Abstract
Severity of the risk associated with indoors sewage contamination is oftentimes underestimated by
uninformed homeowners. Threats to health and effects on weakened immune system associated with
sewage backflow and resulting from air-born and other pathogens should be known and addressed
when performing mitigation. Type of contaminated material, degree of contamination and length of
time of sewage impact should be considered when choosing disinfectants to ensure safe mitigation.
Introduction
When thinking about water, a common misconception limits definition to a clear, odorless, and
tasteless liquid, essential for most plant and animal life (Farlex Dictionary, 2011). What is often
forgotten, is that waste waters and any fluids normally secreted from the body are also a part of the
definition; thereby, making water the most enduring and continuing damaging matter in the indoor
environment.
Water is also the most widely used substance for solvents. Its dissolving quality and associated
dangers are well known to professional water and sewage damage mitigators, restorers,
environmental engineers and public health professionals, whose purpose is to guard individuals’
health from harmful effects of sewage contamination. Their primary goal, simply put, is to immediately
prevent individual’s contact with sewage, stop further flow of contaminated water, eliminate dangerous
matter present in this water, bring indoor environment back to dry state, and reclaim fluids.
Potential of negative effect sewage has on human health depends on various factors ranging from the
length of time sewage was left untreated, and the source and content of sewage. The degree and
significance of threat to human health also depends on the extent of penetration and type of materials
affected and is directly associated with materials’ porosity and amount of sewage.
For example, a small quantity of sewage resulting from a limited and disrupted backflow contained to a
specific location and deposited on a tile floor can be easily cleaned up using extraction, cleaning, and
disinfection. Still, mitigation should be performed as soon as possible to reduce sewage impact time
and prevent contact with absorbent materials. Fast decontamination in this instance will reduce
potential health risks effectively.
Another example may include waste that flows beyond the limits of the sewage system, enters the
structure and penetrates adjacent areas with porous materials, such as carpet or linoleum. Here,
sewage damage is still confined to a specific area and its quantity is limited, but access to adjacent
area may have occurred through the wall and waste waters have therefore penetrated complex
surfaces such as walls, baseboards as well as highly porous materials such as carpet and carpet
padding. As in the example above, decontamination off all affected materials is required. Additionally,
restoration should consist of not only disinfection, but also evaluation of the
contaminated materials for replacement. If aggressive disinfection treatment or porous wall materials
is unlikely to succeed, such materials should be removed. Effective restorer must also lift and treat
both sides of the carpet, dispose of the carpet padding, and ensure drying of all surfaces post-
disinfection.
The last example covers the most complex of the reviewed situations, when sewage originated in the
building backflows into the building, after coming in touch with sewage from the main line of the
sewage system, and contaminates the structure, penetrating its materials and furnishings. Pathogenic
raw waste contained in building and furnishings in this situation poses severe risk to human health
and requires immediate evacuation of all occupants. When sewage backflow originates or comes in
touch with an outside sewage system, restoration should begin instantaneously and follow strict safety
rules to protect health of restoration and cleaning crew.
Protection of the cleaning and restoration professionals is achieved by proper use of high-efficiency
particulate air filters, goggles, gloves, rubber boots, and sewage-proof suites. Additionally, any
puncture wounds, scratches and other wounds with broken skin should be avoided and those with
open sores and like injuries should not be
allowed at restoration site to prevent possibility of dangerous infection.
Sewage Problem: Review
Problems with sewage back up and building contamination caused by organic matter, backflow from
septic lines, or outside contaminated water sources, like rain water or river overflow, pose a severe
threat to human health. In some instances, an immediate damage to materials occurs, while in others,
it is only a question of time how soon
materials and structure will be damaged expensively.
In situations when determination of the cause of the sewage backflow must be made, further damage
prevented, and the problem fixed, time is of a great importance. If all of the above is not addressed in
a short period of time, preferably immediately, a number of days may pass before sewage damage
mitigation begins. Therefore, allowing for a deep penetration of sewage or other contaminants into
porous and highly absorbent materials.
Absorbent or Hygroscopic Materials
Some materials are more likely than others to attract water molecules and increase in volume, weight,
or otherwise change its physical characteristics. Prolonged presence of moisture in hygroscopic
materials also results in microbial growth; that is when many homeowners recognize odor. The most
absorbent or hygroscopic (‘water seeking’) materials include paper, carpet, carpet padding, gypsum,
and wood. When these and other materials are penetrated with sewage, water, or organic matter,
opportunistic microorganisms or bacteria with the potential of causing disease may develop.
Such potentially disease-causing microorganisms present a severe hazard to human health, because
toxic and damaging matter may be produced as a result of their growth and development. For
example, toxigenic fungi, commonly known as mold, can grow extensively on structural materials or
furnishings inside a building as a result of high humidity, causing damage to those with weakened
immune system and releasing harmful toxins that pose serious risk to any occupant.
