An oddball plant upends a state’s air pollution laws.

In the winter of 2013, lichenologist Sarah Jovan found herself driving a government minivan all over Portland, stopping many times with her colleagues to collect and bag not lichen, but moss. Orthotrichum lyellii, to be exact. Dark green and bushy, O. lyellii thrives on the trunks and branches of hardwood trees in the wet and overcast West Coast city. To the researchers, the homely species of moss was key to learning more about Portland’s air and the possible presence of chemicals that may harm human health.

Jovan is a research scientist at the Pacific Northwest Research Station and studies lichens and bryophytes—such as liverworts, hornworts, and mosses—and their roles as biological indicators of air quality. “People don’t tend to know much about them or notice them,” Jovan says. “But they are just fascinating. Moss are these beautiful little plants with leaves that are just one cell thick. I just like these oddball, lesser understood organisms.” Jovan’s winter moss sampling was part of an ambitious study that ultimately enabled the team to use moss data to produce fine scale maps of cadmium pollution, as well as other heavy metal pollution in Portland.

“As a lichenologist, I wanted to use lichens,” she says. “But there are areas in Portland where the air quality is compromised enough that even the most tolerant lichens don’t grow. What is neat about this moss is that it seems impervious to everything. It doesn’t mind growing right underneath the highway near a factory. It’s amazingly tolerant!”

On a request from the Oregon Department of Environmental Quality (DEQ), Jovan and her colleagues were on the lookout for high concentrations of cadmium in the city. Cadmium is a heavy metal used primarily in manufacturing nickel-cadmium batteries, and to a lesser degree in electroplating and producing pigments used in glass manufacturing. Exposure to cadmium can cause cancer and kidney disease. Back in 2011, Oregon DEQ monitors had sensed curious concentrations of cadmium in Portland’s air, but could not pinpoint its source.

Mining moss data

Scientists have used moss as biological indicators of air pollution since the late 1960s. Past studies have shown that levels of pollutants in moss correlate with atmospheric air pollution measured by instruments, suggesting that moss can complement existing networks of air quality monitors.

And because moss is plentiful in Portland, Jovan’s study would essentially take advantage of hundreds of fuzzy, green air quality monitors all over the city. Unlike most plants that absorb nutrients through their roots, moss have root-like filaments that merely anchor them to trees or rocks. Instead, the plants absorb nutrients and water from the atmosphere through their gametophytes—networks of stem-like and leaf-like structures. Mosses also do not have a protective epidermis, so they absorb water, nutrients, and pollutants like a sponge.

At the time of the study, the Oregon DEQ measured daily air pollution in Portland using one permanent air quality monitor and two mobile monitors. That they only had one permanent monitor in the city is not surprising. The instrument costs over $50,000 to operate per year. And with only one main and two mobile monitors, Oregon DEQ could only make air quality measurements in a region-wide scale. The instruments are just too few to make measurements that would point to the source of a pollutant. In contrast, Jovan and her colleagues were collecting multiple samples of moss all over Portland, so they anticipated being able to describe pollution levels at a much finer and detailed scale. “It would cost over $17 million to use instruments at the same spatial resolution as the moss,” Jovan says.

“We’re taking a snapshot,” Jovan adds. “Moss samples reflect several months to a year of air quality.” While air quality monitors can detect the presence of heavy metals and can plot trends in pollutions levels through time, moss data can help pinpoint sources of the pollutants. But it can’t tell us about potential health effects like a monitor can.

Jovan and her co-investigator Geoffrey Donovan, also of the Pacific Northwest Research Station, collected 346 samples of O. lyellii from sites randomly distributed on a 1-kilometer grid over the city. The researchers anticipated finding areas with high cadmium in moss once the samples were processed, and planned on collecting an additional 24 moss samples around the largest area.

They also collected other data, to rule out other variables. For example, because rain can wash off cadmium particles in moss, and temperature influences moss metabolism, the researchers collected temperature, rainfall, and humidity data. They recorded the genus of the trees they took samples from, as a coarse indicator of whether tree characteristics had a significant effect on pollutant levels in the moss.

