Environments

17 pages, 4705 KiB

Open AccessArticle

Impact of Teachers’ Decisions and Other Factors on Air Quality in Classrooms: A Case Study Using Low-Cost Air Quality Sensors

by Zhong-Min Wang, Wenhao Chen, David Putney, Jeff Wagner and Kazukiyo Kumagai

Environments 2025, 12(8), 253; https://doi.org/10.3390/environments12080253 - 24 Jul 2025

Abstract

This study investigates the impact of teacher decisions and other contextual factors on indoor air quality (IAQ) in mechanically ventilated elementary school classrooms using low-cost air quality sensors. Four classrooms at a K–8 school in San Jose, California, were monitored for airborne particulate matter (PM), carbon dioxide (CO₂), temperature, and humidity over seven weeks. Each classroom was equipped with an HVAC system and a portable air cleaner (PAC), with teachers having full autonomy over PAC usage and ventilation practices. Results revealed that teacher behaviors, such as the frequency of door/window opening and PAC operation, significantly influenced both PM and CO₂ levels. Classrooms with more active ventilation had lower CO₂ but occasionally higher PM_2.5 due to outdoor air exchange, while classrooms with minimal ventilation showed the opposite pattern. An analysis of PAC filter material and PM morphology indicated distinct differences between indoor and outdoor particle sources, with indoor air showing higher fiber content from clothing and carpets. This study highlights the critical role of teacher behavior in shaping IAQ, even in mechanically ventilated environments, and underscores the potential of low-cost sensors to support informed decision-making for healthier classroom environments. Full article

(This article belongs to the Special Issue Air Pollution in Urban and Industrial Areas III)

► Show Figures

Figure 1

16 pages, 6542 KiB

Open AccessArticle

Effects of Dietary Exposure to Polystyrene Microplastics on the Thyroid Gland in Xenopus laevis

by María Victoria Pablos, María de los Ángeles Jiménez, Eulalia María Beltrán, Pilar García-Hortigüela, María Luisa de Saint-Germain and Miguel González-Doncel

Environments 2025, 12(8), 252; https://doi.org/10.3390/environments12080252 - 22 Jul 2025

Viewed by 28

Abstract

Plastic manufacturing involves using compounds that could be considered endocrine disruptors. Consequently, concern about the effect of these particles on the hormonal regulation of various systems, including the hypothalamic–pituitary–thyroid axis, has been increasing. By applying the Amphibian Metamorphosis Assay (AMA), the effects of irregular polystyrene microplastics (PS) MPs on the thyroid gland of Xenopus laevis were investigated. The histological effects on other organs of tadpoles were also studied. Tadpoles were exposed to 500 and 50 µg of virgin PS MP particles, (200 µm range)/L, administered by diet for 21 days. PS dietary exposure revealed statistically significant effects for the snout to vent length and the whole body length apical endpoints on day 21. The histological survey of both treatment groups revealed no noteworthy effects on the thyroid gland, digestive tract, or kidneys, but slight modifications to the liver. Mild ultrastructural modifications were detected in tadpoles’ enterocytes and hepatocytes in both treatment groups, but were likely to be reversible. Overall, our results contrast with previous research results in which effects were observed, but using different types, concentrations, and numbers of MPs. All this suggests the need for standardized methods for the environmental risk assessment of MPs/NPs (nanoplastics). Concern about the risk of NPs seems to be greater, and more studies with NP particles should be conducted. Full article

(This article belongs to the Special Issue Ecotoxicity of Microplastics)

► Show Figures

Figure 1

26 pages, 1894 KiB

Open AccessArticle

Illegal Waste Dumps and Water Quality: Environmental and Logistical Challenges for Sustainable Development—A Case Study of the Ružín Reservoir (Slovakia)

by Oľga Glova Végsöová and Martin Straka

Environments 2025, 12(8), 251; https://doi.org/10.3390/environments12080251 - 22 Jul 2025

Viewed by 26

Abstract

The aim of the article is to highlight the increasing environmental burden on aquatic ecosystems in Slovakia due to continuous pollution from municipal, industrial and agricultural sources. Laboratory analyses have shown alarming exceedance of the limit values of contaminants, with nitrate nitrogen (NO₃⁻) reaching 5.8 mg/L compared to the set limit of 2.5 mg/L and phosphorus concentrations exceeding the permissible values by a factor of five, thereby escalating the risk of eutrophication and loss of ecological stability of the aquatic ecosystem. The accumulation of heavy metals is also a problem—lead (Pb) concentrations reach up to 9.7 μg/L, which exceeds the safe limit by a factor of ten. Despite the measures implemented, such as scum barriers, there is continuous contamination of the aquatic environment, with illegal waste dumps and uncontrolled runoff of agrochemicals playing a significant role. The research results underline the critical need for a more effective environmental policy and more rigorous monitoring of toxic substances in real time. These findings highlight not only the urgency of more effective environmental policy and stricter real-time monitoring of toxic substances, but also the necessity of integrating environmental logistics into the design of sustainable solutions. Logistical approaches including the optimization of waste collection, coordination of stakeholders and creation of infrastructural conditions can significantly contribute to reducing environmental burdens and ensure the continuity of environmental management in ecologically sensitive areas. Full article

► Show Figures

Figure 1

Journal Menu

Journal Browser

Environments, Volume 12, Issue 8 (August 2025) – 3 articles

Further Information

Guidelines

MDPI Initiatives

Follow MDPI