2019 Yes https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6571755/ Paoli, Luca Europe Observational Modeling Elementary (K-5) Middle/Jr High (6-8) High School (9-12) Biomonitoring Chlorophyll fluorescence Citizen science Evernia prunastri Exposed to control ration Indoor pollution   he content of heavy metals increased in samples exposed outdoors for 11 out of 12 elements (Al, As, Cd, Cr, Cu, Fe, Pb, S, Sb, V and Zn, but not Ca) in the urban area and for 5 (As, Cd, Cu, Pb and Sb) in the rural area. Indoor concentrations were overall similar, both in rural and urban buildings, independently of the outdoor conditions. An indoor accumulation occurred only for Cd, Cu and Pb. An indoor origin was suggested for Cd, while for Cu and Pb, outdoor penetration (car traffic) is the likely cause of indoor values. Indoor exposed lichens maintained their vitality (as reflected by chlorophyll a fluorescence emission). This latter result further supports the use of lichen biomonitoring as a suitable method for assessing IAQ.