Indoor air quality in a home improvement store: Gaseous pollutants, bioburden and particle-bound chemical constituents

• Assessment of indoor air quality of a popular home improvement and gardening shop. • Indoor PM 10 concentration of 45.4 ± 15.2 μg/m 3 during labour hours. • Ca was the most predominant metal with a concentration of 658 ± 297 ng/m 3 . • α-pinene was the most prevalent indoor VOC reaching 98 μg/m 3 at the wood section. • Fungi with clinical relevance and toxigenic potential were found. This paper provides a comprehensive assessment of indoor and outdoor air quality within a home improvement and gardening store chain in northeastern Portugal. In December 2021 and January 2022, two multipollutant systems were installed in the store and outdoors to assess air quality. Continuous monitoring included particulate matter below 10 µm (PM 10 ), CO 2 and comfort parameters. PM 10 samples were collected using gravimetric samplers during both occupied and vacant periods. These samples were then analysed for carbonaceous constituents and metal(loid)s. Additionally, volatile organic compounds (VOCs), carbonyls, bacteria, and fungi were passively sampled. Results showed higher indoor concentrations of PM 10 during labour hours (45.4 ± 15.2 μg/m 3 ), while outdoor values of 27.1 ± 9.96 μg/m 3 were recorded. The elemental characterisation of PM 10 revealed a high abundance of soil-related elements indoors, suggesting that resuspension is one of the primary sources. The most abundant elements were Ca, Fe, and Zn, with concentrations of 658 ± 297, 273 ± 141, and 172 ± 67.4 ng/m³, respectively. Outdoors, elements related to tyre and brake wear and road dust were predominant, indicating emissions from non-exhaust traffic emissions as the main source. A prevalence of α-pinene, limonene, and hexanal was found indoors, most likely related to wood products. Fungi with clinical relevance and toxigenic potential, and higher bacterial loads were observed in the gardening and heating sectors of the store. This study underscores the importance of investigating less-studied stores, as they may exhibit pollutant levels that exceed health protection thresholds.