Why Neutralize? A Look at the Safe Disposal of High-Level Disinfectants

By Philip Coles

Editor's note: This article originally appeared as the Vendor Viewpoint column in the May 2012 print issue of ICT.

It is illegal in some parts of the country to dump used OPA or glutaraldehyde down the drain without neutralizing it first.  It is a popular misconception that used OPA or glutaraldehyde is no longer dangerous (biocidal) after it has passed its reuse date or it has failed a MRC test.  Not only can used disinfectants adversely affect the sewer system, but they can be dangerous to the healthcare worker as well.

 
OPA and Glutaraldehyde
The most widely used High Level Disinfectants (HLDs) are OPA and glutaraldehyde. They are used for heat-sensitive devices such as endoscopes and endocavity ultrasound transducers. These disinfectants can be reused for anywhere between 14 and 30 days. In addition to the maximum reuse period, these HLDs have to pass the manufacturers Minimum Recommended Concentration (MRC) testing to confirm efficacy of the product. This should be conducted before each disinfection cycle by using the manufacturers test.  In the case of high volume automated reprocessors, the MRC test can often fail long before the reuse date expires. As mentioned earlier, a failed MRC test does not mean that it is safe to dump the HLD without first deactivating it.

Whats the Danger?
The simple act of pouring used disinfectant into a sink or hopper breaks the surface tension and results in a rapid off gassing of vapor. Testing routinely shows levels above 1 ppm in the breathing zone during disposal (twenty times higher than the ACGIH level of 0.05 ppm). Pouring can also result in splashes and spills that add to the off gassing of vapor.  Even worse is the risk of a dropped container causing the HLD to splash right into a persons face. The simple and inexpensive act of neutralizing the used chemical before disposal eliminates these very real risks.

 
Is it Illegal?
In some areas of the country it is illegal to dispose of used OPA and glutaraldehyde into a Publicly Owned Treatment Works (POTW) without first neutralizing.  The manufacturer of OPA has informed DTSC (Department of Toxic Substances Control) that the solution at use-dilution (failed MEC test) fails the California aquatic bioassay toxicity characteristic and thus is hazardous waste when discarded without treatment. The conditions of treatment are that:
1. The waste (HLD) is generated by a medical facility during the disinfection of medical devices.
2. That it is treated at the site where it was generated.
3. That the sole active chemical of the neutralizing solution is glycine.

Exposure Levels
The current maximum vapor exposure level of glutaraldehyde recommended by ACGIH is 0.05ppm. It is an instantaneous level, which means you cannot exceed it for a single moment. The highest risks occur when pouring fresh HLD into a container (or an automated reprocessor), during disposal, or any time the surface tension is disturbed. The MSDS warnings for both OPA and glutaraldehyde read almost identically, requiring the use of personal protection equipment including mask/glasses, gloves and gowns as well as at least 10 air exchanges or the use of a ductless fume hood or local exhaust.

Automated Reprocessors
HLDs are typically used in an automated endoscopic reprocessor (AER) or in a manual soaking container. Obviously, open soaking containers pose a greater risk during disposal than an enclosed AER. AERs are plumbed directly into the drain so the used chemical can be dumped directly into the sewer system without first deactivating it, but vapor can easily rise up from the drain. 

It is a common practice to pour neutralizer directly into an AER prior to disposal. This is an unsafe practice (and is strongly discouraged by the AER manufacturers). Most AER reservoirs do not get rinsed after disposal and residual neutralizer can remain in the reservoir and degrade the fresh HLD. To avoid this problem it is first necessary to pump used disinfectant into a holding tank where it can be deactivated prior to disposal. 

Semi-automated mobile disposal systems allow several gallons of used OPA or glutaraldehyde to be safely deactivated.  A proprietary glycine based powder neutralizer is poured into the tank before the transfer of waste from the AER.  After deactivation the inert HLD is safely pumped to drain. Vapor, splashes and spills are eliminated and the sewer system is protected.

Active Ingredient: Glycine
In order to comply with the California disposal regulations, glycine should be the sole active chemical of neutralizer. Sodium bisulfate is very effective at neutralizing glutaraldehyde and OPA, but it creates a new compound that is toxic. Glycine is effective because it is an amino acid, essentially the building blocks of proteins. Both OPA and glutaraldehyde attack protein, so by adding a sufficient amount of glycine to the used disinfectant, the HLD is quickly overwhelmed and neutralized without creating toxic new compounds.  Neutralizers should be tested independently with a strict chain of custody and they should undergo rigorous fish toxicity tests as well. Neutralizers for OPA and glutaraldehyde can be readily found on the Internet.

Philip Coles is president of PCI Medical.