The Germ Fix

Jan. 1, 2000
This murder mystery isn`t all that hard to figure out - no surprise endings. The clues about disinfectants are in the labels, as well as an awareness of what the active ingredients accomplish

This murder mystery isn`t all that hard to figure out - no surprise endings. The clues about disinfectants are in the labels, as well as an awareness of what the active ingredients accomplish

Frederick T. Smith

Hard surface germicides should be more carefully scrutinized by those who use them. These pesticide products are used by health care professionals (including dentists, physicians, emergency medical providers, daycare personnel, and homeowners) to kill bacteria, viruses, and fungi on various surfaces. They are available in liquids, pump-sprays, aerosols, and towelettes. Not all are created equal, nor are all effective for all uses. Some are highly toxic, even potentially carcinogenic, while others are much safer and no less effective.

All hard-surface germicides, depending on their intended uses, must be:

- Registered by the Environmental Protection Agency (EPA) as antimicrobial pesticides, or

- Approved as medical devices by the Food and Drug Administration (FDA).

Sometimes, the same product requires both EPA registration and FDA approval. For example, EPA has jurisdiction over sanitizers, disinfectants, and nonliquid sterilants, which many people are surprised to learn are regulated as pesticides. FDA jointly regulates disinfectants used to pre-clean medical devices before sterilization (dental instruments and instrument trays, for example) and exclusively regulates all liquid chemical sterilants.

Generally speaking, germicides can be placed into seven categories based on the specific active ingredient - the chemical or combination of chemicals - in the product that actually kills the target microorganisms. The categories are:

- Glutaraldehyde-based

- Phenol-based

- Iodine-based

- Sodium hypochlorite (bleach)-based

- Sodium bromide/sodium dichloroisocyanurate dihydrate-based

- Quaternary ammonium chloride-based

- Quaternary ammonium chloride/alcohol-based antimicrobials.

Within each of these categories, a given product may be a sanitizer (inhibits the growth of vegetative germs), a disinfectant (kills vegetative germs), or a sterilant (kills vegetative germs and spores).

Sanitizers are the least effective products; sterilants are the most effective. However, if a product is a sterilant, it is also a sanitizer and a disinfectant. If a product is a disinfectant, it is a sanitizer too, but not a sterilant. Sanitizers are just sanitizers.

All germicides must be registered by EPA. The exception is for liquid chemical sterilants, which require FDA approval. Regardless of whether EPA or FDA has jurisdiction, however, a product`s label must include an ingredient statement that lists the concentration of each active ingredient. This makes it easy to determine the content of any product, and whether the active ingredient is appropriate for your intended use. In addition, all germicides (except for liquid chemical sterilants) must clearly list an EPA registration number on the product`s label. If there is no such number on the label, then the product is illegal (which, unfortunately, is not uncommon).

For EPA registration purposes, every antimicrobial product must satisfy specific regulatory requirements, including those pertaining to safety and efficacy.

Safety is demonstrated in two ways: 1) by testing the active ingredient(s) alone in a series of both acute and longer-term toxicity studies, and 2) by a series of acute toxicity studies performed with the same product that the consumer uses (the so-called "end-use" product).

The studies conducted using the active ingredient(s) - called generic data requirements - are performed separately from, but in addition to, those done with the end-use product. These toxicity studies show the toxicity potential of the technical grade active ingredient (TGAI) after repeated exposure over weeks, months, or, in some cases, years. Both in vitro and in vivo studies are required. The TGAI is the active ingredient without any intentionally added inert ingredients such as water, fragrance, or color.

The acute toxicity studies on the end-use product - called end-use data requirements - include oral toxicity, dermal toxicity, inhalation toxicity, eye irritancy, dermal irritancy, and dermal sensitization (the ability to cause an allergic response due to repeated contact with the product).

Minimum efficacy test requirements for sanitizers, disinfectants, and sterilants differ greatly from one another. Nonetheless, all efficacy data must be submitted to, reviewed, and accepted by EPA, including data supporting claims made for a product beyond EPA`s minimum required performance criteria. For example, all disinfectants must be efficacious against Staphylococcus, Pseudomonas, and Salmonella, but are not necessarily required to be tuberculocidal. If a company wants to make a tuberculocidal claim for its product, it must submit additional efficacy data showing that it specifically kills TB bacteria.

