Features

Polycarbonate (PC) is one of the engineering thermoplastic materials most commonly used and most widely tested in the medical device industry today. Its inherent strength, excellent optical clarity, high heat distortion temperature, and dimensional stability make it an ideal material choice for demanding, critical healthcare applications.

Fig. 1 – Polycarbonate avoids breakage that can create an unsafe environment in a wide variety of items such as tubes and connectors.
Polycarbonate has been used safely in this industry for decades. It meets the industry’s requirements for maintaining the highest levels of quality, purity, and consistency to protect the lives and health of patients. Depending on the end use proposed for devices, certain tests need to be performed on the resin to ensure biocompatibility with living sys tems, retention of end-product physical properties, and optical clarity. PC can meet these rigorous regulatory and compliance standards.

Despite the obvious advantages of polycarbonate, the safety of the material has been a constant source of controversy because of the presence of bisphenol A (BPA). BPA is a monomer used in the polymerization of PC and is a necessary ingredient and an integral part of the plastic that allows the material to deliver a variety of unique benefits.

BPA is present in polycarbonate after polymerization at very low residual levels. The concern has always been related to the level of BPA residuals that might migrate from the plastic, and whether or not there are health and safety issues associated with very small levels of BPA.

Polycarbonate Safety & BPA Earlier this year, Styron, Berwyn, PA, hosted a webinar called “Polycarbonate Safety in Medical Applications: Bis phenol A & Recent Findings,” (http://www.ides.com/webinars/2013/polycarbonatesafety-medical-applications.asp). One of Styron’s goals in sponsoring the webinar was to educate customers, distributors, and industry colleagues about the science. Those who work with polycarbonate materials every day are confident in their science and safety, but also recognize the challenge of sifting through information available in the market.

The webinar featured a leading medical device company, Ethicon Surgical Care, as well as Dr. Steve Hentges, executive director of the BPA Global Group at the American Chemistry Council. Ethicon shared analytical research performed by the company that addresses the safety of polycarbonate as a material for medical devices. Hentges presented the science surrounding the safety of polycarbonate and BPA.

Essentially, BPA is one of the most thoroughly tested chemicals used today. Numerous expert panels and government agencies have declared BPA to be safe for use in many applications. While many of the reviews and conclusions regarding BPA have been focused on food contact applications, the underlying science that supports these conclusions is applicable to medical devices as well.

Government and scientific bodies around the globe have extensively evaluated the weight of scientific evidence of bisphenol A and have declared that BPA is safe as used, including in materials that come in contact with food (American Chemistry Council, 2013, http://plastics.americanchemistry.com/Product-Groups-and-Stats/PolycarbonateBPAGlobal-Group).

“FDA’s current assessment is that BPA is safe at the very low levels that occur in some foods. This assessment is based on review by FDA scientists of hundreds of studies including the latest findings from new studies initiated by the agency.” (FDA, 2013)

In September 2011, an international panel of experts organized by the World Health Organization and the Food and Agriculture Organization of the United Nations released a report on their review of all the latest scientific evidence on BPA and concluded that “initiation of public health measures would be premature.” The experts also concluded that BPA does not accumulate in the body, is rapidly eliminated in urine, and that it is difficult to interpret the relevance of studies claiming adverse health effects from BPA.

Studies show that a consumer would have to ingest more than 1,300 pounds of food and beverages that were in contact with polycarbonate plastic each day to reach the BPA “safe exposure level” established by government bodies in the United States and Europe. Extensive data from biomonitoring studies conducted by the U.S. Centers for Disease Control and Prevention (CDC) show that typical human exposure to BPA from all sources is approximately 1,000 times below the safe intake level recently set by the European Food Safety Authority.

In addition, numerous scientific studies show that the very small amount of BPA that may be ingested by a person during normal daily activity is efficiently converted to biologically inactive meta - bolites which are eliminated from the human body within 24 hours. It doesn’t remain in the body and it doesn’t accumulate in the body.

Even with all of these scientific findings, there continues to be significant opposition to BPA and concerns about its safety. There are a wide range of applications and markets that may use materials containing BPA. Human exposure is measured and reported in a variety of ways. This has caused confusion in the marketplace.

Summary

Fig. 2 – This image shows a polycarbonate component of a housing unit with a color additive to mask discoloration from the sterilization process while preserving transparency.
Despite extensive scientific data about the safety of polycarbonate, decisions are sometimes made regarding material use based on erroneous information or conclusions. Consequently, polycarbonate is sometimes being deselected and replaced with various alternative materials. Replacement materials often have lesser performance compared to PC. When product performance is compromised, new patient risks can potentially arise. Other materials generally have less history of use in the application, thus introducing new design and functional concerns.

Polycarbonate delivers unique benefits and is irreplaceable for many healthcare applications. It is used in a variety of life-supporting apparatus such as hemodialyzers, anesthesia containers, blood oxygenators, arterial filters, intravenous connectors, and endoscopic appliances. The material clearly enables some of the advanced procedures that are common today.

In an operating or emergency room, for example, a critical device made of polycarbonate is lightweight for easy handling, strong and tough to prevent breakage, and importantly, clear and transparent to allow for quick, accurate, visual inspection or observation of the level, flow rate, or condition of fluids moving through a device. It has the clarity of glass, but with toughness and durability that is unmatched. Many medical devices that were once made of glass are now made of polycarbonate. Others are new uses for which glass is not practical. (See Figure 1)

In addition to passing biocompatibility, FDA, and physical property requirements of the medical device, parts made from the resin must be able to undergo sterilization. PC has been shown to have excellent retention of physical properties when sterilized using the most common methods such as as ethylene oxide gas, gamma and e-beam radiation. The polycarbonate performance is maintained after sterilization of the device. Resulting parts are durable and have a long shelf life. (See Figure 2)

Polycarbonate is a proven material and offers significant benefits for medical applications. It is one of the most thoroughly tested plastics used today and has a safety track record of more than 50 years. It provides features such as strength and clarity that cannot be compromised for many medical devices. It can be sterilized using all of the common methods. For these reasons, it is the material of choice for demanding medical applications today and well into the future.

This article was written by Cheryl Weckle, Development Scientist, Styron Medical Applications, Styron, Berwyn, PA. For more information, Click Here.