Tracking nano technology's environmental risks a tough task

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Nanoparticle research
(Left to right) Dr. Achintya Bezbaruah, grad student Sharmila Sunwar and PhD student Leelaruban Navaratnam harvest plants grown in water containing titanium dioxide nanoparticles at North Dakota State University.
Photo courtesy of North Dakota State University

Concerned about a potential environmental hazard, government regulators and researchers are studying the presence of nanoparticles in consumer products.

Nanoparticles are tiny bits of material shaped at the molecular level that can change the properties of common materials. Increasingly, manufacturers are using them to design goods that make life easier.

The antibacterial properties of silver, for example, make it a useful material to add to the fibers of some bandages and socks. But washing a pair of socks that contain nanoparticles could pose a risk to the environment.

"There's a big concern about whether these nanoparticles are going to be toxic, whether they move around in the food chain, whether humans might eventually start ingesting them in our food," said Donna Jacob, a research assistant professor of biological sciences at North Dakota State University.

Jacob, who specializes in studying wetlands and metal contaminants, is working with a team of engineers who create nanoparticles to study the potential risk.

GREAT PROMISE, GREAT RISK

Nanoparticles have great promise and great risk because the tiny particles are so much more powerful than the material they are made from, said Achintya Bezbaruah, an assistant professor of civil engineering who designs iron nanoparticles to clean polluted waters.

"A nanoparticle is 1,000 times more reactive," he said. "So even though we'll have small amount of nanoparticles, the impact may be very big."

Bezbaruah said many scientists are concerned about the potential risk of nanomaterial. That's why NDSU has put together a research team to study the entire life cycle of nanoparticles.

Bean plants
Research at North Dakota State University shows that bean plants take up nanoparticles as the plants grow. Studies now under way are examining the potential effects on plant health and plant DNA.
Photo courtesy of North Dakota State University

"As engineers we are concerned because we are taught and we teach people that we need to [understand] the life cycle from cradle to grave," he said. "We need to be sustainable."

Part of the research is happening in a small greenhouse near Jacob's office, where she is studying what happens when plants are grown in water containing nanoparticles.

She's already learned that plants absorb nanoparticles along with nutrients in the water.

As nanoparticles could kill the microbes plants need for healthy growth, or damage plant DNA, Jacob is starting a new research project to study how plants like rice and spinach are affected by nanoparticles.

There's a good chance, she said, that the effects won't be obvious.

"A lot of the times it doesn't make any visible difference, so you have to start looking deeper into the tissues to understand if there is some genetic effect that is not showing up on the surface," Jacob said. "But it might have some effect on nutrition, or it might have some effect on the next generation."

ABSENCE OF REGULATIONS MAKE STUDY DIFFICULT

Many scientists say only a few nanoparticles are being released into the environment now. But that is largely an educated guess.

There are informal efforts to track nanomaterials in products, but some scientists doubt the accuracy of those lists.

Companies are not required by law to include nanoparticles on labels, making detailed product information is hard to come by.

Bean plants grown in water with nanoparticles
Wheat and bean plants grown in water containing nanoparticles took up the nanoparticles along with nutrients in the water.
Photo courtesy of North Dakota State University

That makes assessing risk more difficult for scientists and consumers, said Steve Diamond, a Duluth-based research biologist for the federal Environmental Protection Agency.

"The more aware the public is of both the benefits and the risks of any new technology or activity in the environment the better able they are able to make their own judgment on what is an acceptable level of risk," said Diamond, who leads an EPA initiative to understand the environmental risk of nanoparticles.

But there isn't yet enough information now for consumers to make intelligent choices, he said.

Diamond said the EPA needs to know several things before it can decide how dangerous nanoparticles are, among them how common the materials are and their toxicity.

How the nanomaterials will be used also is important. Studies suggest carbon nanotubes pose environmental and human health risks. If they are used to make car tires more durable, for example, they could be released into the environment as the tires wear.

But if those same nanotubes are used in the composite material for a pair of cross country skis, it's unlikely they would ever pose a danger.

DOWN THE DRAIN, LITERALLY

The most common way for nanoparticles to enter the environment is when they're washed down the drain, Diamond said.

For example, the nano silver in socks, and the nano titanium in sunscreen or cosmetics ends up in sewage treatment plants. Diamond said it appears most of those particles are trapped in the sludge that remains after wastewater is treated.

"In that scenario, we would be more concerned about the application of sludge from wastewater treatment plants on crop lands which is a prevalent activity in the United States," he said.

In Minnesota about 46,000 tons of dried sewage sludge from wastewater treatment plants were spread on about 16,000 acres of farmland last year before farmers planted corn or soybeans. According to the Minnesota Pollution Control Agency, 91,000 tons are incinerated and 20,000 tons are put in landfills.

There's no easy way to test that sludge for nanoparticles.

MEASURING IMPACT

With nanoparticle production and use in products expected to grow rapidly in the next decade, scientists hope to better understand the risk of their use before they become ubiquitous in the environment.

Still, nanomaterials are not likely to cause immediate dramatic environmental damage, said Christine Hendren, executive director of the Center for Environmental Implications of Nanotechnology at Duke University.

Whatever happens will likely be subtle and long term, she said, which makes it much more difficult to assess risk.

A big question for consumers is whether they should be concerned.

"Only the public can express public demand for information that will help keep them safe."

"It would be similar to saying, 'should we be worried about chemicals?' Sure, some of them," Hendren said. "We don't know much about most of the chemicals that are in the environment."

Scientists are just starting to learn about the risk posed by some chemicals that have been in the environment for decades.

Based on past experience with chemicals, Hendren said, it might be time to develop a new way to assess environmental risk. She thinks there's still a chance to get ahead of any danger posed by nanoparticles.

"I think that nanomaterials offer us a really great chance to consider whether as a society we might want to act in a more precautionary manner," she said, "and not let markets drive the release of materials as much as our intelligent, intentionally weighed values of whether we want to take some risks and what benefits this offers."

Hendren said as a scientist and a consumer, what she most needs is information: How much nanomaterial is being produced? Who's using it? Where is it going?

But that information is not available because nanotechnology is not regulated.

"The market drives the economy in North America," she said. "And I think public involvement and public demand of information is a really valuable tool. Only the public can express public demand for information that will help keep them safe."

Hendren said regulation and labeling of nanomaterial will be even more important as nanotechnology expands to more products, and scientists try to understand the potential risk.

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