Assessment of human exposure to terpenes from fragrant plants in homes using passive sampling

The air quality benefits of indoor plants are widely recognized, but their capacity to emit volatile organic compounds (VOCs) such as terpenes remains less explored. This research quantifies the impact of a common fragrant household plant, Plectranthus tomentosa, on indoor terpene levels within residential environments. The emission characteristics of terpenes from potted and hydroculture plants were investigated using PTR-TOF-MS in a controlled chamber, and exposure levels in residential environments were assessed using passive sampler (ePTFE PS). Deploying fragrant plants, particularly hydroculture plants, led to a substantial elevation of indoor terpene concentrations. In 30 homes, hydroculture plants increased average limonene and α-pinene concentrations by 2.3 and 2.5 times, respectively, over 3 h. Our findings demonstrate that fragrant plants, particularly when hydroculture, act as a significant source of limonene and α-pinene. In contrast, the plants exhibited negligible removal efficiency for BTEX compounds. The mean estimated daily exposure dose (DED) for limonene inhalation in infants was 45.4 µg/kg/day, which was significantly higher than that in adults at 13.7 µg/kg/day when deploying hydroculture plants. These results suggest that fragrant plants should be carefully selected and managed, especially in indoor environments where sensitive individuals are present.