Assessment of Indoor PM<sub>2.5 </sub>Concentration and Its Metal Compounds in Select Residential Dwellings in Antananarivo and Mahajanga Cities, Madagascar

Indoor air quality (IAQ) is crucial for human health, especially in urban areas where people spend most of their time indoors. In cities like Antananarivo and Mahajanga, Madagascar, various factors contribute to poor IAQ, posing significant health risks. A total of 26 samples were collected, comprising 16 samples from Antananarivo and 10 from Mahajanga. The concentrations of PM<sub>2.5</sub> and metallic trace elements (Aluminum (Al), Titanium (Ti), Chromium (Cr), Manganese (Mn), Iron (Fe), Nickel (Ni), Copper (Cu), Zinc (Zn), and Lead (Pb)) were analyzed using descriptive statistics. Statistical methods, including the Shapiro-Wilk test for normality, independent samples t-tests for comparing means between cities, and one-way ANOVA for analyzing site-to-site variation within cities, were applied to assess the data. The analysis revealed a variation in PM<sub>2.5 </sub>concentration ranging from 4.80 µg/m³ to 58.45 µg/m³, with a mean PM<sub>2.5 </sub>concentration of 24.39 µg/m³ across all sampling sites, with 68.75% of samples from Antananarivo and 50.00% from Mahajanga exceeding the World Health Organization (WHO) guideline of 15 µg/m³. The average concentrations of the metallic trace elements aluminium, titanium, chromium, manganese, iron, nickel, copper, zinc and lead were 0.6797 µg/m³, 0.0382 µg/m³, 0.0015 µg/m³, 0.0176 µg/m³, 0.4045 µg/m³, 0.0001 µg/m³, 0.0021 µg/m³, 0.0076 µg/m³ and 0.0023 µg/m³ respectively. The independent samples t-tests showed no statistically significant difference in mean PM<sub>2.5 </sub>concentrations between the two cities. However, the one-way ANOVA indicated significant variability in PM<sub>2.5 </sub>levels among different sampling sites within each city, highlighting spatial heterogeneity in indoor air pollutant concentrations. This study emphasizes the need for targeted, localized interventions to address disparities in indoor air quality and mitigate health risks associated with elevated PM<sub>2.5 </sub>levels in urban environment. The findings suggest that further research and policy efforts should focus on developing strategies to improve IAQ in Madagascar's urban areas to safeguard public health.