Johns Hopkins Issues Clarification: PVC Is NOT the Problem

A very important clarification was issued yesterday by Johns Hopkins yesterday on its study highly critical of PVC medical tubing and devices. “Just to clarify the toxin itself is not the PVC itself but the wet binding/bonding agent at the joints of PVC, cyclohexanone, ” said Artin A. Shoukas, Johns Hopkins professor of biomedical engineering and director of the University’s Center for BioEngineering Innovation and Design-CBID. “For PVC tubing in ECMO, CPB tubing, IV Bags, and Dialysis, different size tubes are joined,” Shoukas said in an email clarification to Design News.  ”(For) joining PVC tubing to acrylic connectors they use cyclohexanone as the welding/bonding agent. At every joint they use cyclohexanone.   It is the cyclohexanone that is causing issues.  We have no data on PVC alone.” The clarification is important because some other bonding system could be used to join the components, allaying concern that PVC devices are a problem. And also importantly, the study conducted by the CBID indicates other uses of the  bonding agent could require a closer look.

“For hard plastic tubing, i.e., home water supply and drainage, the bonding agent or wet welding agent has as one of its main ingredients, cyclohexanone,” added Dr. Shoukas in his email to Design News.   ”This can be bought at any Home Depot or hardware store.  Read the label.”

For more on cyclohexanone as a PVC bonding agent, see this Q&A.

The whole story dribbled out in an odd way.

Johns Hopkins Medical School issued a press release May 1 with the rather sensational headline “Chemical Found In Medical Devices Impairs Heart Function”. The lead sentence states: “Researchers at the Johns Hopkins University School of Medicine have found that a chemical commonly used in the production of such medical plastic devices as intravenous (IV) bags and catheters can impair heart function in rats.”  Right off the bat, that’s incorrect. Cycohexanone is not used in the production of these particular plastics, which were subsequently identified by Dr. Shoukas to Design News as PVC. Cyclohexanone is used in the production of another plastic.

The release also states: “The researchers thought that the cyclohexanone in the fluid samples might have leached from the plastic. Although the amount of cyclohexanone leaching from these devices varied greatly, all fluid samples contained at least some detectable level of the chemical.”

There’s no hint here that the problem actually was in the joining system, not the plastics.

The situation could have been clarified quickly if the two major trade groups representing the plastics industry had been prepared to rebut the obvious problems contained in the press release. I’m hoping to get a detailed statement soon, but this horse is already out of the barn.