Donning by Design: Sterile Cleanroom Gowning Evolves to Help Minimize Contamination Risk

A novel cleanroom apparel design incorporates modern concepts to help minimize contamination. Take a tour of the design.
May 01, 2009
Volume 33, Issue 6

In the pharmaceutical industry, the investments needed to bring a product to market are staggering. It is widely reported that the fully capitalized cost to develop a new drug can range from $800 million to nearly $900 million.

The steep price of product rejects and recalls makes it crucial to ensure high product yields by maintaining strict cleanroom cleanliness and sterility. For this reason, the US Food and Drug Administration mandates that any product that is injected, used in the eye, or used on open wounds must be sterile (i.e., free from viable microorganisms). That is because, if contaminated with microorganisms, these pharmaceutical products can adversely harm patients.

Microorganisms introduced into a cleanroom environment need only three things to grow: moisture, food, and temperature—all of which exist in a cleanroom. Consequently, all incoming air, water, chemicals, and materials must be filtered or sterilized to meet high standards of purity and microbiological control so as not to contaminate processes or products in production. Also to be "filtered," in a sense, is the cleanroom operator, who, is the dirtiest element in a cleanroom. Consider the following:

  • One square inch of hand surface has an average of 10,000 microorganisms
  • Every square inch of the human body has an average of 32 million bacteria on it
  • Every minute of the day, people lose from 30,000 to 40,000 dead skin cells off the surface of their skin
  • When stationary, people generate approximately 100,000 particles of 0.3 µm or greater, and on the move, this number increases to approximately 5 million.

Keeping the operator's dirt and germs out of a sterile cleanroom environment and away from sensitive products and processes is the main objective of the sterile cleanroom suit. The suit must protect the environment from viable particles such as bacteria and yeasts and nonviable particles such as hair, dead skin cells, and dandruff. To that end, it is critical for cleanroom operators to select cleanroom suits that provide not only the highest levels of inherent sterility, but also the greatest chances of maintaining that sterility through the gowning process.

Sterile cleanroom suits: an overview

Although there are no federal regulations for sterile cleanroom garments used in the pharmaceutical industry, guidance for the industry is available from The Institute of Environmental Sciences and Technology (IEST), which publishes a recommended practice IEST-RP-CC003.3 entitled, "Garment Considerations for Cleanrooms and Other Controlled Environments." The recommended practice provides guidance for selecting fabric, garment construction, cleaning and maintenance of cleanroom garments, and the testing of cleanroom apparel for use in aseptic and nonaseptic cleanrooms.

Although cleanroom garments can either be disposable or reusable, according to industry analysts, most sterile facilities will opt for disposable garments because of contamination concerns relating to reusable garments returned from laundering facilities. In some companies, disposables may be used at some locations and reusables at others. The choice can depend on the classes of the various cleanrooms at various locations.

Disposable garments may be easier to manage from a cost standpoint as well, because the price for reusable garments often carry "hidden" charges such as delivery and pick-up fees (and related energy surcharges), lost/unused garment charges, laundering, sterilization charges, and so forth.

For more than 40 years, disposable cleanroom suits have been made from flash-spun polyethylene fabric. According to industry analysts, flash-spun polyethylene provides filtration efficiency for submicron sized particles and microorganisms and is suitable for light splash protection from nonhazardous liquids. Disposable suits also can be made from spunbond-meltblown-spunbond (SMS) fabric, which has outer layers of spunbond polypropylene for strength and cloth-like comfort, with middle layers composed of a matrix of microfibers, which creates a torturous path for fine particles and liquids. Reusable cleanroom suits are typically made from woven polyester-blend fabrics, which may degrade after multiple laundering and sterilization cycles.

Operators in a sterile cleanroom environment in the pharmaceutical industry will wear three to four disposable suits in a day, each suit being worn for two to three hours at a time. Cleanroom protocol dictates that garment changes must be made each time the cleanroom is re-entered. Once discarded, these suits can be incinerated, or they can be repurposed through a garment recovery service that will take the used garments and sell them back into non-sterile applications.

Cleanroom garments in the United States may be sterilized using several methods, including gamma irradiation, ebeam sterilization, and ETO sterilization. Gamma sterilization is widely considered to be the most cost-effective method. The desired sterility assurance level (SAL) for garments used in sterile pharmaceutical manufacturing is 10-6 , which translates into a one-in-a-million probability of a garment being nonsterile. Once sterile, cleanroom suits must be packaged in a way that this sterility is maintained throughout handling, transportation, and storage.

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