Biocides

The Use of Biocide or Antimicrobials (Revisited): Has there been a change in the way that IICRC S500 refers to biocides?

The simple answer to your question is YES. Prior to the S500 3^rd edition, the IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration referred to biocides as chemicals that are used to kill micro-organisms and those that retard or suppress growth as antimicrobials. The following is additional information that was included in an article published in this magazine in September 2005:

Biocides are sometimes referred to as bactericides or fungicides when they are designed to kill bacteria and fungi respectively. In addition, antimicrobials are sometimes referred to as bacteriostats or fungistats when they are designed to inhibit growth of bacteria or fungi. If you break down the term biocide into its prefix and suffix, you come up with bio-, which means life and -cide, which means kill. Therefore, they are life killers. The suffix -stat means stasis or static. Often the products referred to as fungistats only inhibit microbial growth and do not necessarily kill fungi. They maintain a static environment.

These definitions are consistent with the American Conference of Governmental Industrial Hygienists (ACGIH) publication entitled Bioaerosols: Assessment and Control. Note the following quotes from this publication.

"Biocides are toxic chemicals or physical agents capable of killing or inactivating one or more groups of microorganisms, that is, vegetative bacteria, mycobacteria, or bacterial spores; vegetative fungi or fungal spores; parasites; or viruses." (16.1.1)

Biocides tend to be aqueous solutions [e.g., alcohols (ethyl, isopropyl), hydrogen peroxide, aldehydes (formaldehyde, glutaraldehyde), phenolic compounds, quaternary ammonium compounds (cationic detergents), halogens (chlorine, iodine, and bromine compounds)]. Biocides are generally aqueous and once they are applied or evaporate, they are no longer effective.

"Antimicrobial agents are chemical formulations incorporated into or applied onto a material or product to suppress vegetative bacterial and fungal growth as it occurs (Table 16.1). Such compounds may be used to retard microbial growth in potential sources. Typically, antimicrobial agents are incorporated into products during manufacture (e.g., carpet material, ceiling tiles, and air filters). Additionally, antimicrobial agents are often included in products (e.g., paints, coatings, and sealants) that are applied to various building and equipment surfaces." (16.1.2)

"Bacteriostatic agent: chemical agent that suppresses or retards bacterial growth on direct contact with the treated material.

Fungistatic agent: chemical agent that suppresses or retards fungal growth on direct contact with the treated material." (Table 16.1)

Antimicrobials are often metallic compounds that continue to leave a residue that has prolonged effectiveness. Some are chemically bound so that they can be added as ingredient in paint, plastic or fiber production. Some antimicrobial fibers are used in garments and flooring materials.

In the 3^rd edition of the S500 it was decided by the S500 Consensus Body to use the United States Environmental Protection Agency's (USEPA) definitions. The S500 3^rd Edition reference Guide makes the following statement:

Definition and Regulation
Antimicrobials are substances used to destroy (biocides) or suppress growth (growth inhibitors/static agents) of microorganisms (i.e., bacteria, viruses, or fungi) on inanimate objects, surfaces, and materials. The United States Environmental Protection Agency (USEPA) Antimicrobials Division registers and regulates antimicrobial products (which the Agency refers to as a pesticide) under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Some jurisdictions require commercial applicators of antimicrobial products to be licensed, certified, or to be specially trained.

Another well respected publication has similar definitions as the ACGIH publication, Disinfection, Sterilization, and Preservation by Seymour S. Block. While this book does use similar terms, it also refers to biocides as antimicrobial in several instances. A biocide is defined as "a substance that kills all living organisms, pathogenic or nonpathogenic." A bacteriostat is defined as "an agent, usually chemical, that prevents the growth of bacteria but does not necessarily kill them or their spores." Finally, an antimicrobial agent is defined as "any agent that kills or suppresses the growth of microorganisms." This last definition is somewhat consistent with the way that the Environmental Protection Agency (EPA) refers to biocides and antimicrobials. Interestingly, the EPA also refers to both biocides and antimicrobials as pesticides. On the EPA website under the heading "What are Antimicrobial Pesticides?" it states "Antimicrobial pesticides are substances or mixtures of substances used to destroy or suppress the growth of harmful microorganisms whether bacteria, viruses, or fungi on inanimate objects and surfaces" (http://www.epa.gov/oppad001/ad_info.htm). In some states you might be required to have a pest control applicator’s license in order to apply these products legally in your customers' homes.

I understand the desire to change to the EPA terminology. However, the change to the USEPA terminology is going to be confusing to the reader. For example, we will be referring to quaternary ammonium chloride (quats) as a biocide and as an antimicrobial or pesticide.

—Jim Holland

Ozone Genrators: Are ozone generators a substitute for mold removal?

