Biological Risk Engineering Handbook: Infection Control and Decontamination - Chapter 12 pot

© 2003 BY CRC PRESS LLC
CHAPTER 12
Biocides
Martha J. Boss and Dennis W. Day
CONTENTS
12.1 Non-Public Health Products
12.2 Public Health Products
12.2.1 Sterilizers (Sporicides)
12.2.2 Disinfectants
12.3 Antiseptics and Germicides
12.4 Sanitizers
12.4.1 Food-Contact Sanitizers
12.4.2 Non-Food-Contact Sanitizers
12.5 Decontamination Methods and Biocides
12.6 Acids and Alkalizers
12.6.1 Acids
12.6.2 Alkalizers
12.7 Alcohols
12.8 Chloramines
12.9 Ammonia and Quaternary Ammonia
12.10 Dyes
12.10.1 Formaldehyde
12.10.2 Ethylene Oxide
12.10.3 Beta-Propriolactone
12.10.4 Glutaraldehyde
12.11 Halogens
12.11.1 Iodine
12.11.2 Iodophors
12.11.3 Chlorine
12.12 Heavy Metals
12.13 Oxidizers

12.13.1 Ozone
12.14 Phenols
12.15 Soaps and Synthetic Detergents
12.15.1 Anionic Detergents
12.15.2 Cationic Detergents
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12.15.3 Nonionic Detergents
12.16 Irradiation or Ultraviolet Light
12.17 Desiccants
12.18 Low Temperatures
12.19 Equipment Decontamination or Disposal
References and Resources
This chapter discusses the rationale for choosing or specifying various biocides, the known
additional risks imposed through the use of biocides, the testing required to prove biocide claims,
and the limitations of Material Safety Data Sheets (MSDS) in providing hazard communication
information. Antimicrobial agents 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. Antimicrobial products contain about 300 different active ingredients and are
marketed in several formulations: sprays, liquids, concentrated powders, and gases. More than 8000
antimicrobial products are currently registered with the U.S. Environmental Protection Agency
(EPA) and sold in the marketplace. Nearly 50% of antimicrobial products are registered to control
infectious microorganisms in hospitals and other healthcare environments. However, public health
antimicrobial products tend to be low-volume products and thus constitute less than 5% of the
estimated total market for antimicrobial products. Antimicrobial products are divided into two
categories based on the type of microbial pest against which the product works.
12.1 NON-PUBLIC HEALTH PRODUCTS
Non-public health products are used to control the growth of algae, odor-causing bacteria,
bacteria that cause spoilage, deterioration or fouling of materials, and microorganisms infectious
only to animals. This general category includes products used in cooling towers, jet fuel, paints,
and treatments for textile and paper products.

12.2 PUBLIC HEALTH PRODUCTS
Public health products are intended to control microorganisms infectious to humans in any
inanimate environment. The more commonly used public health antimicrobial products include the
following:
• Bactericidals, to kill bacteria
• Bactericides, to kill bacteria
• Bacteriostats, to inhibit the growth of bacterial cells
• Cidal agents, to kill cells
• Fungicides, to kill fungi
• Static agents, to inhibit the growth of cells (without killing them)
12.2.1 Sterilizers (Sporicides)
Sterilization is complete destruction or elimination of all viable organisms (in or on an object
being sterilized). An object is either completely sterile or not sterile, nothing in between.
Sterilization is used to destroy or eliminate all forms of microbial life, including fungi, viruses,
and all forms of bacteria and their spores. Spores are considered to be the most difficult form
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of microorganism to destroy; therefore, the EPA considers the term sporicide to be synonymous
with sterilizer. Sterilization is critical to infection control and is widely used in hospitals on
medical and surgical instruments and equipment. Gaseous and dry-heat sterilizers are used
primarily for sterilization of medical instruments. Liquid sterilants are primarily used for delicate
instruments that cannot withstand high temperatures and gases. Chemical sterilizers include low-
temperature gas (ethylene oxide) and liquid chemical sterilants. Following are features of the
heat sterilization methods.
12.2.1.1 Heat
For heat sterilization, consider the type of heat, the application interval, and the temperature.
Endospores of bacteria are considered the most thermoduric of all cells. The destruction of test or
indicator endospores guarantees sterility.
12.2.1.2 Incineration (> 500°F)
Incineration literally burns organisms from equipment or from the interior of vessels. Nonporous
and nonflammable objects that can survive the heat levels needed to destroy contained organisms

can be incinerated. Incineration can also be used to destroy organisms in wastes, in that the integrity
of the remaining materials for future use is not an issue.
12.2.1.3 Water Boiling (100°C)
Boiling water at 100°C for 30 minutes can be effective in killing microbial pathogens and
vegetative forms of bacteria. To kill endospores, and therefore sterilize the solution, very long or
intermittent boiling is required. Intermittent boiling is defined as boiling for three 30-minute
intervals, followed by periods of cooling.
12.2.1.4 Autoclaving (121°C)
Autoclaving is another name for pressure cooking. A temperature of 121°C for 15 minutes at
a pressure of 15 lb/in.
2
sterilizes. The effective temperature (121°C) must be maintained for the
full 15 minutes. Some materials will be destroyed at these temperatures through melting.

