Toxicity of Disinfectants

By Benjamin D. Tanner, Ph.D. - President, Antimicrobial Test Laboratories

This page provides information regarding the toxicity of disinfectants. Its purpose is two-fold. The main goal is to help interested, technically minded users of disinfectant products understand chemical risks posed by these common household products. The secondary purpose is to provide a jumping-off point for chemists, inventors, and formulators who are working on disinfectants and wish to understand how they are regulated, ranked, and labeled for toxicity to humans by the US Environmental Protection Agency (EPA).

Disinfectants must be registered with EPA prior to sale in the United States. In other words, before they can be put on a store shelf, the EPA must review data presented by the manufacturer detailing the disinfectant's chemical composition, germ-killing abilities, and chemical toxicity to humans. In consideration of this data, EPA then works with the manufacturer to arrive at an appropriate product label.

Disinfectants with an active ingredient chemical that has not yet been registered with EPA require a number of fundamental, long-term toxicity studies. Such situations are outside of the scope of this article and are reasonably rare.

More commonly, the active ingredient of a disinfectant chemical is already registered for use as a pesticide, so the type of toxicity data EPA requires prior to permitting sale is different. In thse cases, EPA requires acute toxicity data (data describing what happens immediately after exposure to the complete disinfectant formulation).

For the vast majority of disinfectants, EPA requires manufacturers to carry out six acute toxicity studies - even if those formulations are "powered" by a characterized, registered active ingredient. These studies are paid for by the manufacturer and are usually done at contract animal research laboratories. This so-called "six-pack" of acute toxicity studies is used by EPA to determine the acute toxicity of the disinfectant product. Then the EPA registration/label review process translates the outcomes of the toxicity studies into health and hazard information that becomes part of the product label.

The six acute toxicity studies required by EPA follow:

Acute Oral Toxicity (OPPTS 870.1100)
Acute Dermal Toxicity (OPPTS 870.1200)
Acute Inhalation Toxicity (OPPTS 870.1300)
Acute Eye Toxicity (OPPTS 870.2400)
Acute Dermal Toxicity (OPPTS 870.2500)
Dermal Sensitization (OPPTS 870.2600)

Each of the toxicity tests listed above generates a result. Translated to a language everybody can understand, acute toxicity tests indicate things like "How much disinfectant was needed to kill 50% of exposed rats," or "How bad was the damage when the disinfectant was put onto a rabbit's eye, did it heal, and how long did healing take."

Based on the results from the toxicity studies, EPA assigns disinfectants to one of four categories, each of which is associated with a particular signal word that appears on the product label. Those signal words follow:

Danger - Category I (associated with highly toxic products).
Warning - Category II (the product us moderately toxic).
Caution - Category III (the product has limited toxicity).
No Signal Word Required - Category IV (the safest category).

The worst result from the six acute toxicity tests determines the toxicity category of the product. Typically but not always, ocular (eye) or dermal toxicity tests give the worst toxicity result for a disinfectant product.

In product marketing literature, one frequently finds wishy-washy terms like "limited toxicity" or "moderately toxic." Just what does that mean? The table below (adapted from Chapter 7, Table 1 of the EPA label review manual), indicates which toxicity test results are associated with different toxicity categories and precautionary labeling in the United States.

The table above still may be somewhat confusing to the average reader. Let's take the information in the second column, first row as an example. If a product is labeled as "Category 1" for Acture Oral Toxicity, then that means that only a relatively low disinfectant concentration of 50 mg per kg of animal body weight produced a toxic result in the test animals corresponding to a "breakpoint" within the test method. In the case of an acute oral toxicity test, a likely breakpoint - though I haven't researched it in detail - is death of 50% of the pool of test animals that were fed the disinfectant.

Hopefully the information on this page has been helpful in your quest to understand toxicity and toxicity ratings for disinfectants and sanitizers. Thank you for reading!

As a final note, Antimicrobial Test Laboratories does not perform animal testing or toxicity testing, and hopes to drive the industry to non-animal testing models as soon as possible. In the spirit of that effort, please take note of a list of non-animal toxicity tests that can be used to spare animals from pre-GLP toxicity testing (use of animals for rangefinding or project risk assessment exercises).