In older Portland neighborhoods where lead-coated communication cables were once used, lead levels in moss are 600 times higher than in rural areas. Photo by Alyssa Seal, Oregon State University.
A new study of urban moss has found that lead levels in older neighborhoods of Portland, Oregon, where lead-coated communication cables were once used, are 600 times higher than in nearby rural areas.
Alyssa Seal, an environmental geochemist at Oregon State University and lead author of the study, said the findings highlight concerns about lead exposure in areas where lead cables were common before 1960 and where they are still installed, though no longer in use.
Lead is a highly toxic metal. Exposure to it, especially in children, can cause developmental delays, learning disabilities, and behavioral problems.
“The results were quite surprising — most of the samples with higher lead levels were in areas with old communication cables,” said Seal, an associate professor in Oregon State University’s School of Earth, Ocean and Atmospheric Sciences.
“Based on these findings, we have already begun research to understand if and how lead is entering the environment so we can know if people are being exposed to lead and, if so, to what extent.”
The study, just published in Communications Earth & Environment, was co-authored by Sarah Jovan of the U.S. Forest Service and Christina Murphy of Oregon State University.
Seale began studying lead in urban moss in Portland several years ago, after Jobin’s research ultimately traced high cadmium levels in the city to a local glass manufacturer that used cadmium-based pigments to make colored glass.
Moss growing on urban trees is an effective air monitoring system because it has a large surface area that collects pollutants that settle from the surrounding air.
“These mosses tell us what’s being put into the air we breathe,” said Seal, who is also a member of Oregon State University’s Pacific Northwest Translational Environmental Health Research Center.
In the new study, researchers aimed to better understand urban lead levels and learn more about their potential sources. Samples of Orthotrichum rieri, a species of arboreal moss, were collected across Portland in 2013 and in nearby rural areas in 2017.
The study found that lead levels were about 12 times higher in urban Portland than in nearby rural areas. Chemical analysis showed that much of the lead in the environment came from leaded gasoline, which continues to persist in the environment nearly 30 years after it was banned in the United States.
“The lead that was introduced into the environment through leaded gasoline is never going away, and we have to live with it,” Seale said.
Orthotrichum lieri, a type of moss that typically grows on trees, is an effective air monitoring system because it has a large surface area that collects pollutants that settle from the surrounding air. Photo by Alyssa Seal, Oregon State University.
But some older neighborhoods had much higher levels of lead, leaving researchers confused and searching for more answers. A Wall Street Journal study published in 2023 linking lead to communication cables in older cities prompted Seale and his colleagues to launch a new investigation.
In the summer of 2023, the researchers collected additional moss samples, this time focusing on older areas where lead-coated communication cables are still in place or have recently been removed.
“We wanted to see if the effects of lead cables were consistent throughout the areas where they are located,” Seale said.
Lead levels were found to be more than twice as high in areas with lead cables as in areas without lead cables, and 38 times higher than in samples from rural areas. The highest lead concentrations were found in samples taken within one metre of the lead cables.
The researchers speculate that lead from the cables may have been slowly leached by rain over time, accumulating in soil and plants such as moss. Contaminated soil could also become airborne, transporting lead to places other than directly under the cables.
“We know for sure that lead is migrating,” Seale said. “The moss samples show that lead is not just lurking in the soil near the cables, but that it’s migrating into the air.”
Seal said more research is needed to understand how far the lead from the cables has spread, and researchers will next conduct soil tests in these areas to determine how much lead is in the soil.
There is enough evidence of high levels to raise concerns about possible health effects, she said.
“These results were unexpected, but whether people are exposed to lead due to high levels of lead depends on what people do in those locations,” Seale noted. “We’re currently advising people not to touch or disturb soil in areas where these cables currently or recently existed.”
Seale developed a website that features maps showing the ages of different neighborhoods in the city and photos of old communication cables so residents can see if they currently have or have had these cables in their neighborhoods. The site also provides additional information about possible lead contamination and ways to reduce the risk of exposure.
Seale stressed that other sources of lead should not be overlooked: The most common source of lead poisoning in the U.S. is household dust and soil that contains lead from lead paint, she noted.
The federal Centers for Disease Control and Prevention recommends that all children at risk of lead exposure be tested for lead poisoning.
“We encourage parents to discuss lead testing with their child’s health care provider,” Seale said. “For concerned families, asking for testing would be a reasonable course of action.”
Further information: Lead-coated communication cables and historic leaded gasoline discharges5 significantly increase environmental lead levels in Portland, Oregon, Communications Earth & Environment (2024). DOI: 10.1038/s43247-024-01534-0
Courtesy of Oregon State University
Source: Urban moss study raises concerns about lead levels in older Portland neighborhoods (July 23, 2024) Retrieved July 23, 2024 from https://phys.org/news/2024-07-urban-moss-older-portland-neighborhoods.html
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