Pollutants, Volume 5, Issue 2 (June 2025) – 8 articles

In this paper, we analyse the effectiveness of microbubble technology in inactivating/reducing gram-negative, gram-positive, and radiation-resistant bacteria, including Escherichia coli, Bacillus subtilis, and Deinococcus radiodurans, respectively, in model water. Key water quality parameters such as dissolved oxygen, conductivity, pH, and total dissolved solids are recorded and presented to demonstrate their range in the current investigation. The study results indicate a reduction of 95% in E. coli, 100% in D. radiodurans, and 45% in B. subtilis following microbubble treatment. These findings suggest that ambient air microbubbles, generated using a low-cost, reagent-free, and eco-friendly venturi-type microbubble generator, represent a promising technique for reducing bacterial loads in water. Full article

Active and abandoned mining sites are significant sources of heavy metals and metalloid pollution, leading to serious environmental issues. This study assessed the environmental risks posed by potentially toxic elements (PTEs), specifically arsenic (As) and antimony (Sb), in the Technosols (mining residues) of the former Pejão coal mine complex in Northern Portugal, a site impacted by forest wildfires in October 2017 that triggered underground combustion within the waste heaps. Our methodology involved determining the “pseudo-total” concentrations of As and Sb in the collected heap samples using microwave digestion with aqua regia (ISO 12914), followed by analysis using hydride generation-atomic absorption spectroscopy (HG-AAS). The concentrations of As an Sb ranging from 31.0 to 68.6 mg kg⁻¹ and 4.8 to 8.3 mg kg⁻¹, respectively, were found to be above the European background values reported in project FOREGS (11.6 mg kg⁻¹ for As and 1.04 mg kg⁻¹ for Sb) and Portuguese Environment Agency (APA) reference values for agricultural soils (11 mg kg⁻¹ for As and 7.5 mg kg⁻¹ for Sb), indicating significant enrichment of these PTEs. Based on average I_geo values, As contamination overall was classified as “unpolluted to moderately polluted” while Sb contamination was classified as “moderately polluted” in the waste pile samples and “unpolluted to moderately polluted” in the downhill soil samples. However, total PTE content alone is insufficient for a comprehensive environmental risk assessment. Therefore, further studies on As and Sb fractionation and speciation were conducted using the Shiowatana sequential extraction procedure (SEP). The results showed that As and Sb levels in the more mobile fractions were not significant. This suggests that the enrichment in the burned (BCW) and unburned (UCW) coal waste areas of the mine is likely due to the stockpiling of lithic fragments, primarily coals hosting arsenian pyrites and stibnite which largely traps these elements within its crystalline structure. The observed enrichment in downhill soils (DS) is attributed to mechanical weathering, rock fragment erosion, and transport processes. Given the strong association of these elements with solid phases, the risk of leaching into surface waters and aquifers is considered low. This work underscores the importance of a holistic approach to environmental risk assessment at former mining sites, contributing to the development of sustainable remediation strategies for long-term environmental protection. Full article

The threats posed by Persistent Organic Pollutants (POPs) impact food safety and, by implication, food security in the polar regions. POPs tend to persist in the environment and the fatty tissues of animals, thereby constituting long-term contamination. Due to the cold climate and geography of these polar regions, they create a sink for these pollutants, which travel from their source of production and accumulate in food chains, resulting in health risks to the ecosystem, animals, and humans of the Arctic and Antarctica. In this paper, we draw attention to the threats posed by POPs and how they can lead to food insecurity, negatively affecting health due to unsafe traditional foods. A narrative synthesis methodology was employed, systematically analyzing historical data, activities, and research trends on POP contamination in polar ecosystems. We also highlight resilience promoted by Arctic governance, with a focus on how the issues of POPs became an international matter from the 1970s, with three United Nations (UN) conventions: the UN-Environment Stockholm Convention on Persistent Organic Pollutants, the UN Minamata Convention on mercury, and the UN-ECE Convention on Long-range Transboundary Air Pollution. These conventions led to the start of several monitoring activities in the polar regions, transforming the POPs into a global topic. We also consider the intertwined effect of climate change on POPs. Additionally, the human rights paradigm in relation to food security and sovereignty for polar communities is explored. Strengthening the resilience of communities in the polar regions requires recognition of these nutritious traditional foods as an aspect of cultural identity that must be safe and easily accessible. We focus on developments, improvements, the role of international cooperation, and frameworks to assist in research and regulations. Furthermore, establishing systems that engage local communities to consistently monitor POPs regularly will lead to a better understanding of these threats. Ultimately, this narrative provides a look into the past and current research of POPs and their monitoring in the polar regions. Full article

The use of ultraviolet (UV) for water disinfection is known for its chemical-free process and with no harmful disinfection by-products. Yet, the disinfection process remains time-consuming, and many studies are limited to disinfection of one or two microbial species. Direct photolytic and glass-embedded TiO₂ photocatalytic disinfection of four different bacterial species (Staphylococcus aureus, Salmonella senftenberg, Bacillus subtilis, and Escherichia coli) were assessed using UV-LED radiation with wavelengths of 365 nm. The optimization of the UV disinfection under different masses of the TiO₂ photocatalyst was evaluated. Additionally, the order of disinfection of the different bacteria species was assessed. The disinfection effects were measured based on the potential to reduce the number of bacteria species, calculated in colony-forming units/mL and log reduction units. The disinfection of Staphylococcus aureus was enhanced from 1.46 log reduction units in the UV-alone treatment to a high of 5.65 log reduction units in the UV + 0.08 g TiO₂ treatment. Regarding Salmonella senftenberg, disinfection was enhanced from 1.26 log reduction units to 3.85 log reduction units in UV-alone experimental treatments and UV + 0.04 g TiO₂, respectively. Similarly, an increase in Bacillus subtilis reduction was achieved from a low of 0.69 log reduction units to a high of 2.98 log reduction units in UV-alone treatments and UV + 0.08 g TiO₂, respectively. The disinfection of Escherichia coli was enhanced from 2.49 log reduction units (UV-alone treatment) to a high of 6.35 log reduction units (UV + 0.02 g TiO₂). The findings provide key implications and new insights into the studied bacteria species and the future application of porous glass-embedded TiO₂ photocatalysts to enhance bacteria disinfection using UV light for improved water. Full article

