Scientific American Green Chemistry
May 28, 2010 -
Features - May 28, 2010
Green Chemistry: Scientists Devise New "Benign by Design" Drugs, Paints, Pesticides and More
Chemists are usually asked to invent a solution, but without considering hazardous by-products. Green chemists now are doing both with success, but will it take regulations to enforce the approach broadly?
By Emily Laber-Warren
Back in the days when better living through chemistry was a promise, not a bitter irony, nylon stockings replaced silk, refrigerators edged out iceboxes, and Americans became increasingly dependent on man-made materials. Today nearly everything we touch—clothing, furniture, carpeting, cabinets, lightbulbs, paper, toothpaste, baby teethers, iPhones, you name it—is synthetic. The harmful side effects of industrialization—smoggy air, Superfund sites, mercury-tainted fish, and on and on—have often seemed a necessary trade-off.
But in the early 1990s a small group of scientists began to think differently. Why, they asked, do we rely on hazardous substances for so many manufacturing processes? After all, chemical reactions happen continuously in nature, thousands of them within our own bodies, without any nasty by-products. Maybe, these scientists concluded, the problem was that chemists are not trained to think about the impacts of their inventions. Perhaps chemistry was toxic simply because no one had tried to make it otherwise. They called this new philosophy "green chemistry."
Green chemists use all the tools and training of traditional chemistry, but instead of ending up with toxins that must be treated and contained after the fact, they aim to create industrial processes that avert hazard problems altogether. The catch phrase is "benign by design".
Progress without pollution may sound utterly unrealistic, but businesses are putting green chemistry into practice. Buying, storing, and disposing of hazardous chemicals is expensive, so using safer alternatives makes sense. Big corporations—Monsanto, Dow, Merck, Pfizer, DuPont—along with scrappy start-ups are already applying green chemistry techniques. There have been hundreds of innovations, from safer latex paints, household cleaning products and Saran Wrap to textiles made from cornstarch, and pesticides that work selectively, by disrupting the life cycles of troublesome insects. Investigators have also developed cleaner ways of decaffeinating coffee, dry-cleaning clothes, making Styrofoam egg cartons, and producing drugs like Advil, Zoloft and Lipitor.
Over the past 15 years, green chemistry inventions have reduced hazardous chemical use by more than 500 million kilograms. Which sounds great, until you consider that every day the U.S. produces or imports about 33.5 billion kilograms of chemicals. The annals of green chemistry are full of crazy, fascinating stories, like a plan to turn the unmarketable potatoes from Maine's annual harvest into biodegradable plastics. Still, a decade after the phrase was coined, green chemistry patents made up less than 1 percent of patents in chemical-heavy industries.
What will it take for green chemistry to be more than the proverbial drop in the bucket, a bucket full of toxic sludge? Some experts believe that the answer is government intervention—not only laws that ban harmful chemicals, but laws that simply require chemical manufacturers to reveal safety data and let the market do the rest. "Right now, companies that make chairs or cars or lipstick don't know which of the chemicals they incorporate into their products are safe," says Michael Wilson, an environmental health scientist at the University of California, Berkeley. "Once that information becomes available, there will be a demand for less toxic ingredients."
That question—to regulate or not to regulate—has split the community of green chemistry advocates. Some oppose making green chemistry mandatory: its principles are so sensible and cost-effective, they believe, that industry will implement them voluntarily. Others, such as Wilson, disagree. The key, he asserts, is "fundamental chemicals policy reform in the U.S."
Now is a critical time: After decades of inaction, the U.S. government is finally examining more aggressively the health effects of common chemicals. The ambitious Safe Chemicals Act, unveiled last month in the U.S. Senate, would require all industrial chemicals to be proved safe, creating a strong incentive for the development of less harmful alternatives. And the President's Cancer Panel released a landmark report earlier this month decrying the "grievous harm" done by cancer-causing chemicals such as bisphenol A in food and household products.
The stakes are high, higher than most people realize. The companies that make the 80,000 chemicals that circulate in our world are rarely required to do safety testing, and government agencies are relatively powerless. "This is pretty shocking, since most people assume that someone is checking what's on the market. The ingredients in my shampoo? The ingredients in my child's toys? No one's on the job? And that's the answer: By and large, no one's on the job," says Daryl Ditz, a senior policy adviser at the Center for International Environmental Law (CIEL) in Washington, D.C.
"If we're going to continue on as an industrial society that's based on synthetic chemicals, we've got to figure out a way around this stuff. There's really no question about that," says Jody Roberts, an environmental policy expert at the Chemical Heritage Foundation in Philadelphia, Pa. "I think that's where the frustration for some people is, that it needs to be happening faster."
Green chemistry's beginnings
Perhaps no one has gambled more on green chemistry than John Warner. Along with Paul Anastas, the co-founder of green chemistry and now the assistant administrator for the EPA's Office of Research and Development, he helped create a federal awards program that brought the field into the mainstream. And with Anastas he literally wrote the book: Green Chemistry: Theory and Practice, what Warner calls "a how-to guide at the molecular level." In it they establish 12 guiding principles for chemists, concepts like preventing waste by incorporating as much of the materials used into the final product, and choosing the least complicated reaction.