Ozone generators are manufactured in two basic types. One treats water and the other treats air. There has been a lot of controversy about what ozone generators can and cannot do. The general consensus is that neither type of ozone generator can be used for removing or effectively treating visible fungal growth.

Ozone (O₃) is a colorless, pungent smelling gas that is a form of oxygen. It is composed of three atoms of oxygen, rather than the two oxygen atoms of ordinary atmospheric oxygen (O₂). Ozone is a highly reactive, unstable molecule that is heavier than air. It has been successfully used for certain types of water purification and for the treatment of residual odors. In controlled circumstances it has been used to react with residual smoke odor to neutralize those odors. It does not, however, get rid of the soot deposits or the physical damage caused by a fire. Similarly, ozone does not eliminate mold-related particles such as spores and hyphae, nor does it remove the damage caused by water or the growth of mold into materials.

Ozone has been successfully used to treat water for swimming pools and spas to reduce or eliminate the chlorine disinfection. According to the American Conference of Governmental Industrial Hygienists publication Bioaerosols: Assessment and Control, aqueous ozone has been effectively used to disinfect drinking water, cooling towers and for waste water treatment. When used to treat water, ozone concentrations less than 1 part per million are reported as being effective. Regardless of its effectiveness for controlling bacteria and other organisms in water, the ACGIH publication states that aqueous ozone is "subject to rapid degradation and certainly is not recommended for use on visible fungal growth."

Ozone in its gaseous phase was studied and found ineffective for use on surface contaminants as early as 1942. in a 1997 study performed by Karin Foarde, et al, the ability of ozone to decontaminate fungi on a variety of building materials exposed to ozone at 9 parts per million (ppm) for a 23 hour exposure, found ozone to be ineffective. To put this amount of ozone in perspective, 9 ppm is 90 times the present OSHA Permissible Exposure Limit (PEL) of 0.1 ppm The 9 ppm used is this study is almost twice the amount presently determined by NIOSH to be Immediately Dangerous to Life and Health (IDLH), 5 ppm.

According to the United States EPA's Mold Remediation in Schools and Commercial Buildings, "The purpose of mold remediation is to remove the mold to prevent human exposure and damage to building materials and furnishings. It is necessary to clean up mold contamination, not just to kill the mold. Dead mold is still allergenic, and some dead molds are potentially toxic."

The New York City Department of Health's Guidelines on the Assessment and Remediation of Fungi in Indoor Environments states: "The use of gaseous, vapor-phase, or aerosolized biocides for remedial purposes is not recommended. The use of biocides in this manner can pose health concerns for people in occupied spaces of the building and for people returning to treated space if used improperly. Furthermore, the effectiveness of these treatments is unproven and does not address the possible health concerns from the presence of the remaining non-viable mold."

The IICRC S520 Standard and Reference Guide for Professional Mold Remediation agrees with the EPA and NYC documents when it states, "The use of treatments, such as encapsulants, sealants, ozone or ultraviolet (UV) light as a substitute for removal and detailed cleaning is generally not recommended."

It is important to remember that ozone has a strong oxidizing reaction on rubber and other materials. As a result it may be responsible for electrical safety hazards, since it can destroy some types of electrical insulation and damage other materials. Other studies have demonstrated that ozone can actually increase the levels of formaldehyde and other chemicals when used in buildings. Ozone has been shown to increase submicron particles and adversely react with many compounds and artwork.

In spite of the strong evidence that ozone is not appropriate for fungal remediation activities, as described in the IICRC S520 Mold Remediation Standard, some publications continue to suggest it be used for this purpose. A recent study concluded that for Penicillium citrinum and other organisms "ozone should be highly effective and provide a reliable safety factor in treating microorganism contaminated surfaces." After reviewing the article, Eugene Cole, DrPH. and professor of Environmental Health at Brigham Young University, stated that "the study was conducted by exposing mold to ozone on agar plates where the mold was growing. It is not surprising the mold was killed, since the agar acts like an aqueous environment. One should not expect ozone to kill mold on building materials, and even if it did the dead microbial residue would continue to pose a potential allergic or toxicogenic hazard if left in place."

It should be noted that the levels of ozone tested in the study ranged from 8 to 16 parts per million. As noted above, this level far exceeds the OSHA PEL of 0.1 ppm for an 8 hour exposure. Even if ozone was effective in killing mold on building materials, it is considered unlikely that ozone concentrations in buildings could be controlled to achieve such concentrations.

So, is there ever a time when the use of ozone might be appropriate in mold remediation? According to the IICRC S520, "With heavy mold odors, a deodorization process, such as confined use of ozone, may be desirable prior to and/or following laundering or dry cleaning."

