Air pollution is an invisible threat in our urban environments, heavily impacting cardiovascular and respiratory systems and standing as the single largest environmental cause of disease and premature death globally.
Often, monitoring the heavy metals and particulate matter that fill city air involves expensive equipment, heavy use of chemical reagents, and time-consuming laboratory preparation. However, researchers in Chicago have been exploring a much cheaper, greener alternative that might already be growing nearby: moss. The full research is available in the open-access, peer-reviewed journal BioRisk.
Because mosses lack true root systems, they absorb the vital nutrients they need to survive, along with any environmental contaminants, directly from the atmosphere, making them exceptionally effective living records of long-term air pollution.
To test the viability of this biological monitoring, the team systematically deployed small, one-gram mesh bags of carefully cleaned Sphagnum moss across various locations in the Chicago area.
The scientists strategically hung these “green guardians” in diverse environments, including an industrial metals recycling facility, a marshland corridor, a commuter railroad station, and a semi-natural reference area in Lake County.
In a direct test of vehicle emissions, they even taped several moss bags straight to the exhaust pipe of a diesel truck. After leaving the moss bags exposed to the urban elements for roughly three to four weeks, the team brought them back to the lab, crushed them into a homogeneous powder using liquid nitrogen, and analyzed them using portable X-ray fluorescence (pXRF) technology
The living monitors proved incredibly adept at capturing location-specific pollution footprints. Unsurprisingly, the moss placed near the metals recycling facility showed elevated levels across all the measured heavy metals, acting as a clear multi-metal emission source. The bags stationed near the commuter railroad exhibited significant spikes in iron, a likely consequence of the friction and wear on the steel rail infrastructure.
Alarmingly, even the moss placed in the semi-natural Lake County area absorbed elevated concentrations of nickel, demonstrating that pollution from a major highway less than one kilometer away can travel far into a seemingly pristine environment.
Furthermore, the moss bags directly attached to the diesel truck showed a rapid accumulation of metals like iron, zinc, copper, titanium, and manganese within just three days, though a heavy Chicago rainstorm on the fourth day washed some of that accumulated particulate matter away.
Ultimately, this exploratory study demonstrates that combining simple moss bags with portable X-ray technology can serve as a highly accurate, cost-effective alternative to conventional air monitoring. Since the preparation is cost-effective and the screening process is relatively quick, this methodology has the potential to make environmental science more affordable and accessible; therefore, this study warrants further research.
Moving forward, resource-limited communities that are disproportionately burdened by poor air quality could utilize these green guardians to document local contamination hotspots. By doing so, they can gather the vital data needed to fiercely advocate for environmental justice, targeted remediation, and healthier urban spaces for everyone.
Original source:
Campbell T, Gwilliam III GF, Evans NM, Peltz K, Simpson G, Dussubieux L, Erazo E, Guare K, Krechner A, Long E, Maari S, Oguike I, Rice K, Zinke A, Christian C, Qazi-Lampert A, Henkin JM, Kreider D, Maves C, Merrill G, Moy P, Rodriguez Y, Ryan Z, von Konrat M (2026) Green guardians: Mosses as potential low-cost biomonitors of air pollution in urban Chicago. BioRisk 24: 55-67. https://doi.org/10.3897/biorisk.24.180507
