In Business, Creating Sustainable Enterprises & Communities

THE PROMISE OF NANOTECHNOLOGY

In Business, July-August, Vol. 29, No. 4, p. 18

Breakthrough technology may impact almost every sector of the economy, but critics raise concerns about human health and environmental risks.

Diane Greer

POLYLACTIC ACID and other biobased plastics offer a sustainable alternative to conventional petroleum-derived plastics. But performance limitations have hindered widespread adoption.
Now a new technology employing the tiniest of particles is improving performance characteristics of bioplastics. TDA Research in Golden, Colorado, illustrates the promise of nanotechnology. The company is developing a bioplastic, composed of polylactic acid (PLA) and microscopic boehmite particles, to create food packaging with improved thermal, strength and barrier qualities.
Beyond bioplastics, nanotechnology is producing cheaper solar cells, novel cancer drugs, lighter building materials and faster electronic devices. Over 500 consumer products already use nanotechnology including cosmetics, personal care products, clothing and food. Lux Research estimates $2.6 trillion of manufactured goods will incorporate nanotechnology by 2014.
This breakthrough technology is expected to impact almost every sector of the economy. Many believe it will drive the next industrial revolution. But amid all the fanfare, there are voices raising concerns about potential human health and environmental risks associated with nanotechnology.

WHAT IS NANOTECHNOLOGY?
Nanotechnology is the science of manipulating matter at the atomic and molecular level. Its potential power lies in the unique properties displayed by common materials at very small sizes, less than 100 nanometers (a human hair is 80,000 nanometers wide).
“At that small scale, the properties of materials change and engineering can now allow us to take advantage of these properties,” says Jennifer Sass, senior scientist with Natural Resources Defense Council (NRDC) in Washington, D.C. At nanoscales, materials may be stronger, conduct electricity or display magnetic or optical properties not seen in the same materials in bulk form. Nanotechnology seeks to exploit these new properties to produce new materials, products and devices.
NASA funded TDA's initial work with nanocomposite bioplastics as part of a project to develop biodegradable food packaging for space. Packaging to preserve food on long-term space flights has very specific performance requirements and must biodegrade in on-board compost units, explains Andrew Meyer, senior chemist at TDA. For the NASA application, TDA employed a naturally occurring aluminum oxide-based mineral called boehmite. “It is a commodity material that is a ceramic precursor,” Meyer adds. Particles are platelet shaped and measure 40 by 40 nanometers by about 2 nanometers thick.
Separating the bulk material into nanoscale particles and dispersing them within the polymer proved challenging. “Usually nanoparticles are like tiny rocks,” says Meyer. “They are not designed to dissolve in anything.” To facilitate dispersion, TDA chemically modified the particle's surface area. Once dispersed in the polymer, the nanoscale particles are below the wavelength of scatter light, making them appear transparent. The resulting nanocomposite bioplastic exhibited improved water vapor and oxygen barrier properties and also addressed thermal stability and strength. Desired property improvements were achieved by adding nanoscale boehmite to PLA at very low concentrations, about one percent to five percent by weight.
At the U.S. Army Natick Soldier Center (Natick) in Massachusetts, researchers explored the use of a nanoclay with PLA to create packaging for MREs (Meals Ready to Eat). Army packaging requirements call for a three-year shelf life and temperature stability at 80°F, explains Jo Ann Ratto, research engineer at Natick.
Efforts were unsuccessful producing a biodegradable nanocomposite to meet these stringent requirements. But investigations are continuing for the Navy with another bioplastic, polyhydroxyalkanaotes (PHA). “PHA biodegrades readily in a marine environment, and the Navy does not have as stringent food packaging requirements as the Army,” Ratto says.
Cereplast was one of the first companies to use nanomaterials in bioplastics. The goal was to produce a resin with the same physical and thermal qualities as traditional petroleum-based plastics, explains Cereplast president and CEO Frederic Scheer. The materials most commonly used in the company's nanocomposite bioplastics are nanoclays, which range from 300 to 500 nanometers in diameter and vary in concentrations from 0.1 percent to 3.5 percent by weight.
“The introduction of nanomaterials has allowed us to improve strength, stability and heat resistance as well as substantially improve barrier qualities up to 70 percent,” says Scheer. Improving barrier qualities is critical for packaging applications designed for transporting fruits and vegetables. Since standard bioplastics permit the passage of oxygen, any gases injected into the packages to keep the contents fresh quickly leak from the packaging.
Other researchers also see the promise of nanocomposite bioplastics. At Michigan State University, professor Ramani Narayan recently patented his work incorporating nanoclays in starch blends. “We have shown some very market increases in performance qualities with tensile strength,” Narayan says.
Assistant professor David Grewell at Iowa State University is working on techniques to improve separation and dispersion of nanoclays in bioplastics using high-frequency sound waves. Meanwhile, at the State University of New York, Professor William Winter is strengthening plastic with cellulose nanocrystals derived from wood.

