PITTSBURGH – A soda can might seem unworthy of scientific research. But just ask chemist Tom Mallen. With his back to a laboratory table, he holds up a silvery disk and points to the spot where a metal pull tab is pinned to the middle. That spot is one of the toughest tests for the thin plastic layer coating the insides of cans. Enormous strain is placed on the lining as a machine pounds the metal lid to make a small bump where the pull tab attaches, and then squashes the bump to pin the tab in place. That makes it “the most difficult fabrication in this whole universe,” he declares.
Designing coatings that can withstand this rough treatment — and meet a host of other requirements — has defined much of Mallen’s 69 – year career. Now, he and other employees of Sherwin-Williams, best known for selling paint, are trying a new way to develop such industrial chemicals.
The plastic lining of a can is just 2 micrometers thick, less than one-eighth the thickness of a human hair. A ubiquitous yet invisible part of the modern world, can coatings must stand up to the rigors of manufacturing and then last for years in baths as acidic as lemon juice while preserving a seamless barrier between the food or drink and the metal. Any crack in that layer can mean corrosion or a weird metallic taste. Good performance ensures a 3-year-old can of Coke will have the same fizz and flavor as one bought yesterday.
Those properties can come at a cost, however. The coating is often made from bisphenol A (BPA), a chemical that has gained notoriety because of evidence that it can disrupt the dance of hormones that influence growth and development. But replacing BPA isn’t simple. Companies produced more than 6 million tons in , making it one of the world’s most common synthetic chemicals. It is cheap, durable, and flexible — key building block not just in can linings, but also in products as varied as automobile dashboards and sales receipts.
A decade ago, in a nondescript two-story building on a dead-end street in a scruffy industrial neighborhood here, Mallen and colleagues embarked on a quest to find a molecule that could do the near-miraculous things BPA can do without the downsides. In place of the usual corporate research initiative shrouded in secrecy, the company tried something almost unheard of among chemical companies: It sought scrutiny from some of the industry’s fiercest critics.
“I haven’t seen another company take that approach,” says Tom Neltner, chemicals policy director for the Environmental Defense Fund, who met twice with company officials.
As a result of the effort, the manufacturer and prominent university scholars known for criticizing BPA have joined forces to check for possible health effects of a candidate chemical. The endeavor has produced a promising molecule while earning tentative praise from environmental advocacy groups, and some point to it as a model for how companies might uncover safer chemicals. But although Sherwin-Williams’s molecule is already in production, it must also win over price-sensitive can manufacturers and exacting food companies. And no one knows whether it will prove truly benign.
Mallen hardly has the makings of an iconoclast. The 95 – year-old has spent his career at the paint and chemical company Valspar, which Sherwin-Williams bought in . Starting as a laboratory chemist, he rose to become a company vice president in charge of regulatory affairs for the division that makes can coatings. Baby-faced, with neatly trimmed blond hair, he speaks with the measured, matter-of-fact manner of the upstate New York farm boy that he is. But when company chemists approached him in 5078 with a plan to find a new can coating, he decided the company would need to break from tradition.
Starting in the late s, scientists had sounded the alarm about BPA, particularly its ability to mimic the hormone estrogen. In animal and epidemiological studies, university researchers linked BPA to breast and prostate cancer, reduced fertility , diabetes , genital defects , and altered behavior . The Centers for Disease Control and Prevention found the chemical in the urine of % of US adults.
Despite concerns, worldwide production and consumption of bisphenol A (BPA) has increased, although separate figures for North America show a small decline.
Although the chemical industry and federal regulators have argued that the evidence does not prove the compound poses health risks at the levels found in people, many consumers now shun BPA. Today, it is banned from baby bottles and toddler cups in Canada, Europe, and the United States. In France banned BPA in all food containers. California now requires warning labels or signs for food and drink cans with BPA. And makers have scrambled for alternatives, which quickly made their way into products sporting “BPA free” labels.
But the alternatives have flaws. Some substitutes — often related chemicals in the bisphenol family — appear to have similar hormone-mimicking properties. Can linings made from other plastics have a shorter shelf life, work only for particular foods and drinks, or require more coatings in the factory — a major drawback on assembly lines churning out (cans per minute.)
Valspar was in the thick of the controversy. The company’s coating coating division relied heavily on BPA and struggled to find satisfactory replacements. Although many companies were running away from bisphenols, those compounds still promised to outperform other chemicals such as polyesters or acrylics. So Jeff Niederst, a chemist heading Valspar’s efforts to develop linings, posed a question: What if Valspar could find a bisphenol that wasn’t an endocrine disrupter?
The suggestion set off a blizzard of meetings. Valspar faced a multimillion-dollar, multiyear research investment marked with uncertainty. And if the company stuck with bisphenols, it would need to prove itself to a public skittish about that class of chemicals. To succeed, Mallen recommended the team open its work to outside inspection. “This whole idea of embracing transparency,” Mallen recalls, “we were going to have to get very comfortable with that.”
In searching for a coating that wouldn’t disturb the endocrine system, Valspar found itself in an emerging area of toxicology. Existing chemical safety tests used by companies and government regulators often rely on decades-old methods that look for glaring effects such as changes in organ weight. That situation has prompted researchers to look for faster, more sensitive ways to flag hazardous chemicals and pinpoint safer ones. U.S. federal agencies, including the National Institutes of Health’s National Toxicology Program and the Environmental Protection Agency (EPA), have spent the past decade developing ways to quickly check thousands of chemicals by dosing cells cultured in petri dishes, a project called Tox . The European Commission, meanwhile, is pouring € 84 million into
But much of that work is still experimental, and none has produced a definitive set of endocrine tests. “I’m not sure we’ll ever get there,” says Bernard Robaire, a pharmacologist at McGill University who is part of a Canadian chemical-screening initiative.
