Biomedical Engineering Reference
In-Depth Information
EH&S
AND
S
TERILIZATION
While there are dozens of ways to sterilize a device, the three most
common means are with ethylene oxide, gamma rays, and electron beam
radiation. Ethylene oxide (EtO) is a colorless gas that is very effective in
killing pathogens without adversely impacting the material integrity of the
device. It is transporting and production concern due to both its flammable
nature as well as acute/chronic human toxicity. Several agencies worldwide
classify EtO as a probable human carcinogen, with occupational exposure
limits in the one to five parts per million range (U.S. Occupational Health and
Safety Administration, 2010). Due to very stringent, in-process controls, it is
very unlikely that human exposures will occur today in the industry. However,
there is always the potential for a process system leak or an operator mistake
which may lead to unsafe airborne exposures to personnel. Since EtO is in the
gaseous state, there is little or no concern for the generation of hazardous solid
or liquid wastes on location.
Gamma ray sterilization is also commonly used in the biomedical device
industry, typically employing a source of cobalt-60 (Co-60) to destroy
microbes on such devices as syringes and catheters. Gamma rays are very
effective in destroying any residual microbe by attacking the DNA, and its use
provides several advantages over EtO including optimal device penetration
and no residuals. Since Co-60 is a radioactive source, most nations have a
regulatory agency different than labor or environment that focuses on specific
regulatory affairs for nuclear materials. Yet, some regulatory overlap is usually
encountered, especially when it comes to dealing with any wastes. A waste
with both radioactive and chemical toxicity concerns is known as a ―mixed‖
waste. A mixed waste has several regulatory challenges due primarily to two
or more agencies getting involved in the regulatory process.
Another commonly used means for sterilization is known as electron beam
radiation sterilization. Many of the same regulatory concerns as those for
gamma ray sterilization are typically encountered in its transportation, use, and
disposal. To protect the worker, the concept of dosimetric release is normally
followed in one form or another. Dosimetric release is determined through the
use of instruments known as radiation dosimeters, and the verification of both
the minimum and maximum doses encountered provides the mechanism for
release and shipment (Handy and Lafreniere, 2007). Both human OELs and
environmental radiation limits are typically in place in most countries, and the
concept of ALARA (as low as reasonably achievable) is a common exposure
strategy.
