Bryophytes as Living Markers for Air Pollution Monitoring: A Review

Air pollution is a major environmental challenge with significant impacts on ecosystems, biodiversity, and human health. Conventional atmospheric monitoring depends largely on instrumental networks, which can be expensive, infrastructure-intensive, and limited in spatial coverage. Bryophytes, particularly mosses, have emerged as useful biological indicators because their exposed surfaces, poorly developed cuticles, and ability to retain airborne particles and accumulate atmospheric contaminants allow them to integrate pollution over time. This review examines the potential of bryophytes as biological indicators and living sensors for monitoring atmospheric pollution, with emphasis on heavy metals, nitrogen, particulate matter, polycyclic aromatic hydrocarbons, persistent organic pollutants, and emerging contaminants such as airborne microplastics. Evidence from both passive biomonitoring using naturally occurring mosses and active biomonitoring using standardized moss-bag techniques is evaluated. Studies conducted at local, regional, and continental scales demonstrate that bryophytes can reveal spatial pollution patterns, identify contamination hotspots, track temporal changes, and indicate influences from industrial and traffic-related emissions. However, differences in species characteristics, environmental conditions, canopy effects, exposure duration, sample preparation, and analytical procedures can affect pollutant accumulation and limit comparisons among studies. Greater methodological standardization and integration with instrumental monitoring are therefore needed to improve data reliability and comparability. Overall, bryophyte-based biomonitoring offers a simple, cost-effective, and environmentally compatible approach for assessing atmospheric deposition and mapping pollution patterns, particularly across areas where conventional monitoring networks are sparse.