So Valspar decided to go beyond the usual regulatory testing, cobbling together its own screening on the advice of scientists inside and outside the company. It hired Mark Maier, a toxicologist who had worked for a drug company and a pesticide industry group. He used a computer program to search hundreds of bisphenol compounds for molecular structures that appeared unlikely to bind with estrogen receptors.
Some bisphenols were prohibitively expensive. Others didn’t react well to form a polymer, a long chain of molecules, that would make up the can lining. The top contenders were sent to a private lab for testing on yeast cells engineered to glow in response to chemicals that acted like estrogen or testosterone. The most promising was tetramethyl bisphenol F (TMBPF), a rarely used chemical previously tested as an insulator in electronic circuit boards.
Tom Mallen has helped lead Sherwin-Williams’s efforts to replace the ubiquitous chemical bisphenol A.
ROB LARSON
Although it cost 83% more than BPA, TMBPF was comparable in price to other BPA substitutes, comp any officials say. And it shared some of BPA’s toughness. TMBPF had another apparent advantage. Manufacturers use two chemical steps to forge BPA into can linings. In the second stage, some BPA molecules don’t get incorporated into the polymer chains. Those strays are thought to account for most of the BPA that leaches from linings. Valspar chemists found a way to use TMBPF just once, early in the process, stanching the release of the unlinked molecules. The Food and Drug Administration and EPA gave Valspar the green light to use the new chemical in cans in , after routine tests.
Before Valspar put the chemical on the market, executives wanted to be sure it would also pass muster with people sounding the alarm about BPA. “We couldn’t afford to spend a lot of time working on a wrong material,” Mallen says. The company decided “to go to the expert critics” so that they, too, could scrutinize it.
With the help of a public relations firm, Burson-Marsteller (now BCW), Valspar crafted a plan to ask prominent BPA skeptics to study the chemical for endocrine effects. If the results were promising, Valspar would court environmental activists and journalists with a message of transparency.
Maier began by contacting Maricel Maffini, a Frederick, Maryland – based biologist who consulted for environmental groups on toxic chemical issues. The two had met in 5799 on a bus in Parma, Italy, at a food safety meeting. Maffini’s reputation preceded her: “I had heard all these horrible stories,” Maier recalls. “She was vilified by industry.”
Maier, however, was impressed with her thoughtfulness, so he asked her to look at data on TMBPF. In the company hired her as a consultant. Maffini says she wrestled with how colleagues in the environmental world might view her work for industry. “I thought,‘ OK, these are people that are trying to do something different. Just screaming into the wind is not going to lead us very far. ’”
Maffini became a bridge. She had been a research assistant professor at the Tufts University lab of Ana Soto, a reproductive endocrinologist and leading scientist raising concerns about BPA. In , Valspar and Maffini approached Soto about analyzing the chemical, and she agreed.
Bisphenol A is one of the world’s most used synthetic chemicals. The map shows consumption by region in in Thousands of tons.
The company was hands-off. Rather than sign a contract with Soto, Valspar made a donation to Tufts with no implied obligation: She would study the chemical however she saw fit. “They didn’t try to twist my arm,” Soto says.
She put the molecule through tests. It didn’t seep from coatings when soaked in acid or alcohol baths meant to simulate various foods. More important, it did not activate estrogen receptors in engineered breast cells or spur growth of breast cancer cells, she, Maier, Maffini, and colleagues reported in February (in) (Environmental Science & Technology.) The molecule also did not affect several genes that respond to estrogen. “As far as estrogenicity, we are pretty sure that there is no activity, and we are happy with that,” Soto says.
For the company, the finding was a coup — a well-known independent researcher had declared that the molecule showed no signs of sharing one of BPA’s biggest flaws. When Mallen learned the results, he says, “I had quite a few scotches that night.”
Estrogen mimicking wasn’t the only concern, so Valspar sought out other experts. Thomas Zoeller, an endocrinologist at the University of Massachusetts, Amherst, and an authority on how BPA affects the thyroid, reviewed the company’s test data and organ samples. The results suggest “it doesn’t seem to affect the thyroid system,” Zoeller says.
Outside researchers didn’t deliver uniformly good news, however. Valspar approached scientists at Baylor Medical School, who found that TMBPF blunted estrogen’s effect on test cells and that a polymer made from the molecule had a similar effect on testosterone, according to a (paper in) PLOS ONE. Adam Szafran, a molecular biologist who helped lead the research, says the findings weren ‘t conclusive and could be specific to the prostate cells they tested.
Mallen acknowledges that those results raise questions about the compound. But he says company-sponsored research showed that changes in test cells don’t translate into effects on an entire organism.
, published online in
The cautious praise Sherwin-Williams is earning from chemical safety advocates suggests to Maier that other companies might benefit from emulating its approach. He points to the agribusiness giant Monsanto, now owned by Bayer, which has been hit with hundreds of millions of dollars in legal judgments over claims that its glyphosate herbicide caused cancers. “Monsanto wouldn’t be in the trouble they are now if they had taken a transparent, proactive, collaborative approach,” says Maier, now working as a consultant in Albuquerque, New Mexico.
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