12.2.1.5 Dry Heat/Hot-Air Oven (160 and 170°C)
These ovens maintain a temperature of 160°C for 2 hours or 170°C for 1 hour. The ovens can
be used for objects that will not melt and must remain dry.
12.2.1.6 Pasteurization
Pasteurization is the use of mild heat to reduce the number of microorganisms in a product
or food. In the case of pasteurization of milk, the time and temperature depend on killing potential
pathogens that are transmitted in milk (e.g., Staphylococcus, Streptococcus, Brucella abortus,
and Mycobacterium tuberculosis). For pasteurization of milk, the following methods can be used:
• Batch method: 63°C for 30 minutes kills most vegetative bacterial cells, including pathogens such
as Streptococcus, Staphylococcus, and Mycobacterium tuberculosis.
• Flash method: 71°C for 15 seconds has an effect on bacterial cells similar to the batch method;
for milk, this method is more conducive to industry
and has fewer undesirable effects on quality
or taste.
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12.2.2 Disinfectants

Disinfectants kill microorganisms, but not necessarily their spores, and are not safe for appli-
cation to living tissues. They are used on hard inanimate surfaces and objects to destroy or
irreversibly inactivate infectious fungi and bacteria but not spores. Examples include chlorine,
hypochlorites, chlorine compounds, lye, copper sulfate, and quaternary ammonium compounds.
Disinfectant products are divided into two major types: hospital and general use.
12.2.2.1 Hospital Disinfectants
Hospital disinfectants are the most critical to infection control and are used on medical and
dental instruments, floors, walls, bed linens, toilet seats, and other surfaces.
12.2.2.2 General Use Disinfectants
General use disinfectants are the major type of products used in households, swimming pools,
and water purifiers. Disinfectants and antiseptics are distinguished on the basis of whether they are
safe for application to mucous membranes, and safety often depends on the concentration of the
compound. For example, sodium hypochlorite (chlorine), as added to water, is safe for drinking,
but Clorox
®
, an excellent disinfectant, is not safe to drink.
12.3 ANTISEPTICS AND GERMICIDES
Antiseptics and germicides are used to prevent infection and decay by inhibiting the growth of
microorganisms. Because these products are used in or on living humans or animals, they are
considered drugs and are thus approved and regulated by the Food and Drug Administration (FDA).
Antimicrobial pesticides, such as disinfectants and sanitizers, are pesticides that are intended to:
• Disinfect, sanitize, reduce, or mitigate growth or development of microbiological organisms
• Protect inanimate objects, such as floors and walls, cabinets, toilets, industrial processes or systems,
paints, metalworking fluids, wood supports, surfaces water, or other chemical substances
These products protect users from contamination, fouling, or deterioration caused by bacteria,
viruses, fungi, protozoa, algae, or slime. Antimicrobial pesticides, as a regulatory category, do not
include certain pesticides intended for food use but do encompass pesticides with a wide array of
other uses. Antimicrobials are especially important because many are public health pesticides. They
help to control microorganisms (viruses, bacteria, and other microorganisms) that can cause human
disease. Antimicrobial public health pesticides are used as disinfectants in medical settings. Proper

use of these disinfectants is an important part of infection control activities employed by hospitals
and other medical establishments.
Disinfectants and sanitizers contain toxic substances. The ability of chemicals in other household
products used for cleaning to cause health effects varies greatly, from those with no known health
effect to those that are highly toxic. Read and follow label instructions carefully, and provide fresh
air by opening windows and doors. If it is safe for you to use electricity and the home is dry, use
fans both during and after the use of disinfecting, cleaning, and sanitizing products. Be careful
about mixing household cleaners and disinfectants together (check labels for cautions on this).
Mixing certain types of products can produce toxic fumes and result in injury and even death.
Antiseptics are microbiocidal agents harmless enough to be applied to the skin and mucous
membrane, but they should not be taken internally. Examples include mercurials, silver nitrate,
iodine solution, alcohols, and detergents.
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12.4 SANITIZERS
Used to reduce, but not necessarily eliminate, microorganisms from the inanimate environment
to levels considered safe as determined by public health codes or regulations.
12.4.1 Food-Contact Sanitizers
Food-contact sanitizers include rinses for such surfaces as dishes and cooking utensils and for
equipment and utensils found in dairies, food-processing plants, and eating and drinking establish
-
ments. These products are important because they are used at sites where food products are stored
and consumed.
12.4.2 Non-Food-Contact Sanitizers
Non-food-contact surface sanitizers include carpet sanitizers, air sanitizers, laundry additives,
and in-tank toilet bowl sanitizers.
12.5 DECONTAMINATION METHODS AND BIOCIDES
Decontamination methods may be very similar to those used to abate asbestos or lead. The
main difference is the use of biocides, which are chemicals designed to kill life. Thus, at concen
-
trated levels, biocides are a danger to workers. Manufacturers’ instructions must be carefully

followed. When researching which biocides to use and the concentrations required, the following
should be considered:
• Type of biological contamination: Does the manufacturer have data showing that the product is
effective against the biological contaminants at the current contamination level? Dwell time
required after application of the biocide should be calculated in terms of biocide effectiveness.
• Presence of electrical wiring or ventilation equipment that could be corroded by biocides
• Flammability hazards posed by the biocides and their application methods
• General building ventilation, workplace zoning, and level of occupancy of the building
• Ability to isolate or shut down the heating, ventilation, and air conditioning (HVAC) system
• Usage in false plenums, ductwork, flexible ductwork, horizontal plenums, and ventilation hoods
• Usage in furnace, boiler, or other combustion chamber areas
• Usage on condensers, face and bypass systems, and evaporative coils
• Usage in cooling towers, sumps, liquid-filled plumbing lines and vessels, misters
• Usage in humidifiers, swamp coolers, and sprinkler systems
• Slip, trip, and fall potential when used on flooring or polyethylene sheeting
• Dermal hazard potential if personal protective equipment (PPE) is breached
• Respiratory hazards for the chosen application methods
• Waste disposal requirements
These and other questions regarding biocides and decontamination methods must be approached
on a site-specific basis. Issues regarding potential adverse effects on carpets, porous materials,
heirlooms, antique finishes, and other real property not slated for disposal must also be considered.
Biocides come in several forms:
• Acids or bases that are pH altering
• Chlorines, bromines, or iodines
• Chlorine dioxide
• Hydrogen peroxide
• Hypochlorite granules
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• Alcohols
• Phenols such as the active ingredients in Lysol


