Common moss could "revolutionize" air pollution regulation and oversight, according to a new study whose findings have already yielded dramatic results in the Pacific Northwest.
The existing U.S. network of air monitors "may not be able to identify some important sources of atmospheric pollutants that do not disperse far from their emission source," researchers say in the study, posted online Tuesday in Science of the Total Environment. "Moss is a low-cost way of mapping air pollution and has the potential to revolutionize the enforcement of environmental regulations."
The research team — led by two employees of the Forest Service’s Pacific Northwest Research Station in Portland, Ore., and including other scientists from the service and Drexel University — launched the study in 2013, using moss harvested from hardwood trees around Portland.
While their original concern was with hydrocarbons produced by burning wood and fossil fuels, the researchers expanded their focus to include heavy metals because the laboratory analysis was "relatively inexpensive," the Forest Service said a news release.
The team found moss was a "bioindicator" of cadmium, a heavy metal linked to cancer and kidney disease, and uncovered pollution "hotspots" in the city near two stained glass factories.
The researchers alerted the Oregon Department of Environmental Quality, which followed up last fall with air monitoring near the factories that found mean cadmium concentrations were 49 times higher than the state’s benchmark.
In the resulting public outcry, the department’s chief resigned last month, citing health reasons. Yesterday, Oregon Gov. Kate Brown (D) named a new acting director and unveiled a program to strengthen oversight of industrial air pollution.
Both factories have stopped using cadmium. While it’s not known exactly how long heavy metals persist in moss, the researchers are now taking weekly samples near the factories to "quantify how cadmium, and other heavy metals, are lost from moss tissue," the study says.
The air monitoring gaps exposed by its findings are not unique to Portland, it adds.
The results show that moss can serve "as a screening tool to help cities strategically place their air-quality monitors," Sarah Jovan, the research scientist who helped lead the study, said in the release.
The heavy metals moss analysis cost $50 per site, Jovan added, low enough to make it possible "to sample extensively and flag hotspots for follow-up instrumental monitoring."