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Why Neutralize High Level Disinfectants

Wed 14th Feb, 2024 General

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 (HLD’s) are ortho-phthalaldehyde (OPA) and glutaraldehyde. They are used for heat-sensitive devices such as endocavity ultrasound transducers, intraoral digital x-ray sensors and endoscopes. These disinfectants can be reused for anywhere between 14 and 30 days as directed by the manufacturer. In addition to the maximum reuse period, these HLD’s must pass the manufacturers Minimum Recommended Concentration (MRC), formerly known as MEC, Minimal Effective Concentration, testing to confirm efficacy of the product. For most manufacturers, this should be conducted prior to each disinfection cycle by using the testing supplies from the manufacturer of the solution. 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.

What’s 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 0.05 ppm, the level established by the American Conference of Governmental Industrial Hygienists (ACGIH)). 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 person’s 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. A manufacturer of OPA has informed the Department of Toxic Substances Control (DTSC) 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 threshold limit value (TLV) of a chemical substance is believed to be a level to which a worker can be exposed day after day for a working lifetime without adverse effects. Strictly speaking, TLV is a reserved term of the American Conference of Governmental Industrial Hygienists (ACGIH). TLV is measured three ways. TLV-C is the Ceiling Exposure Limit – the concentration that should not be exceeded during any part of the working exposure, even instantaneously The current maximum TLV for glutaraldehyde recommended by ACGIH is 0.05ppm. For our clients, we regularly conduct dosimetry to determine TLV-TWA. TLV-TWA is the allowable Time-Weighted Average level for a normal 8-hour workday or 40-hour week. Dosimetry should be conducted and repeated any time new employees or new processes are introduced into the practice.

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 SDS 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

HLD’s 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. AER’s are plumbed directly into the drain so the used chemical is 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 can be an unsafe practice (and is strongly discouraged by the AER manufacturers). Most AER reservoirs are not rinsed after disposal and residual neutralizer can remain in the reservoir and degrade the fresh HLD. To avoid this problem, it is suggested operators 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 many state’s disposal regulations, including California, glycine should be the sole active chemical of neutralizer. 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 enough glycine to the used disinfectant, the HLD is quickly overwhelmed and neutralized without creating toxic new compounds.

Neutralizers for OPA and glutaraldehyde can be readily found on the Internet or purchased through your medical or dental supply house.

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