• Sulfur compounds
• Quaternary ammonia
• Stabilized chemical mixes
• Ozone gases
Soaps have limited biocide properties and function primarily to remove biological contamination
from surfaces. Some liquid soaps have added biocides to enhance their bacterial biocide effect. Bar
soaps should not be used on decontamination sites, as without sufficient drying the bar and
surrounding liquids may harbor biological contaminants. Ozone gas treatments used alone or in
combination with ultraviolet light treatment have shown success in eliminating airborne spores.
These treatments, however, must be repeated several times to cover all spore-release cycles follow
-
ing initial decontamination events.
Material Safety Data Sheets for biocides may discuss hazards based on the assumption that the
biocides will be used for surface applications only. Manufacturers should be consulted whenever
fogging, concentrated soaking applications, high-pressure delivery systems, or usage within confined
areas is anticipated. Steam cleaning without the use of biocide washes or rinses is usually not effective
and may make the situation worse. The core of the stream is very hot and perhaps produces steam,
but the peripheries of the core often do not retain sufficient heat to kill biological contaminants.
Dry and wet vacuuming, if used in a cleaning cycle, may aerosolize additional biological
fragments, spores, and particulates to which biological contaminant are attached. Thus, vacuuming
and sweeping may require additional personal and area protection for workers and building inhab
-
itants. In general, dry removal without prior treatment of areas with biocides should be carefully
evaluated in terms of increased hazards.
The choice of biological decontamination methods must be determined by an Occupational
Safety and Health Administration (OSHA)-competent person and should be reflected in contract
documents and resulting plans.
Due to their spent biocide content, biocides and materials treated with biocides may be considered
hazardous wastes. During the development of MSDS, manufacturers are required to determine disposal

options for spent chemical, but materials laced with the chemical are not included in MSDS devel
-
opment. In determining appropriate disposal and labeling requirements, the following general regu-
latory requirements should be considered: 29 CFR 1910.1200 (Hazard Communication) and equivalent
requirements in 29 CFR 1926; the Resource Conservation and Recovery Act (RCRA), in regard to
storage, treatment, and disposal of wastes; and Department of Transportation (DOT) requirements for
labeling, marking, placarding, and transportation protocols on public byways.
12.6 ACIDS AND ALKALIZERS
Acids and alkalizers cause changes in the microenvironment of the microbes.
12.6.1 Acids
If the microenvironment is maintained at about pH 3, organisms begin to die off. The longer
this lower pH is maintained, the greater the die off. Acids are used in food preservation techniques.
12.6.2 Alkalizers
Alkalizers work against Gram-positive cocci, rods, spore-formers, and some viruses. Mycobac-
terium species are resistant to alkali
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12.7 ALCOHOLS
Alcohols are effective killers of vegetative bacteria and fungi but are not effective against
endospores and most viruses. They are used to enhance the effectiveness of other chemical agents
and work by denaturing proteins and dissolving lipids. The effectiveness of various alcohols
increases with increasing molecular weight; unfortunately, their negative impact on skin also
increases. Ethanol (50–70%) and isopropanol (50–70%) denature proteins and solubilize lipids and
are used as antiseptics on skin.
12.8 CHLORAMINES
Chloramines are produced by, and ultimately are a combination of, chlorine and ammonia.
Chloramines are slow to volatilize, release the chlorine over long periods of time, are effective in
contact with organic matter, and are used in root canal surgery and for general wound disinfection.
Halazone is an example of a chloramine used for emergency disinfection of water. Chloramine is
used in the treatment of public water supplies to reduce tastes and odors, the by-products of
disinfection such as trihalomethanes (THMs), and the level of THMs in the water. The principal

disadvantages of chloramines are that they are far weaker and slower acting disinfectants than
chlorine and are especially weak for inactivating certain viruses.
When chloramine is used as the principal disinfectant, ammonia is added at a point downstream
from the initial chlorine application so that microorganisms, including viruses, will be exposed to
the free chlorine for a short period before the chloramine is formed. Hospitals and kidney dialysis
centers must be alerted when chloramines are used for water supply disinfection. Cases of chloram
-
ine-induced hemolytic anemia in patients have been reported when their dialysis water was not
appropriately treated. Otherwise, no ill effects associated with the ingestion of chloraminated
drinking water are documented. Chloramines can be removed from water with very low flow rates
(5 to 10 minutes contact time) through shell-base activated carbon, followed by mineral zeolite
media for residual ammonia adsorption.
12.9 AMMONIA AND QUATERNARY AMMONIA
Ammonia and quaternary ammonia are detergents (quaternary ammonium compounds) that
disrupt cell membranes and are used as skin antiseptics and disinfectants.
12.10 DYES
Dyes are used primarily in selective and differential media and can be used intravenously and
as pills or applied to the skin in liquid form. Some dyes may be strong mutagenic agents, and the
actions of some are unclear. When used as gaseous chemosterilizers, these disinfectant aerosol
particles should be between 1 and 5 µm in size to be most effective:
12.10.1 Formaldehyde
Formaldehyde (8%), or formalin (40%), reacts with NH
2
, SH, and COOH groups to disinfect
by killing endospores. Formaldehyde is toxic to humans, works best in dry environment (better
penetration), and crystallizes at room temperature.
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12.10.2 Ethylene Oxide
Ethylene oxide is volatile, flammable, and offers good penetration. Ethylene oxide gas is an
alkylating agent used to sterilize heat-sensitive objects such as rubber and plastics.

