Producing Safer Plastics

Seeking methods to replace estrogenically active compounds.

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By Marlene Cimons, National Science Foundation

There is a lot to like about plastics.  They are lightweight and recyclable, and use very little energy to make and transport. They are affordable and convenient—and they are everywhere. But are they safe?  

Some scientists don’t think so, not yet anyway, and are working on new ways to make them safer.   

Plastics manufacturers replaced bisphenol A (BPA) following public concerns that the estrogenically active compound could leach out of baby bottles and other popular consumer items. But researchers recently released a study showing that the vast majority of BPA-free plastic products still contain other estrogenically active chemicals that also can seep out, even when new. Moreover, the ordinary stresses of dishwashing, microwaving and exposure to sunlight worsen these effects, according to the research.  

The worry is that these chemicals, still under study, potentially could be disruptive to the human endocrine system. BPA has been the focus of a number of class action lawsuits in recent years, particularly over its presence in products used by children, and the litigation is still pending. 

“While BPA is widely known by the public, most consumers do not realize that scientists suspect thousands of other chemicals may also be estrogenically active," says Mike Usey, a biomedical engineer who heads PlastiPure, one of two Austin, Tex.-based sister companies that are developing approaches to make plastic products free of all potentially hazardous chemicals. “Many BPA-free products, in fact, have higher estrogenic activity compounds than the BPA-containing products they replaced."

A team of scientists from the University of Texas at Austin, the Lombardi Comprehensive Cancer Center at Georgetown University and the two companies—PlastiPure and CertiChem—tested more than 450 BPA-free consumer products and found that, before stressing, 92 percent of them readily leached other estrogenically active (EA) compounds. Furthermore, after microwaving, dishwashing and sunlight exposure, more than 95 percent of products showed rising levels of EA. Their study was published recently online in the journal Environmental Health Perspectives.

PlastiPure, a technology company, and CertiChem, a testing laboratory, think they have the solution to making plastic products that are free of chemicals with estrogenic activity. Their research involves studying and testing substances that are used in each stage of the plastics product manufacturing process. “These encompass the full lifecycle of the product from materials to processing to certification,’’ Usey says.

The work is supported through small business grants from the National Science Foundation and the National Institute of Environmental Health Sciences.

Researchers at PlastiPure understand the molecular structures of chemical groups most likely to be estrogenic, and apply these data to each additive along the manufacturing pipeline to ensure that each one is safe. 

“For example, take a baby bottle," Usey explains. “It’s primarily polypropylene, which is safe. But when you start putting in additives to this plastic or have any residues from the catalytic chemicals used to manufacture them, any number of them could be estrogenic. We selectively sift through the tens of thousands of options, and select ones that are usable.

“We can look at the molecular structure and say: ‘that one is going to be a problem.’ Or ‘this one is a maybe.’  Or ‘that one is going to be fine,'" he adds. “The ‘maybes’ and the ‘predicted to be okay’ we definitely test in the lab. We have a large database because we’ve tested many of these materials before."

Each material introduced into the manufacturing process is scrutinized.  “Our database has many thousands of approved chemicals, and we use our models to find replacements if they’re needed," he says.  “But we can’t just send out a list of acceptable chemicals to manufacturers, since every product has different formulas and different requirements. So it’s not just making them EA-free, but making them EA-free in a commercially viable way and making sure they stay EA-free under the conditions that they’re likely to encounter over their life-cycle."