Sewage Damage: Analysis & Plan of Action
Following sewage damage or flooding, mitigation professionals or other parties involved should
determine health hazards associated with the problem and the effect of this damage on the structure
and contents. The Heating, Ventilating, and Air Conditioning systems should be reviewed for safety
and necessity of treatment. Safe and Institute For Inspection Cleaning And Restoration – approved
environment testing methods should be used.
After determination is made regarding necessity of evacuation of the occupants from a portion of the
building or the entire structure, a plan should be drawn on how to clean and repair the damage and
what is necessary for this process.
In order to determine scope of work, semi porous materials should be evaluated and decision should
be made to restore or replace each affected/contaminated item/surface. During this process, the type
of damaged materials, the nature, the source, water volume, and severity of the contamination should
be determined.
The sewage or flood-damaged materials may be organic or synthetic, porous, nonporous, or semi
porous. The nature of damage may be a natural disaster like flooding or river overflow; septic tank
overflow; main sewer line back up, and so on (cause of any of these problems is a different matter).
Another important aspect of remediation is the micro flora: pathogens contained in sewage, organic
matter, debris carried from outdoors, pathogens and allergens. The micro flora poses one of the main
concerns, because it serves as a source of viral, parasitic, bacterial, and fungal activity. Sewage-
borne microorganisms and bacteria have potential to transmit to occupants and remediation crew.
Potential of risk to human health may be aggravated by the temperature and humidity of the
surrounding environment (indoors and out), because it can create a comfortable development and
survival environment for these microorganisms and bacteria.
Severity of the risk associated with indoors sewage contamination is oftentimes underestimated by
uninformed homeowners. Threats to health and effects on weakened immune system associated with
sewage backflow and resulting from air-born and other pathogens should be known and addressed
when performing mitigation. Type of contaminated material, degree of contamination and length of
time of sewage impact should be considered when choosing disinfectants to ensure safe mitigation.
Introduction
When thinking about water, a common misconception limits definition to a clear, odorless, and
tasteless liquid, essential for most plant and animal life (Farlex Dictionary, 2011). What is often
forgotten, is that waste waters and any fluids normally secreted from the body are also a part of the
definition; thereby, making water the most enduring and continuing damaging matter in the indoor
environment.
Water is also the most widely used substance for solvents. Its dissolving quality and associated
dangers are well known to professional water and sewage damage mitigators, restorers,
environmental engineers and public health professionals, whose purpose is to guard individuals’
health from harmful effects of sewage contamination. Their primary goal, simply put, is to immediately
prevent individual’s contact with sewage, stop further flow of contaminated water, eliminate dangerous
matter present in this water, bring indoor environment back to dry state, and reclaim fluids.
Potential of negative effect sewage has on human health depends on various factors ranging from the
length of time sewage was left untreated, and the source and content of sewage. The degree and
significance of threat to human health also depends on the extent of penetration and type of materials
affected and is directly associated with materials’ porosity and amount of sewage.
For example, a small quantity of sewage resulting from a limited and disrupted backflow contained to a
specific location and deposited on a tile floor can be easily cleaned up using extraction, cleaning, and
disinfection. Still, mitigation should be performed as soon as possible to reduce sewage impact time
and prevent contact with absorbent materials. Fast decontamination in this instance will reduce
potential health risks effectively.
Another example may include waste that flows beyond the limits of the sewage system, enters the
structure and penetrates adjacent areas with porous materials, such as carpet or linoleum. Here,
sewage damage is still confined to a specific area and its quantity is limited, but access to adjacent
area may have occurred through the wall and waste waters have therefore penetrated complex
surfaces such as walls, baseboards as well as highly porous materials such as carpet and carpet
padding. As in the example above, decontamination off all affected materials is required. Additionally,
restoration should consist of not only disinfection, but also evaluation of the
contaminated materials for replacement. If aggressive disinfection treatment or porous wall materials
is unlikely to succeed, such materials should be removed. Effective restorer must also lift and treat
both sides of the carpet, dispose of the carpet padding, and ensure drying of all surfaces post-
disinfection.
The last example covers the most complex of the reviewed situations, when sewage originated in the
building backflows into the building, after coming in touch with sewage from the main line of the
sewage system, and contaminates the structure, penetrating its materials and furnishings. Pathogenic
raw waste contained in building and furnishings in this situation poses severe risk to human health
and requires immediate evacuation of all occupants. When sewage backflow originates or comes in
touch with an outside sewage system, restoration should begin instantaneously and follow strict safety
rules to protect health of restoration and cleaning crew.
Protection of the cleaning and restoration professionals is achieved by proper use of high-efficiency
particulate air filters, goggles, gloves, rubber boots, and sewage-proof suites. Additionally, any
puncture wounds, scratches and other wounds with broken skin should be avoided and those with
open sores and like injuries should not be
allowed at restoration site to prevent possibility of dangerous infection.