12.10.3 Beta-Propriolactone
Beta-propriolactone is nonflammable, and is more antimicrobial and less penetrating than
ethylene oxide.

12.10.4 Glutaraldehyde
Glutaraldehyde is effective at room temperature, and its microbial activity increases with heat.
It is effective against certain viruses, endospores, and Mycobacterium species. It may irritate skin
or eyes. Examples of glutaraldehyde include Sonacide

, Cidex

, and Metracide

.
12.11 HALOGENS
Halogens include iodine, chlorine, bromine, and fluorine. The disinfectant usually recommended
for mold removal is a solution of one part bleach to two parts water. Commercial disinfectants are
also available through janitorial supply stores. Use a household or garden sprayer and spray all
surfaces that have been touched by flood water or have been soaked by water from some other
source. Use a brush or broom to force the solution into crevices.
12.11.1 Iodine
Tincture of iodine (2% I
2
in 70% alcohol) inactivates proteins and is used as an antiseptic on
skin. Iodine is one of the oldest (300 to 400 years) and most effective germicidal agents. It is a
broad-spectrum bactericide and a good fungicide with some viricidal action. It will kill spores and
is an excellent disinfectant that is effective against protozoa (amebas). It is only slightly soluble in
water; iodine is available as a tincture dissolved in alcohol.
Problems arise when the alcohol
evaporates and the concentration of iodine increases, which can cause burning of skin.

12.11.2 Iodophors
Iodophors are combinations of iodine and organic molecules (hydrocarbons). Iodophors work
by inhibiting enzyme action and are more effective than iodine. They are nonirritating, good
surfactants, and nonstaining.
12.11.3 Chlorine
Chlorine (Cl
2
) gas forms hypochlorous acid (HClO), a strong oxidizing agent, and is used to
disinfect drinking water and as a general disinfectant. Chlorine is used as a gas dissolved in water
or in combination with other chemicals. The chlorine mode of operation is not completely under
-
stood but appears to be a strong oxidizing agent as result of the following reaction:
Cl
2
+ H
2
O → HCl + HClO → HCl + [O]
Hypochlorites are used domestically and industrially for disinfection. Hypochlorites were first
advocated by Semmelweiss (1846–1848) to reduce incidence of childbed fever in hospitals, and
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they have a broad spectrum of kill. NaOCl (sodium hypochlorite) is the active agent in Clorox

.
Chlorine is a universal disinfectant that is active against all microorganisms, including bacterial
spores. Potential applications for chlorine as a disinfectant include:
• Work surfaces
•Glassware
• Fixed or portable equipment and cages
• Liquids treated for discard
• Before and after vivarium entry, as a footbath

Many active chlorine compounds are available at various strengths; however, the most widely
used for chemical disinfection is sodium hypochlorite. Household or laundry bleach is a solution
of 5.25% (or 52,500 ppm) sodium hypochlorite. Note that a 10% or 1:10 dilution of bleach will
result in a 0.525% or 5250-ppm solution of chlorine. The Centers for Disease Control and Prevention
(CDC) recommends 500 ppm (1:100 dilution of household bleach) to 5000 ppm (1:10 dilution of
bleach), depending on the amount of organic material present, to inactivate the human immunode
-
ficiency virus (HIV). The strength of chlorine to be used for disinfection must be clearly indicated
when described in standard operating procedures.
Chlorine solutions will gradually lose strength, so fresh solutions must be prepared frequently.
Diluted solutions should be replaced after 24 hours. The stability of chlorine in solution is greatly
affected by the following factors:
• Chlorine concentration
• Presence and concentration of catalysts such as copper or nickel
• pH of the solution
• Temperature of the solution
• Presence of organic material
• Ultraviolet irradiation
The chlorine solution should have the following characteristics for maximum stability:
• Low chlorine concentration
• Absence or low content of catalysts such as nickel or copper
• High alkalinity
• Low temperature
• Absence of organic materials
Chlorine should be shielded from ultraviolet light by storage in the dark in closed containers.
The following factors may or may not affect chlorine biocidal activity:
• pH — Chlorine is more effective at a lower pH.
• Temperature — An increase in temperature produces an increase in bactericidal activity.
• Concentration — A fourfold increase of chlorine will result in a 50% reduction in killing time,
and a twofold increase results in a 30% reduction in killing time.

