Prof Investigates Environmental Impact of Nanoparticles

Water treatment plants can’t filter these contaminants

Prof. Brajesh Dubey

Prof. Brajesh Dubey

They’re in socks and hospital linens. They’re in plastic lunchboxes, food containers and bottles. They’re in muscle supplements and skin creams. And we don’t really know what they might do to the environment.

“They” are nanoparticles, uber-tiny bits of matter that are finding their way into a growing range of consumer products, particularly biomedical, optical and electronic components. But there’s a problem, says engineering professor Brajesh Dubey.

Referring to projected growth in their use over the next decade, he says, “Nanoparticles are being made extensively. It’s a growing market. We’re putting them into the environment and we don’t know how they will behave.”

Besides the above uses, companies are finding more applications for nanoparticles in toothpaste, soap, sunscreen, clothing, electronics, cement and paint. We need to learn more about them in order to better regulate their use and disposal, says Dubey.

Since arriving at Guelph two years ago, he’s been looking at nanoparticles as potential emerging contaminants in water and soil. Dubey says these substances end up in wastewater and, in turn, enter water bodies. Treatment plants have not been designed to handle them.

They also wind up in biosolids destined for landfill and for application on farmers’ fields. Either way, they may have largely unknown impacts on water supplies or farmland.

The Guelph engineer has looked at how size, charge and concentration of these particles affect model organisms such as E. coli and invertebrates. One paper will appear this year in the journal Science of the Total Environment.

Another paper in Environmental Science and Technology looks at the effects of organic ligands, or large molecules that end up in soil and surface water as organic matter from sources such as leaves. Dubey looked at these substances and how they affect nanoparticle stability.

His study found ligands affect silver nanoparticles, notably their surface properties. They also alter the particles’ environmental persistence and toxicity.

Nanoparticles also change depending on their precise form in the environment. Chemical effects vary when substances dissolve in solution or remain suspended in water. “Nanoparticles stay in suspension,” he says.

Our toxicity protocols will likely need to change, says Dubey, although researchers are still trying to assess the environmental impact of these substances. He expects these studies will help regulators such as Environment Canada or the United States Environmental Protection Agency develop and refine those protocols.

He has looked at how nanoparticles from biosolids used on farms may impair plant growth and development. He has also investigated how natural water chemistry affects the fate, dissolution and toxicity of nanoparticles.

His work will help improve ecological risk assessment and inform decision-making about the use and disposal of these substances, he says. Properties of nanoparticles do change in water, suggesting potential effects on ecosystem health.

He says his work tells us more about nano-chemistry in aquatic ecosystems. Referring to nanoparticles, he says, “We don’t know how they will behave in the environment. These are mostly man-made chemicals.”

Dubey arrived at Guelph in early 2012. He studied civil engineering at the Indian Institute of Technology, Kharagpur, and worked as a consulting engineer on the environmental impacts of the oil and gas industry.

He completed his PhD on the environmental effects of treated wood products at the University of Florida in 2005 and worked in the state as a research scientist for three years. After a year of teaching at the University of Auckland in New Zealand, he took a job in the public health college at East Tennessee State University.

Coming to Guelph has allowed him to shift his focus back to engineering. Recalling his introduction to the campus, he says, “I liked the friendliness, the open door policy. You can walk into anyone’s office and talk.”

He teaches courses in solid and hazardous waste management, environmental contaminants, fate mechanisms and sustainable engineering.