the predictive value of traffic trends in estimating the behavior of NO₂ and PM₁₀ concentrations. These findings support the use of traffic-based proxy models as practical tools for real-time air pollution assessment and for informing targeted urban air quality interventions.

Understanding how atmospheric pollutants interact with soil pollution is essential for assessing long-term environmental and human health risks. This study compares concentrations of polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) in PM₁₀ and surface soil near air quality monitoring stations in Zagreb, Croatia. While previous work identified primary emission sources affecting PM₁₀ composition in the area, this study extends the analysis to investigate potential pollutant transfer and accumulation in soils. Multivariate statistical tools, including correlation analysis and principal component analysis (PCA), were employed to gain a deeper understanding of the sources and behavior of pollutants. Results reveal significant correlations between air and soil concentrations for several PTEs and PAHs, particularly when air pollutant data are averaged over extended periods (up to 6 months), indicating cumulative deposition effects. Σ11PAH concentrations in soils ranged from 1.2 to 524 µg/g, while mean BaP in PM₁₀ was 2.2 ng/m³ at traffic-affected stations. Strong positive air–soil correlations were found for Pb and Cu, whereas PAH associations strengthened at longer averaging windows (3–6 months), especially at 10 cm depth. Seasonal variations were observed, with stronger associations in autumn, reflecting intensified emissions and atmospheric conditions that facilitate pollutant transfer. PCA identified similar pollutant groupings in both air and soil matrices, suggesting familiar sources such as traffic emissions, industrial activities, and residential heating. The integrated PCA approach, which jointly analyzed air and soil pollutants, showed coherent behaviour for heavier PAHs and several PTEs (e.g., Pb, Cu), as well as divergence in more volatile or mobile species (e.g., Flu, Zn). Spatial differences among monitoring sites show localized influences on pollutant accumulation. Furthermore, this work demonstrates the value of coordinated air–soil monitoring in urban environments and provides an understanding of pollutant distributions across different components of the environment.