## 2 Materials and Methods  
The samples were collected between February 2021 and January 2022 from 3 different departments (sweets, detergents, and plastics) of a general store and the air from outside (on the parking side of the shop). The store is located in western Romania, Resita town (coordinates latitude 45 deg19'15'' N, longitude 21 deg52''02'' E; Figure S1). The store's location prevents interference of the city center as much as possible. The general store has different departments. The sweets department is located on the west side, the detergents in the middle, and the plastics on the east side. The departments in the store are almost the same size. The sampling (using the analyzer and passive sampling with tubes) was taken from every department at a level of 1 m from the floor and as much as possible in the middle of the department. The sampling occurred in the store's parking lot 10 m from the entrance door for the outside measurements. In order to consolidate and match the analyzer determinations with passive sampling (which has 30 min of sampling in tubes), the measurements took 30 min, and the reading was performed after stabilization. Every month, four measurements were taken at the same hour (at noon) and on the same day (Wednesday). The measurements for total volatile organic compounds, PM1, PM2.5, PM10, and formaldehyde, were taken with a Diemmern DM 106 (Shenzhen Diemmern Testing Technology Co., Ltd., Shenzhen, China) professional air analyzer and the Honeywell MultiRAE (Sunnyvale, CA, USA). For all determinations, the detection limit was 1 ug/m\({}^{3}\). The analysis of lactic acid, benzene, ortho and para-xylene, toluene, and monoterpne was carried out using gas chromatography-mass spectrometry. The method follows the same procedure as in [PERSON] et al. [43] with small modifications. A sample volume of 6000 mL was obtained using a constant airflow from a sample pump (model 210-1003 MTX; SKC Inc., Houston, TX, USA) at a rate of 200 mL per minute. This pump was employed for the sampling of volatile organic compounds. Stainless steel cartridges (10.5 cm length, 4 mm inner diameter; Supelco, Bellefonte, PA, USA) containing Carbotrap C 20/40 mesh (0.1 g), Carbotrap B 40/60 mesh (0.1 g), and Carbotrap X 20/40 mesh (0.1 g) adsorbents (Supelco, Bellefonte, PA, USA) were utilized for the quantitative analysis of airborne volatiles. An automated cartridge desorber and a Shimadzu 2010 Plus GC-MS apparatus (Shimadzu Corporation, Kyoto, Japan) were used to analyze the adsorbent cartridges. For tube desorption, the helium purge flow was set at 40 mL min\({}^{-1}\), the primary desorption temperature at 250 \({}^{\circ}\)C, and the primary desorption time was 6 min. The cold trap had been set to \(-\)20 \({}^{\circ}\)C. A capillary column, OPTIMA-624 (0.25 mm i.d., 60 m length, 1.4 \(\upmu\)m film thickness; Macherey-Nagel, Duren, Nordrhein-Westfalen, Germany), was utilized for the separation of compounds. The mass spectrometer operated in electron-impact (EI) mode at 70 eV, with a scan range of 38-600 \(m/z\). The transfer line temperature was set at 250 \({}^{\circ}\)C, and the ion-source temperature at 200 \({}^{\circ}\)C. Compound identification was carried out using the NIST spectral library ver. 14. Quantifying various compounds followed the earlier detailed procedure [44]. One-way ANOVA and [PERSON]'s multiple comparisons test used the GraphPad Prism version 10.0.0 for Windows (GraphPad Software, San Diego, CA, USA, www.graphpad.com) (accessed on 11 November 2023). Data were considered significantly different for \(p<0.05\)). Continuous variables were compared using the 2-way ANOVA test or Mann-Whitney test, depending on the normal or abnormal distribution of data. A \(p\)-value \(<0.05\) was considered statistically significant. In the figures, data marked with distinct letters are considered significantly different (\(p<0.05\)), whereas data sharing identical letters are not deemed significantly different (\(p>0.05\)).