• Organic material — Organic material will consume available chlorine. If the organic material
contains proteins, the reaction with chlorine will form chloramines that will have some antibacterial
activity. Loss due to organic materials is more significant if minute amounts of chlorine are used.
Footbaths are frequently contaminated with organic material and may require more frequent
changing than the 24 hours previously stated.
• Hardness — Hardness of the water does not have a slowing effect on the antibacterial action of
sodium hypochlorite.
• Addition of ammonia or amino compounds — Addition of ammonia and nitrogen compounds will
slow the bactericidal action of chlorine.
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Other available active chlorine sources include liquid chlorine, chlorine dioxide, inorganic chloram-
ines, organic chloramines, and halazone.
Chlorine combines with protein and rapidly decreases in concentration when protein is present.
This property gives rise to swimming pool odor which is often mistaken for the odor of chlorine.
In actuality, that characteristic swimming pool odor indicates that the chlorine in the water has
combined with organic contaminants and is off-gassing from the pool water. The organic source
may be contamination in the pool (e.g., perspiration, urine, feces). Other natural non-protein
materials and plastics and cationic detergents may also inactivate chlorine.
Chlorine is a strong oxidizing agent that is corrosive to metals and should not be used on the
metal parts of machines that are subject to stress when in use. Do not autoclave chlorine solutions
or materials treated with them, as the residual chlorine can vaporize resulting in an inhalation
hazard. Do not use chlorine in combination with ammonia, acetylene, butadiene, butane, methane,
propane or other petroleum gases, hydrogen, sodium carbide, benzene, finely divided metals, or
turpentine. Chlorine may cause irritation to the eyes, skin, and lungs. Wear safety goggles, rubber
gloves, aprons, or other protective clothing when handling undiluted solutions.
12.12 HEAVY METALS
Heavy metals are the most ancient of antiseptics and disinfectants. Heavy metals were used by
Egyptians, in the form of gold ointments and dust, and were often buried with the corpse or
mummies to provide salves and ointments in the afterlife. Heavy metals have an oligodynamic (all
encompassing) action and are extremely effective. They work because of the strong affinity of the

metals to proteins. Metallic ions bind and adhere to the sulfhydryl groups in proteins, and enzymatic
bindings are created. Stronger concentrations act as protein precipitants. Low concentrations have
a subtle interference on the metabolism of the cell. Examples of heavy metal usage as disinfectants
include the use of copper for ionizing water and to control algae. DaVinci and others added gold
dust to ointments for wounds.
Mercuric chloride inactivates proteins by reacting with sulfide groups and is used as a disin-
fectant, although it occasionally is also used as an antiseptic on skin. Mercurials (inorganic mercury
compounds) have a long history, with their heyday occurring during World War I. Mercurials were
replaced by organic mercury compounds such as mercurochrome, methiolate, and metaphen. These
compounds were used as skin antiseptics but their effects are reversed when they are washed off.
Due to the toxic effects of mercury, these compounds are no longer recommended for first aid or
skin disinfection.
Silver nitrate (AgNO
3
) precipitates proteins and is used as a general antiseptic and in the eyes
of newborns. Silver, as a 1% silver nitrate solution (Argyrol), has been used as an antiseptic and
in the eyes of newborn, although this practice has been largely replaced by the use of antibiotics.
Zinc is used in combination with chlorine compounds as a mouthwash and in other combinations
is an effective fungicide. Organometallics (organically activated metals such as heavy metals or
organic radicals such as alcohol) are effective against Gram-positive cocci, diphtheroids, spore-
forming rods, tuberculosis, and similar organisms and may be effective against viruses. They are
extremely effective against mycoses and have virtually no effectiveness against Gram-negative rods.
Tributyltin is an example of an organometallic that also has deodorizing qualities.
12.13 OXIDIZERS
Oxidizers supply boundless oxygen. In combination with mercurials, oxidizers have been used
in wound cleaning. Examples include H
2
O
2
(hydrogen peroxide), KMnO

4
(potassium permangan-
ate), and zinc peroxide.
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12.13.1 Ozone
Ozone generators sold as air cleaners intentionally produce the gas ozone. Ozone is a molecule
composed of three atoms of oxygen. Two atoms of oxygen form the basic oxygen molecule — the
oxygen we breathe that is essential to life. The third oxygen atom can detach from the ozone
molecule and reattach to molecules of other substances, thereby altering their chemical composition.
Ozone is a toxic gas with vastly different chemical and toxicological properties from oxygen (see
Table 12.1). The same chemical properties that allow high concentrations of ozone to react with
organic material outside the body give it the ability to react with similar organic materials that
make up the body, with potentially harmful health consequences. Relatively low amounts can cause
chest pain, coughing, shortness of breath, and, throat irritation. Ozone may also worsen chronic
respiratory diseases such as asthma and compromise the ability of the body to fight respiratory
infections. Whether in its pure form or mixed with other chemicals, ozone can be harmful to health.
When inhaled, ozone can damage the lungs.
People vary widely in their susceptibility to ozone. Healthy people, as well as those with
respiratory difficulty, can experience breathing problems when exposed to ozone. Exercise during
exposure to ozone causes a greater amount of ozone to be inhaled and increases the risk of harmful
respiratory effects. Recovery from the harmful effects can occur following short-term exposure to
low levels of ozone, but health effects may become more damaging and recovery less certain at
higher levels or from longer exposures. Several federal agencies have established health standards
or recommendations to limit human exposure to ozone. No agency of the federal government has
approved ozone generators for use in occupied
spaces.
Table 12.1 Ozone Health Effects and Standards
Health Effects Risk Factors Health Standards
Potential risk of experiencing: Factors expected to
increase risk and severity

of health effects are:
The Food and Drug
Administration (FDA)
requires ozone output of
indoor medical devices to
be no more than 0.05
ppm.
Decreases in lung function Increase in ozone air
concentration
The Occupational Safety
and Health Administration
(OSHA) requires that
workers not be exposed to
an average concentration
of more than 0.10 ppm for
8 hours.
Aggravation of asthma Greater duration of
exposure for some health
effects
The National Institute of
Occupational Safety and
Health (NIOSH)
recommends an upper
limit of 0.10 ppm, not to be
exceeded at any time.
Throat irritation and cough
Chest pain and shortness of breath Activities that raise the
breathing rate (e.g.,
exercise)
The Environmental

