The variation in exposure to ambient formaldehyde at different times of the year in various countries: A systematic review and meta-analysis

Exposure to ambient formaldehyde can be associated with hazardous consequences. It can be affected by seasonal and meteorological parameters. This study was performed to investigate the variation in exposure to ambient formaldehyde at different times of the year in various countries. A literature search was performed in five databases of Scopus, PubMed, Web of Science, Medline, and Embase. The search strategy was based on PRISMA protocols. The pooled values of ambient exposure to formaldehyde were computed by meta-analysis for all seasons. 44 articles were evaluated in this study. Based on the results, the concentrations of exposure to this substance in 13 of 20 studies in spring (65.00 percent), 29 of 38 studies in summer (76.32 percent), 12 of 17 studies in autumn (70.59 percent), and 15 of 37 studies in winter (40.54 percent) were higher than permissible value recommended by Texas Commission on Environmental Quality (3.3 µg/m³) for long exposure. The highest concentration of exposure to ambient formaldehyde was observed in Iran (23.93 µg/m³) in spring, in China (26.38 µg/m³) in summer, in China (15.0 µg/m³) in autumn, and in China (45.56 µg/m³) in winter. The pooled concentrations (μg/m³) of formaldehyde in spring, summer, autumn, and winter seasons were estimated as 5.78 (95 % CI: 4.82–6.75), 6.57 (95 % CI: 5.85–7.29), 6.07 (95 % CI: 4.76–7.39), and 3.59 (95 % CI: 3.17–4.01), respectively. The concentrations of formaldehyde in environmental settings tend to be mostly higher during the summer compared to other seasons. Perception of the fluctuations in formaldehyde concentration due to seasonal and meteorological changes is beneficial for air quality management.