SIZE MATTERS
While the potential power of nanotechnology lies in its small scale, so do the risks. “If you have something which behaves in different ways, there are going to be new and possibly unique risks associated with it,” says Andrew Maynard, chief science advisor with the Project on Emerging Nanotechnologies (PEN) in Washington, D.C. NRDC scientist Sass agrees: “With nanomaterials, some of the properties that make them so advantageous are some of the same properties that we need to think about in terms of new toxicities and new potential harms.”
While different properties don't necessarily imply that nanomaterials are hazardous, it does mean that the health and safety consequences of nanomaterials cannot be assessed based on knowledge of the larger-scale substances. “What's lacking is the linkage between that unusual behavior and how that might affect someone's health,” Maynard declares. “This is where we need to do a lot more research.”
Research suggests there is cause for concern. Because of their small size, nanomaterials can be easily inhaled, ingested or absorbed through the skin. Studies on animals indicate that when very fine particles are inhaled, they can penetrate through to the blood and impact the cardiovascular system and other organs in the body, Maynard says.
Other research has shown nano-sized particles deposited in the nasal region can move up the olfactory nerve to the brain, circumventing the blood brain-barrier. “This is something large particles can't do,” he adds. Their tiny size enables some nanomaterials to enter living cells. For example, under laboratory conditions, some nanomaterials have been shown to bind to and mutate DNA. “You can't extrapolate these results across all nanomaterials except to say that the things that excite us about nanomaterials are the same things that should make us pause and make sure we do our homework first,” Sass says.
Research is also required to examine the potential toxicity of nanomaterials in the environment. Nanoparticles could be emitted into the air or discharged into waste streams during manufacturing processes. Releases might also occur when nano-based products undergo decomposition after disposal. Nanosilver, primarily used as an antimicrobial and to eliminate odors, exemplifies the potential problems. It is already found in 95 consumer products including food packaging, personal care products and apparel.
“Nanosilver is very reactive and known to be highly toxic to aquatic organisms,” Sass explains. During normal use or decomposition after disposal, nanosilver may find its ways into waste streams where it could kill beneficial bacteria, such as those integral to the food web in streams or used to treat wastewater.

TESTING NANOMATERIALS IN BIOPLASTICS
Manufacturers and food packaging producers are aware of the potential risks of nanotechnology, says Michael Holman, senior analyst at Lux Research in New York. “There are also concerns among food packaging producers and users that nanotechnology might be seen by consumers as something that is risky.”
Adds TDA's Meyer: “There is certainly a huge concern about the environment, the effects of nanoparticles on people using them in the lab and in formulations downstream and their eventual fate.” “We are trying to design the nanoparticles to be as green as they can be.” He does not anticipate any big barriers to putting the nanomaterials TDA is developing in composting environments but said testing would be done.
Richard Farrell at the University of Saskatchewan, Saskatoon, performed preliminary soil toxicity testing for the Army's Natick team. Soil containing decomposed nanocomposite bioplastics was used in seed germination and plant seedling tests based on U.S. Department of Agriculture and Compost Council standards. “There was no toxic affect at all,” says Farrell. The next step is to create a compost pile composed of 25 to 30 percent nanocomposite bioplastics to see what effect the materials may have on the compost quality.
In many cases, there are no established tests specific to nanomaterials. Producers don't have any clear guidance on what should be done to insure a product's safety before putting it on the market, Maynard continues.
Cereplast's experience provides some insight into the issues facing companies trying to test nano-based products. First, the company wanted to understand the Food and Drug Administration's (FDA) position on the use of nanomaterials in plastic materials used in food packaging, its primary market, Scheer explains. “FDA's concern is for nanomaterials that are below 250 nanometers,” he says. Cereplast's nanoclays are sized from 300-500 nanometers. “Secondly if we create a product that is being used to package food, we want to make sure that we don't have any form of leakage of the nanomaterials outside the package.”
Cereplast's law firm worked with the FDA to design special migration protocols to test for leakage. Subsequent migration tests of the products by an independent lab verified that there was no leakage.
The Biodegradable Products Institute (BPI), which developed standards for certifying plastic products biodegrade completely and safely in commercial composting facilities, also tested the product to determine if nanomaterials affected biodegradability or compostability. “There was no effect,” Scheer says.
He does not believe nanomaterials in Cereplast resins will affect compost quality: “All the nanoclays we use are natural and are probably already present in very large quantities in the soils.” Very low concentration of nanomaterials, between 0.1 percent and 3.5 percent, also makes it next to impossible to accumulate any discernable amount of the materials in compost, he adds.