Protection Agency’s (EPA)
National Ambient Air
Quality Standard for
ozone is a maximum 8-
hour average outdoor
concentration of 0.08
ppm.
Inflammation of lung tissue Certain preexisting lung
diseases (e.g., asthma)
Higher susceptibility to respiratory infection
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12.13.1.1 Stratospheric vs. Atmospheric and Ambient Ozone
The phrase good up high, bad nearby has been used by the EPA to make the distinction between
ozone in the upper and lower atmosphere. Ozone in the upper atmosphere (referred to as strato
-
spheric ozone) helps filter out damaging ultraviolet radiation from the sun. Though ozone in the
stratosphere is protective, ozone in the atmosphere, which is the air we breathe, can be harmful to
the respiratory system. Harmful levels of ozone can be produced by the interaction of sunlight with
certain chemicals emitted to the environment (e.g., automobile emissions and chemical emissions
of industrial plants). These harmful concentrations of ozone in the atmosphere are often accompa
-
nied by high concentrations of other pollutants, including nitrogen dioxide, fine particles, and
hydrocarbons. Whether pure or mixed with these or other chemicals, ozone can be harmful to health.
12.13.1.2 Concentrations
At concentrations that do not exceed public health standards, ozone has little potential to remove
indoor air contaminants. For many of the chemicals commonly found in indoor environments, the
reaction process with ozone may take months or years (Boeniger, 1995).
For all practical purposes,
ozone does not react at all with such chemicals. Ozone generators are not effective in removing
carbon monoxide (Salls, 1927; Shaughnessy et al., 1994) or formaldehyde (Esswein and Boeniger,

1994). In an experiment designed to produce formaldehyde concentrations representative of an
embalming studio, where formaldehyde is the main odor producer, ozone showed no effect in
reducing formaldehyde concentration (Esswein and Boeniger, 1994). Other experiments suggest
that body odor may be masked by the smell of ozone but is not removed by ozone (Witheridge
and Yaglou, 1939). Ozone is not considered useful for odor removal in building ventilation systems
(ASHRAE, 1989).
Some odorous chemicals will react with ozone. For example, in some experiments, ozone
appeared to react readily with certain chemicals, including some chemicals that contribute to the
smell of new carpet (Weschler et al., 1992b; Zhang and Lioy, 1994). Ozone is also believed to
react with acrolein, one of the many odorous and irritating chemicals found in secondhand tobacco
smoke.
For many of the chemicals with which ozone does readily react, the reaction can form a variety
of harmful or irritating by-products (Weschler et al., 1992a,b, 1996; Zhang and Lioy, 1994). For
example, in a laboratory experiment that mixed ozone with chemicals from new carpet, ozone
reduced many of these chemicals, including those that can produce new carpet odor. However, in
the process, the reaction produced a variety of aldehydes, and the total concentration of organic
chemicals in the air increased rather than decreased after the introduction of ozone (Weschler et
al., 1992b). In addition to aldehydes, ozone may also increase indoor concentrations of formic acid
(Zhang and Lioy, 1994), both of which can irritate the lungs if produced in sufficient amounts.
Some of the potential by-products produced by the reactions of ozone with other chemicals are
themselves very reactive and capable of producing irritating and corrosive by-products (Weschler
and Shields, 1997a,b; Weschler et al., 1996). Given the complexity of the chemical reactions that
occur, additional research is needed to more completely understand the complex interactions of
indoor chemicals in the presence of ozone.
Some studies show that ozone concentrations produced by ozone generators can exceed health
standards even when one follows manufacturer’s instructions. Many factors affect ozone concen
-
trations, including the amount of ozone produced by the machines, the size of the indoor space,
the amount of material in the room with which ozone reacts, the outdoor ozone concentration, and
the amount of ventilation. These factors make it difficult to control the ozone concentration in all

circumstances.
Results of some controlled studies show that concentrations of ozone considerably higher than
these standards are possible even when a user follows the manufacturer’s operating instructions.
© 2003 BY CRC PRESS LLC
The many brands and models of ozone generators on the market vary in the amount of ozone
produced. In many circumstances, the use of an ozone generator may not result in ozone concen
-
trations that exceed public health standards. But, many factors affect the indoor concentration of
ozone so that under some conditions, ozone concentrations may exceed public health standards.
In one study (Shaughnessy and Oatman, 1991), a large ozone generator recommended by the
manufacturer for spaces up to 3000 square feet was placed in a 350-ft
2
room and run at a high
setting. The ozone in the room quickly reached concentrations that were exceptionally high — 0.50
to 0.80 ppm, which is 5 to 10 times higher than public health limits.
In an EPA study, several different devices were placed in a home environment in various rooms,
with doors alternately opened and closed and with the central ventilation system fan alternately
turned on and off. The results showed that some ozone generators, when run at a high setting with
interior doors closed, would frequently produce concentrations of 0.20 to 0.30 ppm. A powerful
unit set on high with the interior doors opened achieved values of 0.12 to 0.20 ppm in adjacent
rooms. When units were not run on high and interior doors were open, concentrations generally
did not exceed public health standards.
The concentrations reported above were adjusted to exclude that portion of the ozone concen-
tration brought in from the outdoors. Indoor concentrations of ozone brought in from outside are
typically 0.01 to 0.02 ppm, but could be as high as 0.03 to 0.05 ppm (Hayes, 1991; USEPA, 1996b;
Weschler et al., 1989, 1996; Zhang and Lioy, 1994). If the outdoor portion of ozone were included
in the indoor concentrations reported above, the concentrations inside would have been correspond
-
ingly higher, increasing the risk of excessive ozone exposure. None of the studies reported here
involved the simultaneous use of more than one device. The simultaneous use of multiple devices

