## 1 Introduction  
Air pollution remains a serious global environmental and public health safety challenge of the 21 st century. Recent studies indicate that 99% of the world's population is exposed to particulate matter (PM) concentrations exceeding World Health Organization (WHO) safety limits, with ambient (outdoor) and household pollution collectively contributing to 6.7 million premature deaths annually through cardiovascular, respiratory, and oncological issues [1, 2, 3]. The economic burden is equally severe, with global welfare lossesestimated at USD 8.1 trillion (6.1% of GDP), and it is driven by healthcare expenditures and productivity declines [4]. The Air Quality Index (AQI) is a standardized measure used globally to communicate the level of air pollution or the potential for pollution. It translates complex air quality data into a single number and a color code, ranging from 0 (good) to 500 (hazardous), making it easier for the public to contemplate the health risks associated with pollutants such as PM\({}_{2.5}\), PM\({}_{10}\), O\({}_{3}\), and NO\({}_{2}\)[5]. Table 1 below shows that AQI categories directly correlate with population health risks, and this guides public advisories and policy interventions during pollution episodes [6]. Regarding AQI monitoring, IQAir is a leading company in air quality monitoring. It offers IoT devices and services that track air quality. Their range of outdoor sensors enables the monitoring of pollutants such as PM\({}_{10}\), PM\({}_{2.5}\), and CO\({}_{2}\), as well as the temperature and humidity. These sensors can also be integrated with the IQAir Map platform, a real-time, interactive map that visualizes air pollution levels, as well as a corresponding mobile phone application [7]. Similarly, Clarity Node-S is an industrial-grade, solar-powered, and cellular-connected IoT sensor that measures key pollutants, such as PM\({}_{2.5}\), NO\({}_{2}\), and ozone, in real time [8]. In Greece, urban centers, like Athens, Thessaloniki, and Ioannina, face persistent air quality challenges, with winter PM\({}_{2.5}\) and PM\({}_{10}\) levels often exceeding WHO guidelines by 300-400% due to vehicular emissions, house heating, and trans-boundary pollution [9; 10; 11; 12; 13; 14]. For instance, Ioannina's annual PM\({}_{2.5}\) average of 20 ug/m\({}^{3}\) in 2023 surpassed the WHO annual guideline (5 ug/m\({}^{3}\)) by 300% [15] and the EU limit value (10 ug/m\({}^{3}\)) by 100% [16], reflecting cooperative impacts from local biomass-wood combustion (contributing to 60-70% of winter PM\({}_{2.5}\)) and long-range Saharan dust transport [14; 17; 18]. Although this study focuses on Greece, worldwide elevated PM levels pose a global public health threat. For example, cities like Delhi and Lahore consistently exceed WHO PM\({}_{2.5}\) guidelines by 10-50 more particle concentrations during winter months due to factors such as vehicular emissions, industrial activity, coal-fired heating, and agricultural residue \begin{table}
\begin{tabular}{c c c c} \hline \hline
**AQI Range** & **Category** & **Color Code** & **Health Implications** \\ \hline
0–50 & Good & Green & Air quality is considered clean with minimum dist or particulate matter. \\
51–100 & Moderate & Yellow & Acceptable; some pollutants may affect a few particularly sensitive individuals. \\
101–150 & Unhealthy for Sensitive Groups & Orange & Members of most sensitive groups may experience health issues. Nevertheless, the general public is unlikely to be affected. All groups (sensitive–non sensitive) may begin to experience health effects. Sensitive groups may experience them more severely. \\
201–300 & Very Unhealthy & Purple & Health alert: everyone may experience serious health effects. \\
301–500 & Hazardous & Maroon & Health warnings of emergency health conditions. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: EPA Air Quality Index (AQI) categories and health implications. burning in nearby regions [19; 20; 21].