JUDY WOODRUFF: Finally tonight, special correspondent Cat Wise looks at how an insignificant-seeming bit of vegetation helped scientists in Portland, Oregon, discover air quality problems in certain areas of that city earlier this year.
It is part of our weekly series covering the Leading Edge of science and technology.
CAT WISE: Portland, Oregon, is a city that prides itself on its food trucks, bike-friendly streets, and being very focused on the environment. So, many people here were shocked when it was discovered earlier this year that certain neighborhoods had high levels of heavy toxic metals. That discovery was largely due to this woman and her love of moss.
SARAH JOVAN, U.S. Forest Service: Well, moss is kind of like the underdog of the plant world, in the sense that people tend to not really know what it is.
CAT WISE: Sarah Jovan is a research ecologist with the U.S. Forest Service. She and a small number of other scientists have been studying moss and lichens in forests for years to learn more about air quality.
That’s because moss and lichens are essentially little sponges that absorb everything in the air around them, including pollutants. But moss had never been studied extensively in an urban environment. So, several years ago, Jovan and a colleague decided they’d do just that in Portland. And they chose a type of moss that can be found nearly everywhere in the city. It’s called orthotrichum.
SARAH JOVAN: And what’s interesting is, it doesn’t seem to mind pollution at all. It’s like the Twinkie of the moss world, because it seems really indestructible.
CAT WISE: Jovan’s team took samples from 346 sites around Portland. They even climbed some trees. The samples were brought back to a Portland State University lab, where they were processed and cleaned of debris, and then they were sent off for a detailed chemical analysis.
The results that came back were startling. Moss from two neighborhoods contained high levels of cadmium, a metal which can cause a host of health problems, including kidney damage and lung cancer, if inhaled over a long time.
The cadmium hot spots, seen in dark orange on this Forest Service map, were right around two artisan glass manufacturing companies. And one location also had very high levels of arsenic. Cadmium, arsenic, and other metals are commonly used in glassmaking.
SARAH JOVAN: We knew we’d find some hot spots of pollution, but we were actually shocked. We found that the largest hot spot was associated with an industry that actually isn’t regulated for arsenic and cadmium.
And we said, oh, my gosh, you know, that’s an area where there are schools, there’s a day care, there’s neighborhoods.
CAT WISE: But she still had some big unanswered questions. Did the air in those neighborhoods also contain high levels of metals? Was the moss acting like an early warning system?
So, Jovan and her Forest Service colleagues shared their results with the state agency actually responsible for monitoring Oregon’s air, the Department of Environmental Quality.
SARAH ARMITAGE, Oregon Senior Air Quality Planner: To really know what people are breathing, we need to take these pieces of equipment out and run air through the filter, and then bring it back and analyze it.
CAT WISE: Sarah Armitage is a senior air quality planner for the state. She showed us some of the sophisticated air monitors that the agency deployed around the glass companies after they were given the moss study results.
Samples taken from those monitors, which were processed in this state lab, eventually confirmed that the air was indeed tainted. In some areas, cadmium levels were nearly 50 times above state health benchmarks, and arsenic were more than 150 times over.
The state had known for a number of years that there were elevated levels of certain metals in Portland’s air, but they were never able to pinpoint the sources. Prior to the moss study, there was just one permanent air monitor in Portland and air pollution was tracked on a regional scale, not neighborhood by neighborhood.
SARAH ARMITAGE: Cost. That’s really the reason. They are expensive to operate and to purchase and to do the analysis. An average site is about $150,000 per year.
But when we have the moss data, at least for metals, it screens a broad area, and we can zero in on a location where we know, if we put a monitor, we’re going to find some metals.
CAT WISE: But, costs aside, more air monitors simply weren’t required. Under the federal Clean Air Act, six common pollutants that cause smog and health problems have strict, enforceable emissions standards; 187 other pollutants, called air toxics, are also regulated, but they aren’t monitored to the same degree.
And Oregon, like many states, hasn’t been closely tracking industrial sources of cadmium and other air toxics or the health impacts.
MAN: New concerns about high levels of toxins in Portland neighborhoods.
CAT WISE: When the story broke, there was a big public outcry. Government officials held meetings with concerned residents. And the head of the state environmental agency resigned in March, soon after the moss results were made public, though he cited health concerns as the reason.
But the glass companies, which voluntarily suspended the use of the metals after the results came out, and have been working with the state since to comply with temporary rules, were not breaking the law, says air quality official Armitage.
SARAH ARMITAGE: As far as DEQ was concerned, and also the facility was concerned, they were in compliance.
We take responsibility for the federal standards. We put them in facilities’ permits. What wasn’t regulated was the furnaces that melted the glass. And that’s where the emissions were coming from.
MARY PEVETO, Neighbors for Clean Air: This idea that there’s this whole classification of air pollution that has not been well addressed by the federal government has been a really hidden secret really across this country.
CAT WISE: Mary Peveto is the co-founder of a local advocacy group which has been fighting for cleaner air more than a decade.
MARY PEVETO: As I have said, at the beginning, there was no credible evidence to demonstrate whether or not this company was emitting anything that was a problem.
CAT WISE: She gathered recently with a group of concerned residents who live near a metal manufacturing facility where the moss samples picked up elevated levels of nickel. The state now has air monitors deployed around that company too.
And Peveto says it’s about time.
MARY PEVETO: All of us have been really traumatized that our state would knowingly allow these toxics to continue to be in our environments, when we know that actions could have been taken to reduce them. These are the kinds of things that contribute to our health and disease in ways that you often don’t recognize.
CAT WISE: In fact, public health concerns have led to some significant changes. When an air monitor outside a day care near one of the glass companies detected a lead spike in May, Oregon’s governor issued an unprecedented temporary cease-and-desist order.
So far, state health officials say voluntary lead and cadmium testing in the community has not revealed an immediate widespread public health threat. But the long-term impacts are still being studied.
DR. KATRINA HEDBERG, Oregon State Health Officer: It’s always extremely difficult to associate one long-term health outcome like cancer with a very specific exposure.
CAT WISE: Dr. Katrina Hedberg is Oregon’s state health officer. I met up with her near the day care where the elevated lead levels were caught. She says one of the big lessons from the moss study is that better monitoring is needed, so that the public health community can gauge the actual risks from air pollution.
DR. KATRINA HEDBERG: I would say that, when there are more data, understanding what people are exposed to in various areas is useful, because that then helps us to determine what the level of risk is. We need data in the environment. Otherwise, it’s only theoretical.
CAT WISE: Oregon is currently revising regulations for glass manufacturers, and a major overhaul of permitting regulations for all companies which emit air toxics is also under way, with more input from health officials and the public.
For her part, scientist Sarah Jovan is continuing to monitor moss samples in the impacted neighborhoods, and she says she’s happy that moss is finally getting a little more respect these days.
For the PBS NewsHour, I’m Cat Wise in Portland, Oregon.
JUDY WOODRUFF: Current testing by the state of Oregon finds levels of airborne heavy metals detected by the moss have dropped substantially over the past year, since measures were taken to reduce their emission.