A dozen years ago Warner, 47, left a lucrative job at Polaroid to found the nation's first doctoral program in green chemistry. In 2007, tired of lecturing that green chemistry is the wave of the future, he decided to prove it, founding a start-up, the Warner Babcock Institute for Green Chemistry, in Wilmington, Mass. His firm, staffed by two dozen bright young scientists, is an ingenuity factory. They are working on all kinds of projects: a less energy-intensive way to make solar panels, a cheap water purification device for the developing world, and materials that mimic eye and liver tissue to substitute for live animals in toxicity testing.
Some of the work is basic research. One of Warner's core technologies is based on thymine, one of the four bases of DNA. When exposed to light, thymine molecules attach to one another; because this reaction can be harmful (think: skin cancer) many organisms possess enzymes tasked with breaking those bonds. If you put thymine in a substance and expose it to light, it hardens; apply enzymes and it softens again. No toxicity, many potential applications. A scientist in Warner's lab is using this technology to perm hair without caustic chemicals—simply by coating curled strands with a thymine-based polymer then shining light to freeze them in place. The technology could also act as a masking technique during the manufacture of printed circuit boards. Or imagine truly recyclable plastics that could be returned to their raw materials after the user throws them away.
That practical vision is a product of Warner's upbringing. He grew up in Quincy, Mass., a tough working-class town south of Boston, and he hasn't shed the local dialect. "I am a chemist. I make molecules," he says, as if he could just as easily be building a house or an engine. In his plaid shirt and scuffed sneakers, he comes across more like the kind of guy you might bring your car to when it makes a funny rattle. Warner's uncles, Sicilian immigrants, worked in construction and stone cutting, and he sees no disconnect between his blue-collar beginnings and his current gig running a 40,000-square-foot high-tech lab. "I had uncles with half fingers. I respect that—doing things with your hands, creating things," he says. "I feel that I'm working with my hands, but just in a different kind of way."
To a chemist, atoms are like so many Lego blocks to arrange and rearrange at will. Add a hydroxyl here, a phosphate there, and react with various other chemicals to get the desired color, hardness, transparency or other properties. "If we can draw a molecule, if it doesn't violate some fundamental law, we probably can make it," Warner says.
But chemistry was invented at a time when people weren't thinking about the environmental impacts. Raw materials are typically derived from fossil fuels. Turning them into the desired product can be a multistep process involving hazardous reagents (chemicals that react with the target material) and solvents (liquids or gases that provide an environment for the reaction to take place). Reactions often generate more unwanted than wanted chemicals. In making pharmaceuticals, for example, it is not uncommon to end up with 25 to 100 pounds of waste for every pound of medication.
Green chemistry starts with renewable resources such as plants or microorganisms, recycles its reagents, uses less hazardous solvents, and streamlines complicated processes. For example, in 2006 Pfizer changed the way it makes its nerve-pain drug Lyrica, substituting two plant-based enzymes for a common metallic catalyst called Raney nickel. The process now occurs at room temperature and in water, takes four instead of 10 steps, and has slashed waste and energy use by more than 80 percent.
Why so slow?
Green chemistry is elegant. It's sensible. It has the potential to improve public health and enhance the economy. But if everyone loves green chemistry—scientists, environmentalists, politicians, corporate leaders—then why hasn't it been more successful? After 15 years of innovation, the chemical industry is as toxic as ever. The politicians who lavish funding on nanotech dole out pathetically little to green chemistry. The universities that train chemists still do not require students to take a single course in toxicology. And green chemistry is far from becoming a household phrase.
To many observers, the answer is clear: What's needed is more regulation. "One way to think about it is to ask yourself: 'What is the purpose of government? Why isn't everything done by voluntary exchange among willing buyers and sellers?' The answer is, of course, that a lot of important things that need doing won't be done voluntarily," says Edward Woodhouse, a political scientist at Rensselaer Polytechnic Institute in Troy, N.Y. "It does require stick as well as carrot." Wilson and his Berkeley colleagues have acted on that principle; they helped craft the nation's first green-chemistry laws, enacted in 2008 in California. These laws require the state to identify, prioritize and take action on chemicals of concern, to encourage safer alternatives, and to make hazard information available to the state's businesses and to the public.
Warner is all for transparency, but being a chemist himself, he knows how his colleagues think, and he's concerned that if green chemistry becomes mandatory, industrial chemists will misunderstand it, writing it off as a policy-wonk proposal when in fact it is solid science, built on the core principles of traditional chemistry. Warner favors the "build a better mousetrap" philosophy: Do green chemistry by making alternatives that are not only safer but effective and economical, and chemical companies will eagerly adopt them.