—Jim Holland

The Use of Chlorine Dioxide: I recently read that Chlorine Dioxide was used to remediate mold in a building. Why is this process is not mentioned the S520 Mold Remediation Standard?

Chlorine Dioxide is a biocide that can be used as a gas or as a liquid. In the past, it was created by mixing either sodium chlorite or stabilized chlorine dioxide with another "reactive" chemical, generally an acid such as citric or lactic acid. According to one source, Chlorine dioxide is generated for smaller applications by the reaction of sodium chlorite with chlorine, either through gaseous chlorination or the reaction of sodium hypochlorite with hydrochloric acid. The result is chlorine dioxide in a liquid or gas and they smell like chlorine bleach.

The Environmental Protection Agency (EPA) first registered chlorine dioxide gas, as an antimicrobial pesticide, in the 1980s. Chlorine dioxide gas is registered for sterilizing manufacturing and laboratory equipment, environmental surfaces, tools, and clean rooms. Types of antimicrobial products have traditionally included sanitizers, disinfectants, and sterilants.

A "sanitizer" is a substance that significantly reduces the bacterial population in the inanimate environment, but does not destroy or eliminate all bacteria or other microorganisms.

A "disinfectant" is a substance that destroys or eliminates a specific species of infectious or other public health microorganism, but not necessarily bacterial spores, in the inanimate environment.

A "sterilant" is a substance that destroys or eliminates all forms of microbial life in the inanimate environment, including all forms of vegetative bacteria, bacterial spores, fungi, and fungal spores.

Since Chlorine dioxide is registered as a pesticide, it needs to be used consistent with its label and any other restrictions that may be applicable. The permissible exposure limit (PEL) of .1 ppm and a short term exposure limit (STEL) of .3 ppm. When it was used for the emergency treatment of Anthrax, it required an emergency exemption from the EPA.

The following is from the EPA website:

FIFRA Section 18 Emergency Exemptions and Anthrax
Under Section 18 of FIFRA, EPA "may exempt any federal or state agency from any provision of this Act if the Administrator determines that emergency conditions exist which require such exemption." Normally, a federal or state agency submits an application for a FIFRA exemption to EPA for review and approval. If EPA approves the request, it issues either a specific or a public health exemption, as appropriate. However, if the emergency is of such urgency that the federal or state agency does not have enough time to submit an application for exemption and wait for EPA's approval, then the federal or state agency may issue a crisis exemption, which is effective for 15 days. In order for the crisis exemption to be extended beyond 15 days, the federal or state agency must submit an application for exemption to EPA.

To handle all anthrax contamination cases as quickly as possible, the Agency has decided to issue all crisis exemptions itself. To obtain a crisis exemption from EPA for the unregistered use of a pesticide against anthrax, a state or federal agency must submit a written request describing the antimicrobial product(s) to be used; how, when and where they will be used; the data demonstrating efficacy of the product for the intended purpose; and how human health and safety will be protected. Prior to issuing the exemption, EPA will perform a multi-disciplinary risk assessment of the requested use, relying on data that they have supplied for the pesticide.

If, during this review, EPA notes any adverse human health or environmental concerns, EPA may deny the exemption request. If, however, EPA believes that the proposed use of an antimicrobial product will be effective and will protect human health and the environment, EPA will issue a crisis exemption. Moreover, if EPA determines that use of the product is needed beyond the 15-day use period, EPA will complete an application for a public health exemption on behalf of the requesting entity, which allows the crisis exemption to continue in effect until it is either withdrawn or EPA issues a public health exemption.

Determination of Safety and Efficacy for Crisis Exemptions for Chlorine Dioxide
EPA has reviewed data related to safety and effectiveness before allowing an emergency exemption for liquid and gaseous chlorine dioxide to be used specifically for anthrax decontamination. Available published data suggest that liquid and gaseous chlorine dioxide will reduce bacterial spore populations under specific conditions including concentration, pH, and contact time.

Based on this review, EPA issued crisis exemptions for the limited sale, distribution, and use of liquid and gaseous chlorine dioxide against anthrax.

Typically Chlorine dioxide gas is generated on site and is released into a sealed treatment area where it remains for several hours before being removed. After the treatment is completed, the chlorine dioxide gas is neutralized with sodium bisulfite. The treatment may leave a fine residue, but it is not toxic.

