Lichens reveal the quality of indoor air in Selangor, Malaysia

Background Indoor air quality (IAQ) is a concern in kindergartens as children spend much of their time there. Yet, there is a shortage of biological indicators needed for assessing IAQ. Thus, this study evaluated IAQ using transplanted lichen Usnea misaminensis as a biological indicator. Methods Lichen samples, collected from Bukit Larut, Perak, Malaysia, were exposed to indoor and outdoor environments in an urban area (Ummi Aiman Kindergarten) and a rural area (Ummi Qaseh Pelangi Kindergarten) for 2 months during August 15 to October 14, 2019. The concentrations of 12 selected elements and the vitality of the lichens were then evaluated. Results Increased concentrations of eleven of the twelve elements deposited in the lichen samples in both urban and rural areas were observed. For both areas, the element concentrations in the samples from the indoor environment was lower than those from the outdoor environment, and those in the rural area were lower than those from in the urban area, suggesting the impacts of traffic emissions. The vitality of the lichens showed no significant change in indoor environment, compared to that in outdoor environment, indicating that even exposed to indoor environment, the lichens remained effective biological indicators as same as they were in the outdoor environment. Conclusions Lichens are effective biological indicators for both outdoor and indoor environments. Furthermore, outdoor emissions could influence IAQ, which could be problematic in densely populated areas such as kindergartens. Mitigation measures should be taken.