But others insist that until heavyweights like Dow and ExxonMobil are forced to own up to the dangers of their chemicals, smaller companies developing clean alternatives won't be able to compete. "Some academics say, 'If we had enough students and research dollars, then wonderful new substances would flow from our labs and the world would beat a path to our door,'" CIEL's Ditz says. "But if no one can distinguish between a green molecule and a toxic molecule, it is almost impossible for safer products to break into the market."
No shift this big happens without conflict, and outrage, Woodhouse says. Average people need to know and care enough about chemical hazards to pressure business and political leaders for change. "Most people have no idea that many of the things in their houses are a danger to them," he says. "I don't think that the urgent need for a benign chemical transformation has been put out very effectively."
In addition, even when scientists come up with nontoxic, cost-saving technologies, they don't always see the light of day. The up-front expense of redesigning factories often eclipses the potential long-term savings. "Your plants are set up to run nonstop. Any downtime, even if it's going to save you a million dollars later, is costing you money now," Chemical Heritage's Roberts says.
Warner's concern is that when government gets ahead of science, the effort often backfires. "The ban will say, 'Use the best available technology.' If the best available technology is nasty, the ban becomes a license to use that technology," he says. "You can't legislate an invention, only encourage it."
The other side of the coin, however, is that sometimes when government gets ahead of science, science rushes to catch up. That happened in the mid-1990s, when the chemical company Rohm and Haas learned that a ban on tin-based marine paints was in the works. Tin-based paints had been used on ships' hulls for years because they discouraged the growth of barnacles, algae, bacteria and other unwanted hitchhikers. But tin is toxic and it was accumulating in fish, seabirds and other animals. Japan banned tin-based paints in 1992 and other nations were poised to follow suit. Rohm and Haas had never made ingredients for marine paint—and without the pending ban it would not have tried, because tin-based paint manufacturers dominated the market. But Rohm and Haas already had a mildew-fighting chemical t hat acted as a wood preservative . By adapting that active ingredient, company scientists developed Sea-Nine, a chemical that kills marine organisms by reacting with their own chemistry, breaking down into nonhazardous components in the process.
However it happens, changing worldviews takes time. It took two decades or more for global warming to gain any serious traction. Now it is seen as an opportunity to develop a whole new sector of the economy: alternative energy. The same could happen for green chemistry, as a demand for cleaner products drives innovation.
What everyone agrees on is that, ultimately, green chemistry principles must become so integrated into mainstream chemistry that the term loses its meaning. Ironically, we'll know that green chemistry has succeeded when it disappears. "The day that everyone from kindergarten students on up gets it, we don't need the field of green chemistry anymore," Warner says. "That is my goal, for it to be just the way everybody sees science."
* * *
A GREEN CHEMISTRY PRIMER
To explain the goals of green chemistry, John Warner uses the metaphor of the toolbox. Rather than wrenches, nuts and bolts, the drawers in the chemical industry's "toolbox" contain commonly used processes, such as ways to make carbon compounds or oxidation-reduction reactions. Most of these processes involve hazardous chemicals. Green chemists aim to create a new toolbox filled with less harmful alternatives, so that in the future when chemists set out to design a molecule, they'll be able to put their hands on benign tools to get the job done.
Here are some promising new technologies destined for the green-chemistry toolbox.
TAMLs: There's no pretty way to say it—TAML is short for tetra-amido macrocyclic ligand—but these apparently harmless chemicals break down a variety of stubborn pollutants, including pesticides, dyes and industrial runoff. Developed by Terrence Collins, a chemist at Carnegie Mellon University in Pittsburgh, TAMLs mimic the enzymes in our bodies that have evolved to fight off toxic assaults. Collins and his team worked for two decades to develop these smaller, easy-to-build versions of biological enzymes. When combined with hydrogen peroxide, TAMLs neutralize many contaminants by breaking their chemical bonds.
Noncovalent derivatization: A longtime passion of Warner's (his license plate reads "NCD"), noncovalent derivatization is chemistry with a light touch. Covalent bonds are the strong connections between atoms that hold molecules together. Normally, when chemists are dissatisfied with some aspect of a molecule they are creating, they alter its structure by breaking or adding covalent bonds. Such changes can involve multiple steps and hazardous ingredients. Warner's breakthrough was to posit that sometimes there's no need to create a new molecule. Simply combine the existing molecule with another substance that interacts with it, and the transient forces between them can effect the desired change. "With no energy they find each other and form," he says. "Why does a bunch of lipids fold up to form a cell membrane? Why does DNA form a double helix? It's always these weak molecular structures."
Liquid CO2: Most of us know carbon dioxide as a gas (we exhale it) or a solid (think: dry ice in fog machines). But when you put carbon dioxide under pressure, it becomes a liquid. Liquid CO2 is a benign substitute for the nasty solvents typically used to decaffeinate coffee. Just mix it with green coffee beans, then take the pressure off. The carbon dioxide evaporates, leaving behind a pile of white powder—caffeine. Do the same thing to dirty clothes and you extract oils and grime without using perchloroethylene, the notorious dry cleaning chemical.
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