Disinfectants comprise the largest number of antimicrobial products. These products are commonly used in dental offices and hospitals on hard, nonporous surfaces and to pre-clean instruments that are then separately sterilized. Generally, disinfectants and sterilants kill other microorganisms as well, including viruses (HIV, adenovirus, or hepatitis, for example), other bacteria (mycobacterium which cause tuberculosis, and antibiotic-resistant bacteria, for example), and fungi (Trichophyton mentagrophytes, which causes athlete`s foot, for example).

However, EPA requires that any product registered for use against those additional pathogens must specifically list them on the label. In addition, the labels must clearly state the contact time required for a product to be effective.

The FDA requires that safety and efficacy be demonstrated for sterilants and disinfectants used on medical devices, similar to EPA`s registration requirements.

A description follows of the seven active ingredient categories that are commonly used in the dental field. The discussion reviews their respective strengths and weaknesses. Keep in mind, however, that these active ingredients are evaluated in the context of hard surface disinfectants used in dental offices. Although an active ingredient may have disadvantages for such uses, it may be entirely appropriate for other uses.


Glutaraldehyde-based antimicrobial products are registered as both disinfectants and sterilants depending on the mode of application (such as spray/wipe vs. soak). For sterilization, the instrument generally must be completely immersed for 10 or more hours. Contact times for disinfectant glutaraldehyde spray formulations with tuberculocidal claims generally start at 20 minutes.

Glutaraldehyde is strongly irritating to the nose, eyes, and skin, and can cause allergic-contact dermatitis from occasional or incidental occupational exposure. Some glutaraldehyde formulations are also corrosive to certain metals.

Based on these known health hazards, the Occupational Safety and Health Administration (OSHA) now requires that glutaraldehyde products be used under proper ventilation, and the permissible exposure limit (PEL) is 0.2 ppm. In accordance with OSHA`s PEL, glutaraldehyde products should not be sprayed, thereby avoiding probable user-exposure and the associated health effects due to overexposure.

In light of these hazards, liquid glutaraldehydes should probably not be used at all for hard-surface disinfection because better, less toxic alternatives are available for this application.


Phenol-based products are registered as disinfectants and are among the most commonly used products in the dental field. Required contact times are typically 10 minutes. Some phenol-based products, though, have one-minute efficacy claims against HIV, which is typical for most disinfectants that are registered for use against this microorganism.

According to EPA ( hlthet/phenol.html), phenol is "flammable, corrosive, and very toxic," and "ingestion of even small amounts may cause vomiting, circulatory collapse, paralysis, convulsions, and coma." Phenolics can cause sinus and respiratory problems, as well as headaches due to overexposure.

Despite these warnings, a variety of phenol compounds appear in common consumer products, and many are considered to be safe. Medical, sanitary supply professionals, and dental professionals use phenol-based products.

Some concerns are sometimes raised about the difficulty in removing the film left behind by phenol-based disinfectants, but a wet paper towel usually is sufficient in removing the residue. Some phenol solutions should be discarded and remixed daily.

All EPA-registered products must include the following statement on their label: "It is a violation of Federal law to use this product in a manner inconsistent with its labeling." Products registered by EPA have their own directions for use, and, in many cases, these directions are very specific.

A product`s EPA-approved label claims are based on efficacy data that are generated using the same directions for use that appear on the product`s label. For example, the directions for use on many hard surface disinfectants require two steps - first, remove gross filth (often using the disinfectant itself as a cleaner), then re-apply the product to the pre-cleaned surface for the specified contact time to kill any remaining pathogens.

Naturally, if these directions are not followed, it is quite possible that the product will not perform as labeled.

Sodium Hypochlorite

Bleach is a well-known antimicrobial, and is effective under certain conditions. (To be sold as an antimicrobial, however, it must be EPA registered.) Because bleach reacts with (oxidizes) organic material such as blood, tissue, saliva, or microbes, the more organic material that is present, the more it has to oxidize. As a result, if the organic load is too high relative to the amount of bleach available, there may not be sufficient bleach available to kill the target microorganisms. In other words, organic material diminishes bleach`s biocidal activity.

