In the Lab
Research Shows Nanoparticles May Be Unlucky For Ecosystems
In a challenge to conventional wisdom, scientists have found that buckyballs, one type of nanoparticle, dissolve in water and could have a negative impact on soil bacteria. The findings raise new questions about how the nanoparticles might behave in the environment and how they should be regulated, according to a report scheduled to appear in the June 1 print issue of the American Chemical Society's peer-reviewed journal Environmental Science & Technology.
A buckyball is a soccer ball-shaped molecule made up of 60 carbon atoms. Also known as fullerenes, buckyballs have recently been touted for their potential applications in everything from drug delivery to energy transmission. Yet even as industrial-scale production of buckyballs approaches reality, little is known about how these nano-scale particles will impact the natural environment. Recent studies have shown that buckyballs in low concentrations can affect biological systems such as human skin cells, but the new study is among the earliest to assess how buckyballs might behave when they come in contact with water in nature.
Scientists have generally assumed that buckyballs will not dissolve in water, and therefore pose no imminent threat to most natural systems. "We haven't really thought of water as a vector for the movement of these types of materials," said Joseph Hughes, Ph.D., an environmental engineer at Georgia Tech and lead author of the study.
But Hughes and his collaborators at Rice University in Texas have found that buckyballs combine into unusual nano-sized clumps, which they refer to as "nano-C60", that are about 10 orders of magnitude more soluble in water than the individual carbon molecules.
In this new experiment, they exposed nano-C60 to two types of common soil bacteria and found that the particles inhibited both the growth and respiration of the bacteria at very low concentrations -- as little as 0.5 parts per million. "What we have found is that these C60 aggregates are pretty good antibacterial materials," Hughes said. "It may be possible to harness that for tremendously good applications, but it could also have impacts on ecosystem health."
Scientists simply don't know enough to accurately predict what impact buckyballs will have on the environment or in living systems, which is exactly why research of this type needs to be done in the early stages of development, Hughes said.
He suggests that his findings clearly illustrate the limitations of current guidelines for the handling and disposal of buckyballs, which are still based on the properties of bulk carbon black. "No one thinks that graphite and diamond are the same thing," Hughes said. They're both bulk carbon, but they are handled in completely different ways. The same should be true for buckyballs, according to Hughes.
These particles are designed to have unique surface chemistries, and they exhibit unusual properties because they are at the nanometer scale -- one billionth of a meter -- the range where molecular interactions and quantum effects take place. It is precisely these characteristics that make them both so potentially useful and hazardous to biological systems. "I think we should expect them to behave differently than our current materials, which have been studied based on natural bulk forms," Hughes said. "Learning that C60 behaves differently than graphite should be no surprise."
Overall, the toxicological studies that have been reported in recent years are a signal that the biological response to these materials needs to be considered. "That doesn't mean that we put a halt on nanotechnology," Hughes said. "Quite the opposite."
"As information becomes available, we have to be ready to modify these regulations and best practices for safety," he continues. "If we're doing complementary studies that help to support this line of new materials and integrate those into human safety regulations, then the industry is going to be better off and the environment is going to be better off."
The cover story of the May 2 issue of Chemical & Engineering News, the ACS weekly newsmagazine, is entitled "Nanotechnology: Ready for Wall Street?" The article describes investment and industry activities related to nanotechnology.
To view the article, visit http://pubs.acs.org/cen/coverstory/83/8318nanotech.html.
Author Envisions Grand Designs for Waste Landscape
Rubbish, refuse, garbage, scrap, waste. No matter what you call it, Americans want nothing to do with the messy leftovers of life. Take it away and forget about it.
Not so fast, says an Iowa State University landscape architect. "Waste should be brought closer to our lives and our landscapes," said Mira Engler, associate professor and author of the book, Designing America's Waste Landscapes.
Engler's book looks at the cultural and historical context of waste landscapes and considers theories and practices used by planners, designers, engineers, and others involved in waste management.
Traditionally, planners and designers have looked at waste landscapes as problems that need fixing -- nuisances that should be buried, hidden, and pushed to the margins.
