Characteristics and exposure determinants of PM2.5, formaldehyde, and total volatile organic compounds in residential indoor air in Korea.

Indoor air pollutant levels can be affected by both internal and external factors. However, most epidemiological studies have focused on outdoor air pollution. Here, we aimed to provide nationally representative data on residential air quality in Korea and to identify the determinants of residential air quality. We conducted an indoor air quality study in 1182 households nationwide from July 2020 to August 2021 based on the Korean National Health and Nutrition Examination Survey. In addition to the questionnaire conducted with occupants, we measured indoor PM2.5, formaldehyde, and total volatile organic compounds (TVOC). Outdoor PM2.5 concentrations were obtained from the Air Korea portal (airkorea.or.kr). The geometric mean residential concentrations of PM2.5, formaldehyde, and TVOC were 13.1 (1.9), 20.5 (2.1), and 93 (4.2) μg/m3, respectively, with the values in parentheses indicating geometric standard deviations. Various residential factors are associated with residential air pollutants. Indoor PM2.5 levels were considerably associated with outdoor PM2.5 and indoor carbon dioxide (CO2) concentrations, season, indoor smoking, house size, gas fuel use for cooking, and use of air cleaners. Indoor formaldehyde levels were substantially associated with indoor CO2 concentrations, season, house size, residential period, and air cleaner use. Indoor TVOC were significantly associated with indoor CO2 concentrations, floor level of residences, house size, residence time, house renovation within the previous 6 months, and use of diffusers. Factors associated with ventilation were positively correlated with indoor PM2.5 and negatively correlated with indoor formaldehyde and TVOC. Our results are useful for understanding and managing residential air quality.