How to Dispose of High Level Disinfectants Safely

Dumping used OPA or glutaraldehyde down the drain without first deactivating it can be dangerous to you and, in some cases, illegal. 

A popular misconception is that used OPA or glutaraldehyde is no longer biocidal (read dangerous) after its reuse date has passed or it has failed a MEC test. In fact, both OPA and glutaraldehyde remain highly biocidal after the reuse date or after failing the MEC test.

OPA & Glutaraldehyde

OPA and glutaraldehyde are the most widely used liquid High Level Disinfectants (HLD’s) for heat sensitive devices such as endoscopes and endocavity ultrasound probes. OPA and glutaraldehyde based HLD’s can be reused for up to 14 days (some for up to 30 days).  In addition to the maximum reuse period, the high level disinfectant has to pass the manufacturers Minimum Effective Concentration (MEC) testing to confirm efficacy of the product.  This should be conducted before each disinfection cycle that is done by using the manufacturers test strips and comparing the color against a color chart.  In the case of high volume automated reprocessors, the MEC test can often fail long before the reuse date expires. As mentioned earlier, a failed MEC test does not mean that it is safe to dump the HLD without first deactivating it.

What’s the Danger?

It is dangerous to you because 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 (this is twenty times higher than the ACGIH level of 0.05 ppm). It can also result in splashes and spills adding to the off gassing of vapor.  Even worse is the risk of a dropped container causing the HLD to shoot up 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.  The manufacturer of OPA has informed DTSC (Department of Toxic Substances 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.

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Exposure Levels

The current maximum vapor exposure level of glutaraldehyde recommended by The American Conference of Governmental Industrial Hygienists 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

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.  The latter are plumbed directly into the drain and at the touch of a button the used chemical can be dumped directly into the sewer system without first deactivating it. The drain line from an AER is much like a washing machine drain and is open to atmosphere, so 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.

The Medi-Newt™ from Medivators is a semi-automated mobile disposal system that allows up to 12 gallons of used OPA or glutaraldehyde to be safely deactivated.  A proprietary glycine based powder neutralizer (Neutra-Hyde™) 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.

Glycine Active Ingredient

To comply with the California disposal regulations, the sole active chemical of neutralizer should be glycine.  Sodium bisulfate is another chemical 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.  To prove this, the deactivated product is subjected to tough fish toxicity tests.

Glute-Out® Neutralizer

Glute OUTCIVCO Medical Solutions distributes Glute-Out brand neutralizer for OPA and glutaraldehyde.  Glute-Out is a glycine-based neutralizer with a proprietary buffer that accelerates the process of neutralization.