Chronic kidney disease (CKD) is a noteworthy global health issue affecting 10% of the world’s populace. It is increasingly linked to environmental exposures; however, the interplay of toxic metals, per- and polyfluoroalkyl substances (PFAS), and essential elements has not been fully elucidated. This cross-sectional study analyzed 5800 out of the 9245 participants from the 2017–2018 NHANES dataset to evaluate the combined effect of PFAS, essential elements, and toxic metals on CKD using logistic regression and advanced environmental mixture models, namely, Bayesian Kernel Machine Regression (BKMR), quantile g-computation (qgcomp), and Weighted Quantile Sum (WQS) regression. Our results showed cadmium (Cd) emerging as a significant contributor to CKD (OR = 2.16, p = 0.023) from the logistic regression analysis. Mercury (Hg) demonstrated the highest contribution in mixtures (posterior inclusion probability = 0.908) from our BKMR analysis, with a non-linear U-shaped dose–response relationship. Essential elements like selenium (Se) and manganese (Mn) exhibited protective correlations but complex non-linear interactions, moderating toxic metal effects from our qgcomp and WQS regression. Notably, antagonistic interactions between essential elements and some pollutants reduced the overall mixture impact on CKD, showing an overall decreasing joint effect of the combined PFAS, toxic metals, and essential elements on CKD, from the 25th to the 75th quantile. This study highlights the role of environmental co-exposures in CKD risk and highlights the need for advanced statistical and machine learning approaches in studying complex environmental mixture interactions on human health. Full article

To investigate the place-based association between BCM and air pollution in middle-aged (45–64) and older-aged women (65+) in California at the zip code level, secondary data were collected from the California Department of Public Health (CDPH) Data and Vital Statistics, CalEnviroScreen 4.0, and the American Community Survey (ACS) from the Census. Multiple linear regression was used to test the significance between air pollution and age-standardized BCM rates. The results indicate a significant association between PM_2.5 and age-standardized BCM rates for both the middle-aged and older-aged groups (β = 3.73, 95% CI [2.89, 4.58]; β = 5.33, 95% CI [2.75, 8.32], respectively). Furthermore, we found evidence of effect modification by the concentration of Hispanic women (β = −6.73, 95% CI [−9.37, −4.08]. This study provides evidence of a significant spatial association between PM_2.5 and BCM rates, which has policy implications for stricter air quality regulations and urban planning policies. Further research is needed to establish causality and the mechanism of action at the population level. Full article

Perfluoroalkyl substances (PFAS), also known as “forever chemicals”, are a class of highly stable chemical compounds that slowly contaminate waterbodies and soil. The widespread presence of PFAS is associated with adverse human health effects and is a major environmental concern. The conventional, highly sensitive methods used for PFAS detection are LC-MS/MS and solid phase extraction, but they are very complex and expensive. Therefore, there is an urgent need for sensitive, low-cost, and fast methods for the detection and removal of PFAS compounds from water and soil resources. The advancement of nanotechnology has significantly impacted advanced disease diagnosis and treatment in the last few decades. Currently, these engineered nanomaterials (ENMs) have been exploited for the development of advanced nano-enabled techniques for the detection and removal of environmental pollutants. Nano-enabled techniques also offer improved performance over conventional methods. In this review, the details of the detection and removal of PFAS, as well as their optimization and limitations, and future perspectives are discussed. We focused on the implementation of nanomaterials such as nanoparticles, nanotubes, nanorods, and nano*filtration membranes for efficient PFAS detection and removal. We also included the recent literature and global guidelines for PFAS use and the effect of PFAS exposure on human health. Full article

Exposure to contaminated soils can adversely affect health and the well-being of both humans and animals. Environmental stressors can influence the mobility and toxicity of contaminants, altering their potential impacts. This study aimed to assess the impact on the behavior of offspring from rats exposed during the gestation and lactation period to contaminated and acidified soils. Female Wistar rats were gavaged daily for 42 days with soil leachate from an industrial region known to be contaminated with metals and metalloids, using solvents with different pH values (6.0, 5.2, and 3.6). The offspring were evaluated in behavioral tests including Open Field, Elevated Plus Maze, and Inhibitory Avoidance. Our findings revealed significant statistical differences in all three tests conducted, indicating that the exposed groups exhibited lower exploratory behavior, higher anxiety behavior, and lower memory retention than the control groups. The difference was more pronounced in the soil leachate with acidified solvent, at both pH 5.2 and 3.6, suggesting that the combined effect of both stressors led to synergistic interactions, potentiating their impacts. Elemental analysis revealed elevated levels of neurotoxic metals, including Cr, Cu, and Ni, as well as the metalloid As, with acidification significantly enhancing their bioavailability. Moreover, our results demonstrate that acidification facilitated the mobilization of metals and the metalloid As, increasing their bioavailability and acting synergistically to exacerbate the behavioral impacts of contaminated soils. Special attention should be given to populations living in industrial areas that may be exposed to contaminated soils. Full article