Nobody Knows What Nanoparticles Do -- Yet They Are in Your Food, Cosmetics, and Toys

By Carole Bass, E Magazine. Posted July 11, 2009.

Noting that "a lot of nanoparticle uses are terrific," Lioy said he doesn't want society to do without. As scientists do the necessary studies, "I think a lot of issues will go away," he said. "I just don't want unintended consequences."

Down the Drain

Cyndee Gruden is getting the poop on nano-pollution--literally.

One of the main environmental concerns about nanomaterials is what happens when they wash out of clothing, hair or skin and go down the drain. Do they harm aquatic life? Do they interfere with wastewater treatment?

Gruden, a civil engineering professor at the University of Toledo in Ohio, is tackling part of that last question by looking at the effects of two nanometals--titanium dioxide and zinc oxide, used in sunscreens, paint and other products--on bacteria.

Metals "can be toxic to microorganisms," she notes. "In fact, that's specifically what they're for" in consumer products: to inhibit mold, mildew and other nastiness. But when nanometals make their way to a sewage treatment plant, Gruden worries that they might harm the beneficial bacteria that break down what's delicately known in the business as "biosolids."

Her preliminary findings, which she presented at a meeting of the American Chemical Society (an academic group, not an industry organization) in March, are mixed. Nano-titanium dioxide damaged bacteria, causing cell walls to break at "relatively low concentrations," similar to what you might see at a sewage treatment plant, Gruden says in an interview. But "in terms of function, what does that mean? Are the bugs able to do what they're supposed to do?"

To answer that question, she added some biosolids to her test tubes and measured how much methane the bacteria produced as they digested for five days. The titanium dioxide didn't seem to slow the bugs down; in fact, methane production actually increased. But when Gruden added nano-zinc oxide, gas production slowed down. She's running more experiments this summer to see what happens when the bacteria are exposed to the bugs for a full 30 days.

"The take-home message for me is, the behavior of these particles is very complex," Gruden says. "When you take a nanoparticle and put it into the environment, you have to know how it's going to behave. And we don't."

One metal Gruden didn't look at is nanosilver, widely used as a microbe-killer. The Project on Emerging Nanotechnologies, a nonprofit research and advocacy organization funded by the Pew Charitable Trusts in Washington, D.C., maintains an inventory of more than 800 consumer products advertised as using nanotechnology. Silver is by far the most frequently identified material.

In an experiment publicized last year, Arizona State University graduate student Troy Benn bought nanosilver-containing socks off the Internet and simulated washing them in jars of water. He found that, for several brands, most or all of the silver disappeared in just a few washings. Silver has been used to kill bacteria since ancient times, when the Greeks found that wine stayed fresh longer in vessels lined with the precious metal. It's potent enough that the U.S. Environmental Protection Agency (EPA) regulates silver as a pesticide. Which raises the question: What does nanosilver do to the "good bugs" downstream, at the sewage treatment plant and elsewhere?

In 2006, a trade organization of wastewater treatment operators was concerned enough about a new silver-ion-emitting Samsung washing machine to pressure the EPA to include such equipment under its pesticide rules. The EPA responded by cracking down, not only on the washer but also on manufacturers of products advertised to contain nanosilver, including a line of supposedly sanitary computer peripherals. Separately, a coalition of consumer, health, and environmental groups filed a petition last year asking the EPA to impose a moratorium on nanosilver products until more safety research is done. In addition, the EPA has awarded a grant to Arizona State researchers to investigate interactions between various kinds of nanomaterials and wastewater biosolids.

Oversight or Overlooked?

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Carole Bass, a journalist, writes about the environment, workplace health, legal affairs and other subjects.

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