increases the total ozone output and therefore greatly increases the risk of excessive ozone exposure.
The actual concentration of ozone produced by an ozone generator depends on many factors:
• Concentrations will be higher if a more powerful device or more than one device is used, if a
device is placed in a small space rather than a large space, if interior doors are closed rather than
open, if the room has fewer rather than more materials and furnishings that adsorb or react with
ozone, and (provided that outdoor concentrations of ozone are low) if there is less rather than more
outdoor air ventilation.
• The proximity of a person to the ozone-generating device can also affect one’s exposure. The
concentration is highest at the point where the ozone exits from the device and generally decreases
as one moves further away.
Manufacturers and vendors advise users to size the device properly to the space or spaces in
which it is used. Unfortunately, some manufacturers’ recommendations about appropriate sizes for
particular spaces have not been sufficiently precise to guarantee that ozone concentrations will not
exceed public health limits.
Ozone generators typically provide a control setting by which the ozone output can be adjusted.
The ozone output of these devices is usually not proportional to the control setting. The relationship
between the control setting and the output varies considerably among devices. In experiments to
date, the high setting in some devices generated 10 times the level obtained at the medium setting
(USEPA, 1995). Manufacturers’ instructions on some devices link the control setting to room size
and thus indicate what setting is appropriate for different room sizes. However, room size is only
one factor affecting ozone levels in the room. In addition to adjusting the control setting to the size
of the room, users have sometimes been advised to lower the ozone setting if they can smell the
ozone. Unfortunately, the ability to detect ozone by smell varies considerably from person to person,
and one’s ability to smell ozone rapidly deteriorates in the presence of ozone. While the smell of
ozone may indicate that the concentration is too high, lack of odor does not guarantee that levels
are safe.
At least one manufacturer is offering units with an ozone sensor that turns the ozone generator
on and off with the intent of maintaining ozone concentrations in the space below health standards.
© 2003 BY CRC PRESS LLC
The EPA is currently evaluating the effectiveness and reliability of these sensors and plans to

conduct further research to improve society’s understanding of indoor ozone chemistry. The EPA
will report its findings as the results of this research become available.
12.13.1.3 Particulates
Ozone does not remove particles (e.g., dust and pollen) from the air, including the particles
that cause most allergies; however, some ozone generators are manufactured with an ion generator
or ionizer in the same unit. An ionizer is a device that disperses negatively (and/or positively)
charged ions into the air. These ions attach to particles in the air, giving them a negative (or positive)
charge so that the particles may attach to nearby surfaces such as walls or furniture, or attach to
one another and settle out of the air. The effectiveness of particle air cleaners, including electrostatic
precipitators, ion generators, or pleated filters, varies widely.
12.13.1.4 Biological Effect
If used at concentrations that do not exceed public health standards, ozone applied to indoor
air does not effectively remove viruses, bacteria, mold, or other biological pollutants. Some
data suggest that low levels of ozone may reduce airborne concentrations and inhibit the growth
of some biological organisms while ozone is present, but ozone concentrations would have to
be 5 to 10 times higher than public health standards allow before the ozone could decontaminate
the air sufficiently to prevent survival and regeneration of the organisms once the ozone is
removed (Dyas et al., 1983; Foarde et al., 1997). Even at high concentrations, ozone may have
no effect on biological contaminants embedded in porous material such as duct lining or ceiling
tiles (Foarde et al., 1997). In other words, ozone produced by ozone generators may inhibit
the growth of some biological agents while it is present, but it is unlikely to fully decontaminate
the air unless concentrations are high enough to be a health concern if people are present.
Even with high levels of ozone, contaminants embedded in porous material may not be affected
at all.
12.13.1.5 Water
Ozone has been extensively used for water purification, but ozone chemistry in water is not the
same as ozone chemistry in air. High concentrations of ozone in air, when people are not present,
are sometimes used to help decontaminate an unoccupied space from certain chemical or biological
contaminants or odors (e.g., fire restoration). However, little is known about the chemical by-
products left behind by these processes (Dunston and Spivak, 1997). While high concentrations of