To rule out unknown sources of cadmium, they gathered geographic data on likely sources of cadmium, such as electroplating and art glass manufacturing. Because vegetation can reduce air pollution, they also estimated the percentage of tree-canopy cover and grass-and-shrub cover in the area. And, to account for emissions that may not have been captured by other variables, they calculated the percentage of different land-use types in Portland, such as industrial, commercial, residential areas, and open spaces.

After three weeks of data collection from December 2 to 23, Jovan and her collaborators hunkered down in labs to process and analyze the data. The researchers sought help from the Oregon DEQ and Drexel University for data interpretation, while Portland State University provided lab space needed to prepare the moss for metals analysis. Forest Service researcher Vicente Monleon took charge of the statistical analysis. Demetrios Gatziolis, a Forest Service Geographic Information System specialist plotted the analyzed data onto a map.

“We imagined that we would find the highest values of cadmium closest to known pollution emitters—the big industrial facilities with the smoke big stacks,” Jovan says.

Instead, the researchers found two sources of high cadmium pollution not known to the Oregon DEQ as major cadmium emitters. Facilities that are known to use cadmium in Portland are mostly located in the north and northwest of the city. The moss data revealed cadmium hotspots elsewhere: in the southeast and northeast quadrants. They also found over a dozen smaller areas of interest in various neighborhoods, including several with relatively high levels of top priority metals–such as arsenic, chromium, cobalt, nickel, and lead–in moss.

“That was a shock,” Jovan says.

Hotspots and a bullseye

With the modeling results in hand, the team created a map predicting cadmium levels using a standardized scale.  Most of the city glows green, indicating low cadmium in moss. The city is peppered with black dots, marking where the researchers collected moss samples. But right in the southeast glowed an orange blob surrounded by yellow, indicating high cadmium levels over an art glass manufacturer called Bullseye Glass. A slightly less intense orange blob hovered over the east of Fremont Bridge which seemed to correspond to Uroboros Glass Studio.

To confirm the results, the researchers looked at the selenium and arsenic levels in their moss samples, as both are used in art glass manufacturing. They found selenium and arsenic hotspots right over Bullseye Glass.

“Cadmium is used as the red pigment in glass so that’s partially how we made that discovery,” Jovan says. “Additionally, we went back in and collected another moss dataset near Bullseye Glass, which also confirmed that that facility was likely the main emitter. At that point, we thought this could be bad.”

The researchers discussed their findings with the Oregon DEQ because they still needed measurements from their air quality monitors to determine whether the cadmium emissions from the two moss hotspots were indeed at levels harmful to human health.

“Moss data are an indicator, but that doesn’t mean there’s a health problem,” Jovan says. “All of the health thresholds for heavy metals are written in terms of what the Oregon DEQ monitors measure. That’s how we crosswalk from the moss to ‘This is actually dangerous for people.’”

Oregon DEQ put a monitor right across the street from Bullseye Glass. “Their monitor got these astronomical values,” Jovan says. “Cadmium levels were 49 times the health benchmarks.” The monitor also found arsenic levels 155 greater than health benchmarks. Bullseye Glass was near two schools, a daycare center, and a large residential area.

Evidence pointing to Uroboros Glass as the source of the smaller cadmium hotspot was not as strong. However, Uroboros, like Bullseye, did not filter emissions from their glass furnaces. How was it possible that both companies were emitting high or dangerous levels of cadmium, and yet stayed undetected by state air pollution monitors?

Regulations and loopholes

According to Jovan, Bullseye Glass was operating under conditions set by state and federal air quality regulations, which allowed them to operate without emissions controls on their glass furnaces, and did not require emissions testing for the metals used. Uroboros did not produce enough glass to require a permit.

“Both companies were in compliance with the law when this was happening,” Jovan said. “And that’s part of what made this such a scandal.”

The study findings rattled Jovan. “I guess a lot of our air toxics regulations are not very protective, honestly. The regulations are based on some cost benefit analysis of what pollution control technology can be obtained,” she said. “It’s weird. I always thought the rules were based on risk to human health. I think many Portlanders were startled to realize that this isn’t always the case.”

The local news media broke the story on Jovan’s and the Oregon DEQ’s findings, and soon national and international news outlets were sounding the alarm on Portland’s cadmium pollution.