SHOULD WE BE CONCERNED?
Should consumers and composters be concerned about nanocomposite bioplastics and nanoproducts in general? “If you are using a new and innovative technology, the first step is to ask critical questions,” Maynard says. “Chances are that many of these applications are going to be harmless and the benefits will far outweigh any risks. But we cannot rest on that assumption.”
Michigan State University Professor Narayan argues that particles measuring 300 to 500 nanometers should not be classified as nanomaterials, commonly defined as less than 100 nanometers. “What people are calling nano is not truly nano,” he says. Narayan, who heads the BPI's Scientific Review Committee, believes this distinction is important because potential risks associated with nanoparticles are not an issue with larger sized particles. When bioplastics are available that contain materials at true nanoscales, then the concerns are genuine, Narayan says. “The fact that ASTM (American Society of Testing and Materials) has two committees currently looking into nanomaterials reflects that concern.”
The ASTM committees are establishing standards addressing the physical, chemical and toxicological properties of nanomaterials and environmental, health and safety issues. Narayan expects the appropriate nanotechnology standards to be integrated into the BPI specifications once they are completed. Issues related to particle size, behavior and concentration are not always black and white, Maynard cautions, adding: “Particles between 250 to 500 nanometers are probably too large to cross the blood-brain barrier. However, particle shape and chemistry also play a role.”
Another consideration is whether specific types of nanomaterials can accumulate in the environment at harmful levels. “Before naively assuming naturally occurring and processed materials are the same, we need to ask critical questions about whether any modifications, which may change particle shape, size, chemistry, etc., will affect the material's potential to cause harm,” Maynard notes.
Precautionary regulations are needed, Sass says. Since preliminary data indicate the potential for toxicity, unsafe or untested nanomaterials should not be used in ways that might result in human exposures or environmental releases. She also argues for full lifecycle testing to assess potential problems and public participation in the decision making process.
“First and foremost, we must have a solid strategic research program,” Maynard says. “Decisions have got to be based on good science and not speculation. Secondly, we need to find a way to make good decisions based on limited information, without being swayed by speculative thought.” Information must also be communicated to the general public so they can make informed decisions.

FUTURE OF NANOCOMPOSITE BIOPLASTICS
While nanotechnology is proving to be technically successful at improving material properties, costs are still an issue. Nanomaterial costs as well as processing costs to separate and effectively disperse nanomaterials within bioplastics are high enough that the value proposition in using them has just not been there, Holman of Lux Research says.
Scheer believes that he can produce nano-based resins that are price competitive. But prices for the final bioplastic products will still be higher due to inefficiencies in running biobased resins on processing equipment designed for petroleum-based resins, he adds. “They are just starting to design special equipment for biodegradable resins.” He also points to issues with distribution and demand contributing to higher prices for biodegradable products.
For Maynard, the issue with commercializing nanocomposite bioplastics and other nanomaterials is doing the right science to ensure we are on the right track to make these technologies as safe as they can be. “Composite materials with nanoparticles and nanoclays could be a tremendously beneficial technology,” Maynard says. “It would be a real shame if that work were killed because we do not do the background research necessary to demonstrate their safety.”
Meanwhile work is continuing in laboratories to develop true nanoscale bioplastics. Both Meyer and Narayan believe it will take another five years before products hit the market.

Sidebar:

NANOTECHNOLOGY RESOURCES

EPA & Nanotechnology: Oversight for the 21st Century - Report from the Project on Emerging Nanotechnology - (http://www.nanotechproject.org/file_download/197)

EPA Nanotechnology White Paper - (http://www.epa.gov/osa/nanotech.htm)

Foresight Nanotechnology Institute - (http://www.foresight.org)

Green Nanotechnology: It is Easier Than You Think - Report from the Project on Emerging Nanotechnology - (http://www.nanotechproject.org/file_download/187)

Nanotechnology: Small Science Big Consequences - NRDC report (http://www.nrdc. org/health/science/nano/contents.asp)

National Nanotech Initiative - (http://www.nano.gov)

Nanowerk Nanotechnology Portal - excellent information source on nanotechnology (http://www.nanowerk.com/)

Project on Emerging Nanotechnologies - Established in April 2005 as a partnership between the Woodrow Wilson Center for Scholars and the Pew Charitable Trusts (http://www.nanotechproject.org)