Due to bleach`s reactivity potential (corrosiveness), it should not be used on certain metals (chrome-cobalt alloy or aluminum, for example).

Odor is also an issue. Although masking agents are often used by manufacturers to help overcome this, the fact remains that there is still a strong chlorine odor even with the masking agents. While bleach`s kill times are better than average, its odor and chemical instability are major drawbacks.

Sodium Bromide & Sodium

Sodium bromide and sodium dichloroisocyanurate dihydrate (NaDCID) act on the same principle as bleach: They oxidize organic matter. When NaDCID is added to water, chloride is produced. Unless the water is free of organic material, the chloride then forms hypochlorous and hydrochloric acid. These are the ingredients that actually kill the microorganisms. A small amount of sodium hydroxide (lye) is also formed when either bleach or NaDCID is used. Sodium bromide reacts similarly. When added to water, hypobromous acid is formed.

There is only one currently registered product, MicroStat 2, with this ingredient combination. Each ingredient is a separate, solid pellet that is added directly to a premeasured quantity of water. As discussed for bleach, odor and instability are major drawbacks. If kept away from heat, moisture, and sunlight, the tablets are reasonably stable though.


These products are registered as disinfectants. Iodine-containing products are generally considered to be outdated, replaced by newer, superior, faster, less-damaging antimicrobials such as quaternary ammonium chloride/alcohol products.

Iodophores are widely known to discolor treated surfaces, though newer formulations are less so. Iodophores have relatively slow kill times (10 minutes and up), the dilutions and contact times are critical for efficacy, they must be discarded and remixed daily, and may be inactivated by hard water. With the availability of significantly faster, non-iodine-based products, there is little justification for their continued use other than low price and low toxicity, albeit at the expense of staining and slow kill times.

Quaternary Ammonium Chlorides

Quaternary ammonium chloride-containing products are registered by EPA as disinfectants and are the most commonly used type of antimicrobial for both healthcare and consumer use. Numerous kinds and combinations of quats are known for having low toxicity and, depending on the formulation, relatively fast contact times against the widest range of organisms of any active ingredient. They are easy to use and are noncorrosive.

Quat evolution, which began in the 1930s, is now in its fifth generation. Quats can be formulated with or without detergent to assist in cleaning, as well as disinfecting. The newest fifth-generation quats are the most effective, safest, and most flexible quats developed thus far.

Generally, disinfectants that contain quats as the sole active ingredient require 10-minute contact times for most organisms, except HIV, which is typically one minute or less.

New Generation Quat/Alcohol Technology

Combining the new, fifth-generation quats with alcohol - either isopropanol or ethanol - results in even lower required contact times (less time required to kill the target microbes). Faster kill times enable health care professionals, such as dentists, to disinfect surfaces quickly.

Due to the presence of the alcohol, which evaporates quickly and leaves little, if any, perceivable residues, dentists are able to effect faster patient turn-around. With managed-care programs and HMOs, patient turnover is critical. Previously, surfaces treated with an antimicrobial generally needed to remain wet for 10 minutes or longer. Now, those same surfaces, when treated with one of the new generation quat/alcohol products, can be used in half that time without fear of cross contamination. Rinsing is not required.

Two types of quat/alcohol products are available: Those with less than 40 percent alcohol, and those with greater than 40 percent alcohol. Faster kill times are obtained with the higher concentration products. An excessive amount of quat (greater than 0.30 percent) causes staining and does not significantly increase product performance. Quat products with higher alcohol contents generally are tuberculocidal, whereas pure quat products and those with lower alcohol concentrations generally are not.

Clearly, with the plethora of antimicrobial products from which to choose, selecting the one that meets your needs is crucial. Ease of use/convenience, kill times, esthetics (odor, residue, appearance, staining), effectiveness as determined by label claims, compatibility, cost, and toxicity are the factors which ultimately will be weighed when making your choice.

It also is critically important that the product chosen works as claimed - both to protect the user and the patient against potentially transmittable diseases.

In conclusion, look at the required ingredient statement on the product`s label to determine its contents. Also look at the pathogenic microbes listed on the label and the required contact times. Are they appropriate for your intended use? Then look at whether the product is registered by EPA, as evidenced by an EPA registration number on its label.

Frederick T. Smith is a senior consultant with the regulatory consulting firm of ChemReg International.