“The science of it has been pretty clear cut. The hard part has been the fallout,” Jovan says. “When the story broke, there was an intense media response. And there were community meetings at a couple of schools near the two glass manufacturers that were just packed full of upset people and a lot of folks who felt like their health had been harmed—even some children. That was heart wrenching.”

In the middle of the fracas, Bullseye Glass voluntarily stopped using cadmium and arsenic, and Uroboros Glass—which hadn’t used arsenic in two decades—voluntarily stopped using cadmium. From February 9 to 27, 2016, atmospheric cadmium outside Bullseye Glass was measured at 1.1 nanograms per cubic meter, which is 1.8 times the state benchmark. This is an improvement over measurements made in October 2015 when atmospheric cadmium was measured at 29.4 nanograms per cubic meter. Arsenic was measured at 0.94 nanograms per cubic meter on February 2016, a vast improvement on 31.7 nanograms per cubic meter measured on October 2015.

Over at Uroboros Glass, the average atmospheric cadmium from February 20 and February 27, 2016 was measured at 0.67 nanograms per cubic meter. The Oregon DEQ did not monitor the facility in October 2015. However, the Environmental Protection Agency had placed an air quality monitor from August 23 to and November 3 in 2009 at Tubman School, located 278 meters from Uroboros. The EPA monitor measured an average atmospheric cadmium concentration of 7.29 nanograms per cubic meter.

Six months after they stopped using cadmium in their facility, Bullseye Glass installed pollution controls in its facility. A month after that, Oregon DEQ released permanent pollution control rules for all art glass manufacturers in Portland (they had previously released temporary “emergency” rules in the spring). Two months after that, the owners of Uroboros Glass cited the cost of complying with new environmental regulations as one reason for discontinued operations. The company was eventually sold to a new owner in California and the facility was transferred to Mexico.

When science collides with policy

Jovan’s groundbreaking moss study continues to affect air pollution regulations and public opinion in Portland and beyond. Brian Boling, Oregon DEQ’s laboratory program manager, says the agency had been hard at work rewriting regulations for art glass manufacturers in the state.

“The new rules are final and are now in place,” he says. “The biggest among the changes concern the use of bag houses.”

Bag houses, also known as fabric filters, are air pollution control devices that filter out particulate matter from furnaces by passing the dirty air through a cloth layer. According to Boling, all colored art glass manufacturers in Oregon are now required to install bag houses in their facilities.

Oregon DEQ has also started to phase in the use of moss in their monitoring. “I’ve looked at moss as a good scanning tool to see if an area has something that we really want to spend more resources on or seeing if there is really is an issue,” Boling says. “Now, we’re working on bringing the methodology up in our own lab and how we would use it into the future.”

In addition, the governor of Oregon has asked for sweeping reform to reduce this kind of air pollution. She created a program called Cleaner Air Oregon, which proposes health-based standards for reducing air toxics like those emitted by Bullseye Glass. It aims to close gaps in the regulations that allowed industrial plants to operate legally but still emit pollutants at levels that could harm people’s health. The draft Cleaner Air Oregon rules are available for public comment until December 22, 2017.

The impact that Jovan is happiest about is that air quality has improved around where the cadmium hotspots used to be. This development has drawn other cities to the advantages of air quality monitoring by moss. Seattle, Cincinnati, Vancouver, and other cities are interested. On a much larger scale, news about Jovan’s study also motivated the EPA to review glass manufacturers all over the United States and to tighten enforcement.

“It’s been incredible,” Jovan says. “Suddenly, moss is very popular.”

And even as the ripples created by Jovan’s cadmium study are still fanning out, the researcher has gone back work, looking at how the moss measurements compare with air monitor measurements at eight sites across Portland. The 14-month study aims to determine the accuracy of moss data. Using data from that collection of moss in the winter of 2013, Jovan is also studying emissions sources for lead patterns observed across the city.

She still gets a lot of calls about her cadmium study, and often cars in Portland will remind her of how big it became. Jovan says, “I’ve seen this bumper sticker around town. It says, ‘Moss don’t lie.’”

Originally published in Science Findings. Download the publication here.