As you can see, the use of Chlorine Dioxide is not as simple and uncomplicated as the application of a liquid biocide. There are worker exposure issues and cleanup issues. The Institute of Inspection, Cleaning and Restoration Certification (IICRC) S520 Standard and Reference Guide for Professional Mold Remediation does not recommend the use of Chlorine Dioxide specifically. However, S520 does make the following statement under the Not Recommended and Antimicrobial Pesticide Products subheadings:

Limitations of Use
The use of antimicrobial pesticides has a number of limitations. One limitation can be a lack of clear, detailed label application directions and adequate information on hazards and risks. If used, such products must be used with full knowledge of their limitations and capabilities, in strict accordance with manufacturer’s directions and all regulatory requirements, and only with client informed consent. Specifically, the use of antimicrobial pesticide products requires that a mold remediator:

comply with training, safety, use and licensing requirements;
train and supervise all employees handling antimicrobial products;
only apply products that have been evaluated and registered by appropriate governmental agencies;
apply products strictly in accordance with label directions;
discuss potential risks and benefits with the customer, and obtain a written informed consent with the customer’s signature before application;
document all product application details;
refrain from making statements or representations to the customer beyond those stated on the product label or in the efficacy claims made by the product and approved by the applicable government agency, and
when in doubt consult the appropriate state, provincial, or federal agency.

The S520 makes the following statement in the Remediation Work Procedures section of the Reference Guide:

Physically removing mold growth and spores is the guiding principle for mold remediation. Biocide application is discouraged and is not considered effective for mold remediation.……. Misapplication of biocides is a federal violation under the U.S. Federal Insecticide, Fungicide, Rodenticide Act (FIFRA). Killing microorganisms usually does not destroy their antigenic or toxigenic properties

The American Conference of Governmental Industrial Hygienists (ACGIH) in their publication Bioaerosols: Assessment and Control makes the following comments:

16.2 Biocide use should not be considered if careful and controlled removal of contaminated material is sufficient to address a problem.

16.2.3 Effective remediation of water-damaged or microbially contaminated buildings involves (a) the use of appropriate techniques to promote rapid drying, and (b) complete removal of contaminated materials rather than the application of biocides.

—Jim Holland

Biocides or Antimicrobials: Why is it that people sometimes refer to the chemicals that are used to kill mold and bacteria as biocides and at other time antimicrobials? I thought that there was a difference between the two?

The IICRC S500 Standard and Reference Guide for Professional Water Damage Restoration currently refers to those chemicals that are used to kill micro-organisms as biocides and those that retard or suppress growth as antimicrobials. Biocides are sometimes referred to as bactericides or fungicides when they are designed to kill bacteria and fungi respectively. In addition, antimicrobials are sometimes referred to as bacteriostats or fungistats when they are designed to inhibit growth of bacteria or fungi. If you break down the term biocide into its prefix and suffix, you come up with bio-, which means life and -cide, which means kill. Therefore, they are life killers. The suffix -stat means stasis or static. Often the products referred to as fungistats only inhibit microbial growth and do not necessarily kill fungi. They maintain a static environment.

"Bacteriostatic agent: chemical agent that suppresses or retards bacterial growth on direct contact with the treated material.

Fungistatic agent: chemical agent that suppresses or retards fungal growth on direct contact with the treated material." (Table 16.1)

Another well respected publication has similar definitions as the ACGIH publication, Disinfection, Sterilization, and Preservation by Seymour S. Block. While this book does use similar terms, it also refers to biocides as antimicrobial in several instances. A biocide is defined as "a substance that kills all living organisms, pathogenic or nonpathogenic." A bacteriostat is defined as "an agent, usually chemical, that prevents the growth of bacteria but does not necessarily kill them or their spores." Finally, an antimicrobial agent is defined as "any agent that kills or suppresses the growth of microorganisms." This last definition is somewhat consistent with the way that the Environmental Protection Agency (EPA) refers to biocides and antimicrobials. Interestingly, the EPA also refers to both biocides and antimicrobials as pesticides. On the EPA website under the heading "What are Antimicrobial Pesticides?" it states "Antimicrobial pesticides are substances or mixtures of substances used to destroy or suppress the growth of harmful microorganisms whether bacteria, viruses, or fungi on inanimate objects and surfaces" (http://www.epa.gov/oppad001/ad_info.htm). In some states you might be required to have a pest control applicator's license in order to apply these products legally in your customers' homes.

There is currently an effort to change the way that we, as an industry, refer to these chemicals. You may see that there is a change in the IICRC standards to using the EPA terminology. While I understand the desire to change to the EPA terminology, I do not look forward to these terms being substituted into the standards. They are more confusing to the reader than the terms that we have used until now. If there is a change to the new terminology, we will be referring to quaternary ammonium chloride (quats) as a biocide and as an antimicrobial or pesticide. On the other hand, there are those that will argue that the change to the EPA terminology will make it more consistent and ultimately less confusing. Time will tell.

Now, to answer your question, either term can be used. Whenever you read a document, look for any definitions that are provided in the text. Always read the document with these definitions in mind. If there are no definitions look for the function of the chemical to determine its class.

—Jim Holland