Lichens and Mosses as Biomonitors of Indoor Pollution

SIMPLE SUMMARY: Human exposure to pollutants in indoor environments is a relevant health concern. Long-term monitoring data in indoor environments are largely missing due to a lack of adequate measuring devices. Biomonitoring (the use of living organisms to identify/assess potential hazardous exposure to chemicals and their effects) can provide useful information on indoor air quality and effects. Given their ability to intercept pollutants from the atmosphere, lichens and mosses are commonly used as outdoor biomonitors of atmospheric pollution by potentially toxic elements. Their application in indoor environment is recent but represents a promising output of the scientific research. In this review, indoor biomonitoring studies carried out using mosses and lichens have been compared, and critical issues and open matters have been underlined, as well as future perspectives related to their fruitful application in indoor environments. This review highlights the peculiarities of each study and the need for the development of shared harmonised protocols. ABSTRACT: Biomonitoring in indoor environments is a recent application, and so far, indoor air quality (IAQ) has been investigated only in a few cases using photosynthesising biomonitors. On the whole, 22 studies have been selected and reviewed, being specifically focused on the assessment of IAQ using biomonitors, such as lichens (9 papers), mosses (10), or their combination (3). In general, indoor samples face an altered light regime, ventilation, and a reduced hydration, which should be taken into consideration during the design and implementation of indoor monitoring. This review highlights critical issues (and some solutions) related to sample devitalisation (moss), hydration during exposure, preparation of the exposure device (mostly lichen and moss bags), duration of the exposure, post-exposure treatments, assessment of the vitality of the samples, as well as data elaboration and interpretation. This review evidences the feasibility and usefulness of lichen/moss monitoring in indoor environments and the need to develop standardised protocols.