Research breakthrough could cleanse soil, sediment and water pollution
New research from Michigan State University has shown for the first time that activated carbon can help eliminate the health risks associated with soils, sediments and surface water polluted by highly toxic dioxins.
EAST LANSING, Mich. – New research from Michigan State University (MSU) has shown for the first time that activated carbon – a substance widely used in water purification – can help eliminate the health risks associated with soils, sediments and surface water polluted by highly toxic dioxins.
Stephen Boyd, a University Distinguished Professor in the MSU Department of Plant, Soil and Microbial Sciences, led the study, which is published online in the journal Environmental Toxicology and Chemistry. The research looked specifically at soil and freshwater ecosystems that had been contaminated mainly through the industrial manufacture of pesticides and other chemicals.
“The goal is to find and validate a new direction in the management and remediation of soils and sediments that are contaminated with industrial pollutants, like dioxin,” said Boyd. “We were finally able to achieve that goal with activated carbon. Our work showed that using it rendered dioxin completely unavailable to the food chain.”
Activated carbon is produced when materials with high carbon concentrations, such as coal, wood, peat or even coconut shell, undergo special treatment processes that expose them to extremely high temperatures without burning them. The result is a porous, highly adsorptive substance that binds easily with organic toxins. When mixed into contaminated soil or sediment, the activated carbon draws dioxin to it and sequesters it.
Though the release of dioxins into the environment has been reduced by over 90 percent since 1990, the toxins already released continue to persist in the environment, and can enter the food chain through fish and other organisms.
“There’s a general malaise of health issues associated with dioxin contamination,” Brett Sallach, postdoctoral research associate in the MSU Department of Plant, Soil and Microbial Sciences who worked on the project, said. “Hormone health complications, fertility issues, skin rashes, immunity problems, cancer: they all can stem from it. Most human exposure is linked to eating fish and shellfish that live in contaminated streams and riverbeds.”
Removing dioxin from contaminated soil and sediment currently requires expensive, years-long dredging of river beds, followed by disposal in hazardous waste landfills. While activated carbon’s capacity for sequestering toxins is well documented, there were questions whether those toxins remained a danger to animal, and ultimately human, health.
Boyd and his team received a five-year, $2 million grant from the National Institute of Environmental Health Sciences Superfund Research Program to do the research.
They conducted a series of three experiments to determine whether activated carbon effectively reduced the entry of dioxin into the food chain. The team mixed the most toxic form of dioxin (tetrachlorodibenzo para dioxin) with silica, Bentonite (a clay used to line landfills) and activated carbon, exposing mice to each of the mixtures.
In the first two experiments, the samples showed no ability to reduce dioxin availability, as the toxin readily appeared in the systems of the exposed mice. However, when mice were exposed to the third sample, containing activated carbon, they showed no signs of dioxin toxicity. The team had demonstrated that adding activated carbon to dioxin-contaminated soil or sediment would protect a mammalian organism from its harmful effects, a key step toward demonstrating the mixture would protect human health.
Activated carbon, estimated to cost approximately $75,000 per hectare, would be significantly cheaper than conventional dredging and landfilling methods, which are estimated at $15 million for an equivalent operation. Boyd said that activated carbon represents a less disruptive, more cost-effective approach to ecosystem remediation, although some heavily polluted sites might still require dredging.
Boyd said further testing is necessary, but he adds that the findings represent an important step forward in environmental restoration technology.
“Our study is significant because it provides the first direct evidence that this technology would ultimately be protective of human health,” Boyd said. “The idea that we have assisted in the development of a technology that is effective and less expensive than current methods is very satisfying, and it stands to help a lot of people in the future.”