ozone in air may sometimes be appropriate in these circumstances, conditions should be sufficiently
controlled to ensure that no person or pet becomes exposed. Ozone can adversely affect indoor
plants and damage materials such as rubber, electrical wire coatings and fabrics and artwork
containing susceptible dyes and pigments
.
12.14 PHENOLS
Phenolic compounds (e.g., carbolic acid, Lysol
®
, hexylresorcinol, hexachlorophene) dena-
ture proteins and disrupt cell membranes. They are used as antiseptics at low concentrations
and as disinfectants at high concentrations. Carbolic acid was first used by Lister in the 1860s
and became the standard against which all other disinfectants were compared. Phenol is a
colorless-to-white solid when pure; however, the commercial product, which contains some
© 2003 BY CRC PRESS LLC
water, is a liquid. It has a distinct odor that is sickeningly sweet and tarry. Most people begin
to smell phenol in the air at about 40 ppb, and in water at about 1 to 8 ppm. Note that these
levels are lower than the levels at which adverse health effects have been observed in animals
that have breathed air containing phenol or have drunk water containing phenol. Phenol
evaporates more slowly than water, and a moderate amount can form a solution with water.
Phenol can catch on fire. It occurs naturally or can be manmade.
Phenol is used as a slimicide (a chemical toxic to bacteria and fungi characteristic of aqueous
slimes), as a disinfectant, and in medicinal preparations such as over-the-counter treatments for
sore throats. Phenol is ineffective against spores and is a poor viricide; however, it is a good
fungicide in terms of destroying vegetative structures. It works in combination with soap and is
good in a saline solution or at warm temperature.
After World War II, a variety of phenol derivatives, phenolics, were developed, including ortho-
phenyl phenol, which is a cresol and is found in Lysol. Other cresols are used in creosote as
environmental disinfectants and fungicides. Hexylresorcinol reduces surface tension and is used as
an antiseptic, in mouthwashes, and in throat lozenges. Hexachlorophene (G-11) was widely used
as a topical scrub and skin antisepsis. In 1972, hexachlorophene was shown to be easily absorbed

through the skin. After absorption, hexachlorophene enters the blood stream and ultimately causes
neurological damage. Newborns and the elderly, with less subcutaneous fat, are at greater risk for
brain damage. These compounds work by denaturing cell proteins, inactivating enzymes, and
damaging cell membranes.
12.15 SOAPS AND SYNTHETIC DETERGENTS
Soaps and synthetic detergents act by mechanical removal of contaminants by decreasing surface
tension on the contaminated substrate. These compounds are mildly germicidal wetting agents. A
detergent is any surface-tension depressant (keeps organisms spread out).
12.15.1 Anionic Detergents
For anionic detergents, the negatively charged portion of the molecule is the active part. These
detergents are not considered broadbased germicides but may work against Gram-positive bacteria.
C
12
H
25
OSO
3
attached to Na
+
is a common formulation. Examples are sodium laurel sulfate and Dreft.
12.15.2 Cationic Detergents
For cationic detergents, the positively charged portion of the molecule is the active part. Cationic
detergents are very germicidal; CPC (cetyl pyridinium chloride) is used in mouthwash and tooth
-
paste (e.g., the mouthwash Cepacol

). Cationic detergents cause inactivation of enzymes and
destruction of cell membranes. Quaternary ammonium compounds can be in concentrations as low
as 1:30,000 and still be cidal. Zephiran, Phemerol, Diaparene, and Ceepryn
are all examples of

cationic detergents.
12.15.3 Nonionic Detergents
Nonionic detergents are not germicidal, are good surfactants, and are primarily used as laundry
detergents.
© 2003 BY CRC PRESS LLC
12.16 IRRADIATION OR ULTRAVIOLET LIGHT
Irradiation usually destroys or distorts nucleic acids. Ultraviolet light is commonly used to
sterilize the surfaces of objects. X-rays and microwaves are possibly useful, especially for
endospores. Many spoilage organisms are easily killed by irradiation.
12.17 DESICCANTS
For drying (removal of H
2
O), the reduced water activity (αw < 0.90) produced by dessication
will destroy cellular microorganisms in their vegetative state. Desiccation is not reliable for
endospores or viruses. Desiccation occurs through application of heat, evaporation, freeze-drying,
addition of salt or sugar, or application of desiccant chemicals.
12.18 LOW TEMPERATURES
Most organisms grow very little or not at all at 0°C. Low temperatures, however, are not
bactericidal.
12.19 EQUIPMENT DECONTAMINATION OR DISPOSAL
Personal protective equipment and other equipment used on site must be either decontaminated
or properly disposed. Because biocides can destroy some equipment, more disposal may be needed
than that estimated for asbestos or lead abatement projects. Respirators can be decontaminated
using chlorine solution and sequential rinses. Respirator filters and cartridges cannot be decontam
-
inated and should not be used for more than one work day. Storage of biologically contaminated
respirator filters and cartridges may cause residual biological contaminants to amplify through
reproduction. Thus, if respirator filters and cartridges are worn on successive day, workers will be
exposed over and over again to the growing biological contamination in their filters and cartridges.
Amplification is particularly troublesome in HEPA filters, whether used on respirators or to

filter interior air streams. When used in respirators, these filters, if contaminated, may continually
expose workers within the very small breathing portal space provided by the interior of respirators.
If filtration units are contaminated, air containing unacceptable levels of biological contaminants
may be vented from the decontamination area.
All filtration units used for area air filtration must be checked to ensure that filtration continues
to be adequate for occupied spaces. When at all possible, venting should be outdoors where human
receptors are not present. Filtration may be checked using the same air monitoring techniques used
to gauge biological contamination in workplace air. If air is vented when biocides are in use, the
level of biocides present in vented air may also need to be checked. Vessels used to store biocides
may not be usable again. The manufacturers’ recommendations should be consulted and docu
-
mented as to reuse of pails, buckets, mops, handheld tools, polyethylene sheeting, and other
equipment exposed to biocides. Porous materials, such as fibrous booms and spill mats, cannot be
decontaminated and should be disposed. Vacuums, whether dry or wet, and negative air machines
should be decontaminated in accordance with manufacturers’ recommendations.
© 2003 BY CRC PRESS LLC
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