That attitude inhibits creative responses to the growing problem of waste disposal, she says. Engler believes we need a pragmatic re-thinking of how we deal with garbage in this country. She challenges designers to design waste landscapes as integral, essential parts of life.
"Design and art can normalize and integrate places of waste into private, communal and public spaces in the everyday landscape. Designers need to create a space that gives something of value to the community and becomes an asset and source of pride," she said.
While researching her book, Engler traveled throughout the United States and Europe to visit landfills, recycling and waste transfer centers, and sewage treatment plants. She found examples of facilities that are innovative in concept, siting, design, or function.
"The town of Wellesley, Mass. has turned its dump into an amazing reuse, recycling park. There are drop-off stations along a circular drive for plastics, papers, tires, car oil, etc. There's a drop off for donations to Salvation Army and a library for used books. On Saturdays, it's packed with people," she said.
Engler also cites a Vancouver, B.C., sewage treatment plant that is next to a river and has been turned into a park with nature paths, a gallery, and environmental education center. In Arcata, Calif., the sewage treatment plant has been designed to be a marshland environmental center for bird watching. Other towns have turned their public waste facilities into wastewater gardens or community centers.
All are examples of how garbage can be treated in an orderly way as material and as an integral part of life.
"Whatever waste we generate ought to continue to be part of our lives and our responsibility," Engler said.
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School BUSted: Inside Air Quality Fails Test
Diesel particle pollution inside urban school buses may be worse than levels found in the surrounding roadway air, according to a study by scientists at the University of California. The report appears in the April 15 issue of the American Chemical Society's journal Environmental Science & Technology.
It has generally been assumed that other vehicles on the road are the source of elevated particle levels. But a study of school buses in the Los Angeles area shows that much of the pollution inside a school bus comes from the bus itself, and children on board may be inhaling more diesel particles than previously believed.
Diesel particles are extremely small and can deposit deep in the lungs, whereas larger particles are filtered out by the nose, mouth and throat. A number of studies have linked diesel particles to adverse health effects. For example, a large assessment of air pollution in the Los Angeles area found that diesel particles are responsible for most of the cancer risk from outdoor air pollution.
Children are especially susceptible to air pollution because they have high inhalation rates and large lung surface area per body weight, as well as narrow airways and immature immune systems, the researchers say.
They analyzed results from a UCLA school bus experiment where the researchers took out the seats and essentially turned the buses into mobile chemistry labs, driving them along actual school bus routes in the greater Los Angeles area. Six buses were involved in the study: two older high-emitting diesel buses from 1975 and 1985; two diesel buses that are more representative of current fleets; one diesel bus outfitted with a particle trap; and one bus powered by compressed natural gas.
The researchers released a tracer gas into the engine exhaust and measured concentrations of that gas inside the buses. They then calculated the "intake fraction" -- the fraction of the bus's exhaust that is inhaled by students on that bus, assuming an average population of 40 people on each bus.
The levels turned out to be substantial for all six buses, but older buses and close-windowed buses were higher, according to the researchers. The average value for intake fraction across all bus runs was 27 grams inhaled per million grams emitted, with the highest value at around 100 per million.
"This may not sound like a lot," said Julian Marshall, a doctoral candidate in the Energy and Resources Group at UC Berkeley and lead author of the study. "But intake fraction values for vehicle emissions are 5-15 per million in a typical U.S. urban area, and about 50 per million in a large urban area like Los Angeles."
The fact that these values are comparable is "shocking," according to Marshall. "This means that for every ton of pollution emitted by a school bus, the cumulative mass of pollution inhaled by the 40 or so kids on that bus is comparable to -- or in many cases larger than -- the cumulative mass inhaled by all the other people in an urban area."
The California Air Resources Board, which sponsored the original study by UCLA, recommends minimizing commute times, using the cleanest buses for the longest commutes, accelerating the retirement of older buses, and decreasing bus caravanning and idling time to reduce children's exposure to bus-related air pollutants. "Based on our work, if a policymaker wants to reduce health effects from diesel for the population as a whole, then school buses are a good source to target," Marshall said.
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This column originally appeared in the June 2005 issue of Environmental Protection, Vol. 16, No. 5.
This article originally appeared in the 06/01/2005 issue of Environmental Protection.