U.S. Forest Service
U.S. Forest Service
Led the first-ever study using tree moss to detect air pollution in a major city, including cancer-causing heavy metals, prompting enforcement actions and offering a new, cost-effective way to identify threats to public health
Environmental officials in Portland, Oregon, knew something was amiss several years ago when they found toxic heavy metals in the air, but they couldn’t figure out where the pollution originated.
Enter Sarah Jovan, a research ecologist, and Geoffrey Donovan, a research forester. The two U.S. Forest Service employees started chatting about these findings and how moss can be used to detect air quality problems in forests—a conversation that led to applying this novel concept for the first time in a city.
Their collaboration, which began in 2013, led to startling results. The moss from tree trunks and branches was used as a test bed at 346 sites throughout Portland, allowing Jovan and Donovan to produce maps showing heavy metals at a level of detail never seen before. The tests revealed numerous hot spots in residential neighborhoods near two stained glass manufacturers that had high and potentially dangerous levels of cadmium and arsenic, both of which can cause cancer.
“It was groundbreaking work,” said Sarah Armitage, senior air quality planner at Oregon’s Department of Environmental Quality. “I don’t know if we would have figured out the source of our heavy metals without them. It might have taken us years longer.”
The disclosures in June of 2016 led to follow up air quality testing by Oregon’s environmental department that found cadmium 49 times and arsenic 155 times above acceptable health levels. Although the heavy metals are used in stained glass, a loophole in state and federal regulations had allowed the emissions to go unchecked.
The revelation led to tighter monitoring and regulation of glass manufacturers in Portland and the state. Factories installed new filters, and the two companies emitting the air pollution stopped working with cadmium. Armitage said the moss study was a “tipping point” that led to more state funding to conduct extensive air quality monitoring.
And in response to the data from the moss program, the federal Environmental Protection Agency reviewed glass manufacturers across the country and tightened enforcement.
“What was neat about it was that the EPA said, ‘Oh, we might be missing something here. Let’s take a look at all these types of industries across the country and see if we missed anything,’ ” said Andrew Gray, research ecologist at the Forest Service Pacific Northwest Research Station. “So there was a Portland impact, but a much bigger impact as well.”
In addition, the Portland experience has led to interest by Cincinnati, Seattle and other cities, in using this technique to monitor their air quality because of its effectiveness and low cost. Air quality instruments cost an average of $50,000 each to operate on an annual basis, which translates into $17 million a year to deploy monitoring devices with the same reach as the Portland moss sampling grid. The Portland moss study, in contrast, cost $100,000.
Following the revelations from the testing performed by Jovan and Donovan and later by the state, there were warnings issued in Portland against eating food from local gardens, and health screenings were made available for local residents.
“What I think is most significant is that it made a real difference in people’s lives,” Jovan said.
Jovan and Donovan’s team also trained state regulators to do moss testing of their own to pinpoint emissions problems before deciding where to deploy expensive air monitors.
One big complication Jovan and Donovan faced was the firestorm of political and public interest their moss results set off. They were bombarded with press calls, spent hours explaining the air problems in public meetings and still needed to finish their research.
“A 10-year-old has kidney cancer and is asking if that is what caused the cancer. How do you deal with that?” Donovan asked.
Colleagues said the pair handled the stress and public concern well.
“One of the challenges in dealing with the sensitivity of the information was that everyone wanted the results yesterday,” Gray said. “Sarah and Geoffrey were really under the microscope and attending really contentious public meetings, trying to explain what they found to all sorts of regulators and politicians.”
Although the air has improved because of the moss study and because better monitoring is now done in Oregon, the work is not over.
Jovan is studying how to calibrate the moss results to specific levels of toxins in the air. She’s also looking at data showing high levels of lead in certain neighborhoods and trying to find the cause.
Donovan is on sabbatical in New Zealand this year looking at how the natural environment affects children and whether trees can reduce exposure to pesticides.
The moss study, he said, shows the value of good government science.
“We had a modest amount of funding and luckily the freedom to follow our noses,” he said. “Lots of times that comes to nothing. This is an example of the good things that can happen if you have that unique environment.”