A new study shows asbestos fibers can move through sand and soil, a breakthrough that challenges current remediation strategies for preventing exposure to the cancer-causing mineral.
Geologist Jane Willenbring of the Scripps Institution of Oceanography at the University of California San Diego leads the ongoing study. The first phase tested the long-held belief that asbestos waste piles are locked in place when capped by soil.
Willenbring's postdoctoral researcher Sanjay Mohanty of the University of Pennsylvania discovered that when organic acids coat asbestos fibers, the threads can travel through sand and soil.
“This is something that can happen in soils, where you have organic acids that are created from plants, fungi and also bacteria,” Willenbring told Asbestos.com. “These organic acids can coat the outside of the fibers and actually change the mobility of the fibers.”
Large amounts of asbestos waste buried in the environment have concerned scientists and environmentalists for years, but surprisingly, few have explored how asbestos fibers contaminate groundwater.
“They find it in water, and they know where the asbestos is, so they can assume transport,” Willenbring explained. “But this is the first time anyone has put a known amount of asbestos in the top of a soil column and actually saw some asbestos coming out.”
Prolonged exposure to asbestos may lead to mesothelioma, a rare and incurable cancer.
Willenbring presented her findings in August at the 2016 American Chemical Society meeting in Philadelphia. The National Institute of Environmental Health Sciences funded the project.
The EPA, Superfunds and Managing Asbestos Contamination
The Environmental Protection Agency (EPA) established the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) to assess and fund the cleanup of hazardous waste sites, including those polluted with asbestos.
Areas heavily contaminated by any hazardous chemicals or other pollutants are called Superfund sites.
The National Priorities List (NPL) includes the highest priority Superfunds. There are currently 1,338 federal and general sites on the list, 13 of which are asbestos-related sites.
Willenbring and her team took soil samples from the BoRit asbestos site in Ambler, Pennsylvania. Kane Core Inc., the property's owner, dumped asbestos-containing materials from a nearby manufacturing plant at the six-acre site from the early 1900s to the late 1960s.
EPA reports show the waste pile is nearly 25-feet high. Federal officials added the site to the NPL in April 2009. Crews capped the entire site with soil in 2015.
Capping is still regarded as the safest remediation strategy for asbestos. Hauling materials away could prove more dangerous, and controlled on-site incineration is far too costly.
“Really, the EPA did the best that they could, and it's so much better than the way it was before,” Willenbring said about asbestos soil capping. “This research is to try and understand how you can do things better, which is something you always strive for.”
Understanding of Asbestos Mobility Is Still Limited
In 1977, the EPA released a report stating “asbestos migration through soil will not be a problem of any significance.”
Since then, science and research shows colloids - or a mixture in which one substance is divided into colloidal particles and dispersed throughout a second substance - move through soil, carrying other harmful contaminants with them. Despite this, the study points out the understanding of asbestos mobility remains limited.
“Colloids actually don't really settle [in water], because the small, tiny movements of the water around them keep the colloids in suspension,” Willenbring explained. “Asbestos fibers can actually behave quite a bit like colloids.”
Willenbring explained microscopic asbestos fibers and other harmful substances, such as radioactive waste, can attach themselves to colloids.
“When we started this project, we thought that surely someone would have looked at whether asbestos can move through soil,” Willenbring said. “Also, what are the controls? Not all soils are created equal. So what are the geochemical triggers that might cause asbestos fibers to be released from the soil?”
Willenbring stressed that while asbestos fibers moved through the BoRit soil samples in lab tests, it doesn't necessarily mean the fibers at the Superfund site in Ambler are mobile or that they currently exist in the area's groundwater.
“There's no evidence that it's migrating through the soil in natural conditions,” she said.
Findings of the Asbestos in Soil Study
Researchers have worked on the ongoing lab portion of the study for a couple years. It started with a sand column experiment to determine whether untreated asbestos fibers can move through sand.
Conclusion: They could not.
However, the team discovered asbestos fibers moved through the sand column when they were coated with fulvic acid, humic acid and other natural organic matter. Researchers later ran a similar test using the BoRit soil samples.
“We found that if we coated these fibers in organic acids, we could actually get the asbestos fibers to move through the soil,” Willenbring said.
She also pointed out the unique aspect ratio of asbestos fibers: More long than narrow. Because of their shape, researchers suspected asbestos fibers tangled with each other in the soil instead of moving freely through it.
What's Next for Researchers?
Willenbring and her team continue researching new directions for the study.
One idea: Figure out how to regulate the amount of organic acids in the piles to limit or decrease the amount of movement.
“We could do something else to the piles to affect their geochemistry so we don't get transport,” she said.
Willenbring said one option may involve altering the fabric used between the asbestos materials and the soil to affect the pile's geochemistry.
Another key may lie in keeping plants alive on the soil above these capped piles. Soil ecologist Brenda Casper is working with Willenbring and others to determine which native grasses best hold the top soil.
“If you don't have plants on the surface of the piles, then you have more erosion of that cap, and eventually, it will just have the same problem again,” Willenbring explained.
While grasses and native plants could prove beneficial, Willenbring said trees growing on or around the piles are problematic if they fall because their extensive root systems could unearth buried asbestos materials.
“In a place like Pennsylvania, you often have trees come in even if you don't want them,” she said. “What you basically have to do is mow the surface so the seedlings don't get a chance to take hold.”
Willenbring also pointed out that not all soils are created equal, so one remediation strategy at a site like BoRit could have different outcomes in places like Libby, Montana, the site of the largest, longest-running asbestos cleanup project in U.S. history.
“We don't yet have soil from Libby, but it would be great to get some,” Willenbring said. “Everyone is worried about Libby, and we are too.”
Willenbring used Libby as an example of how movement of asbestos fibers might not be a bad thing, in some cases. If the fibers move to groundwater, in most cases that would move them deeper and deeper into the ground, decreasing the risk of exposure.
The problem then comes when people decide to do things like irrigate, which can make a pathway between the subsurface and the surface where when the water dries out, it can lead to asbestos inhalation hazards.
“That's the kind of thing that worries us and why we're interested in finding ways to help.”
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