Urban Moss in Older Portland, Oregon, Neighborhoods Reveals Alarmingly High Lead Levels

The United States has a legacy of lead contamination that could be affecting the environment around your home.

A new study found that moss in older neighborhoods in Portland, Oregon, had lead levels that were much higher than in nearby rural areas due to lead-sheathed telecommunications cables and leaded gasoline.

In pre-1960 Portland neighborhoods, the cables were common and are still in place in some cases, though they are not being used anymore, said Alyssa Shiel, lead author of the study and an environmental geochemist and associate professor at Oregon State University (OSU)’s College of Earth, Ocean, and Atmospheric Sciences, in a press release from OSU.

^{Lead levels in moss are up to 600 times higher in older Portland neighborhoods where lead-sheathed telecommunications cables were once used, compared to lead levels in rural areas. Alyssa Shiel, Oregon State University}

“Lead across the city is largely the result of historical leaded gasoline use, nearly 30 years after it was banned in 1996,” Shiel told EcoWatch in an email. “Higher lead levels in older neighborhoods are thought to be the result of lead accumulated over the period leaded gasoline was in use, from the late 1920s till the 1990s. Lead from historical leaded gasoline use has been identified as a major source of lead in other old U.S. cities including Seattle, San Francisco, and Los Angeles.”

The study, “Lead-sheathed telecom cables and historic leaded gasoline emissions substantially raise environmental lead levels in Portland, Oregon,” was published in the journal Communications Earth & Environment.

“The highest levels of lead were found in neighborhoods with old lead-sheathed telephone cables. We found lead levels up to almost 600 times the background near these lead cables. Based on reporting by The Wall Street Journal we expect similar levels of lead to be found in older neighborhoods with these lead cables across the country. The EPA has examined lead levels near these cables in New Jersey, Pennsylvania, and Louisiana. Our ongoing research includes locations in other parts of Oregon with these lead cables, including Eugene and Corvallis,” Shiel told EcoWatch.

Moss growing on urban trees can be effectively used to monitor lead levels in the air, since its wide surface area collects surrounding airborne contaminants.

“Moss and lichen growing on trees can be used as air monitors in any locations they are found. Direct measurements of lead in the soils can be used to assess the risk to residents living near these lead cables,” Shiel said.

To get a better understanding of Portland lead levels and their potential sources, the research team collected samples of a common tree moss — Orthotrichum lyelli — in the city in 2013, and from neighboring rural areas in 2017.

“These mosses are letting us know what is being picked up in the air we breathe,” said Shiel, who is also a member of the Pacific Northwest Center for Translational Environmental Health Research at OSU, in the press release.

Some older Portland neighborhoods had much higher lead concentrations than others, but the researchers weren’t sure why.

“We believe the moss in our study was contaminated with lead from the cables both by direct leaching from the cables and from lead contaminated soil landing on the moss. We think lead from these old lead cables is leached by rain into the soil below,” Shiel told EcoWatch.

Shiel said lead in the soil had the ability to move away from the location where it originated.

“Lead from the use of leaded gasoline and leached from these cables… can become airborne when soil is disturbed by wind or traffic,” Shiel said. “While the highest levels of lead are located within a meter of the cable, we see lead from these cables making it across the street.”

In the summer of 2023, the research team collected more moss samples from older neighborhoods that had telecommunications cables with lead sheaths that had been recently removed or were still in place.

The team discovered that neighborhoods where lead cables were present showed lead levels that were twice as high as those without, and in some cases 38 times higher than those in rural areas.

Shiel pointed out that additional research would be needed to find out how far the lead from the cables could be spreading. The team has plans to test the soil in these areas to find out how contaminated it is.

“We were not expecting this result. But whether or not these higher levels of lead result in people being exposed depends in part on what people are doing in those places,” Shiel said in the press release. “Right now, we are recommending people avoid interacting with or disturbing soil in those areas where these cables are or were present in the recent past.”

Shiel said people living in older residences may want to check for possible sources of lead.

“These lead cables are not limited to Portland. We know they can be found across the U.S. Residents living in older neighborhoods or in neighborhoods with older homes may want to have a look up to see if any old lead-sheathed telephone cables are present. The cables have a matte metallic appearance. They are often found attached to a support wire with cable rings although can also be wrapped to another cable or be hung without any support,” Shiel told EcoWatch.

Shiel developed a website featuring a map showing the ages of various Portland neighborhoods, along with photographs of old telecom cables, to enable residents to determine if the cables are currently in their neighborhood or have been in the past.

“Future work will focus on mapping locations with these lead cables first in Oregon and then across the country,” Shiel said.

The website provides additional information regarding potential lead contamination, as well as how to lower the risk of exposure.

“Inhalation and ingestion of lead-contaminated soil are the most likely routes of exposure. We are most concerned about children playing in soil contaminated with lead from these old lead cables,” Shiel told EcoWatch.

Shiel warned not to overlook other lead sources, such as the most common in the U.S.: household dust and soil that has been contaminated by lead-based paints.

The U.S. Centers for Disease Control and Prevention recommends testing all children at risk of lead exposure for lead poisoning. Children are especially vulnerable to exposure to the highly toxic metal, which can cause difficulty learning, developmental delays and behavioral issues.

“If residents do find lead cables they can consider having their soils tested for lead levels. If residents are concerned they have been exposed they can have their blood tested for lead,” Shiel advised. “Children are at the greatest risk for [exposure]. If you are interested in a blood lead level test or concerned you or someone in your family has been exposed, talk to your doctor or child’s pediatrician.”