Sewage Problem: Review
Problems with sewage back up and building contamination caused by organic matter, backflow from
septic lines, or outside contaminated water sources, like rain water or river overflow, pose a severe
threat to human health. In some instances, an immediate damage to materials occurs, while in others,
it is only a question of time how soon
materials and structure will be damaged expensively.
In situations when determination of the cause of the sewage backflow must be made, further damage
prevented, and the problem fixed, time is of a great importance. If all of the above is not addressed in
a short period of time, preferably immediately, a number of days may pass before sewage damage
mitigation begins. Therefore, allowing for a deep penetration of sewage or other contaminants into
porous and highly absorbent materials.
Absorbent or Hygroscopic Materials
Some materials are more likely than others to attract water molecules and increase in volume, weight,
or otherwise change its physical characteristics. Prolonged presence of moisture in hygroscopic
materials also results in microbial growth; that is when many homeowners recognize odor. The most
absorbent or hygroscopic (‘water seeking’) materials include paper, carpet, carpet padding, gypsum,
and wood. When these and other materials are penetrated with sewage, water, or organic matter,
opportunistic microorganisms or bacteria with the potential of causing disease may develop.
Such potentially disease-causing microorganisms present a severe hazard to human health, because
toxic and damaging matter may be produced as a result of their growth and development. For
example, toxigenic fungi, commonly known as mold, can grow extensively on structural materials or
furnishings inside a building as a result of high humidity, causing damage to those with weakened
immune system and releasing harmful toxins that pose serious risk to any occupant.
Sewage Damage: Analysis & Plan of Action
Following sewage damage or flooding, mitigation professionals or other parties involved should
determine health hazards associated with the problem and the effect of this damage on the structure
and contents. The Heating, Ventilating, and Air Conditioning systems should be reviewed for safety
and necessity of treatment. Safe and Institute For Inspection Cleaning And Restoration – approved
environment testing methods should be used.
After determination is made regarding necessity of evacuation of the occupants from a portion of the
building or the entire structure, a plan should be drawn on how to clean and repair the damage and
what is necessary for this process.
In order to determine scope of work, semi porous materials should be evaluated and decision should
be made to restore or replace each affected/contaminated item/surface. During this process, the type
of damaged materials, the nature, the source, water volume, and severity of the contamination should
be determined.
The sewage or flood-damaged materials may be organic or synthetic, porous, nonporous, or semi
porous. The nature of damage may be a natural disaster like flooding or river overflow; septic tank
overflow; main sewer line back up, and so on (cause of any of these problems is a different matter).
Another important aspect of remediation is the micro flora: pathogens contained in sewage, organic
matter, debris carried from outdoors, pathogens and allergens. The micro flora poses one of the main
concerns, because it serves as a source of viral, parasitic, bacterial, and fungal activity. Sewage-
borne microorganisms and bacteria have potential to transmit to occupants and remediation crew.
Potential of risk to human health may be aggravated by the temperature and humidity of the
surrounding environment (indoors and out), because it can create a comfortable development and
survival environment for these microorganisms and bacteria.
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Water is the single most long term destructive substance in the indoor environment. It dissolves or
controlling water damage are well known to professional restorers and public health professionals.
These objectives are to protect public health, immediately remove harmful substances that enter in
the environment with flowing water, restore the environment to a dry state, and salvage valuable fluids
or wastes (e.g., raw sewage) or other organic contaminants.
Sewage poses a very significant threat to human health. However, the severity of the health threat
depends on the content of the sewage and the degree and extent of penetration into the building
environment. The degree of penetration is dependent on the porosity of contaminated materials, the
quantity of sewage, and the amount of time the sewage remains in contact with materials. Consider
different in each situation.
Situation 1. A very limited quantity of waste that originates in the built environment is deposited or
flows slightly beyond the confines of the sewage system. In this situation, the waste is found in one
specific location, is contained, and does not penetrate the building structure. A limited amount of
contact time has occurred. An example of this situation might be waste that overflows in a bathroom
and is deposited on and confined to a tile floor. In this situation, there is a limited quantity of waste,
which is contained and does not contact absorbent materials. Decontamination, which includes water
extraction, cleaning, and disinfection, can be effective in reducing this particular potential health risk.
Situation 2. Waste that originates in the built environment is deposited or flows beyond the confines
of the building’s disposal system. In this case, there is limited or confined flooding, but water and
waste penetrate the structure and furnishings of the building. For example, flooding occurs in a men’s
room of an office building, water flows under a wall and into the carpet of an adjacent hallway. In this
case, there is a limited amount of waste that is confined to a relatively small area of the building, but it
penetrates regions of the environment that have complex surfaces and are difficult to restore.
Effective restoration involves decontamination (as in Situation 1) as above and drying all surfaces that
have been in contact with the sewage. In the case of stretch-in carpet, lifting and cleaning the
contaminated carpet, disposing of the cushion, and treating both sides of the carpet thoroughly with a
disinfectant are all necessary. Affected porous wall materials need to be treated with a disinfectant
and evaluated for replacement. Because of the confinement of the sewage spill, aggressive,
comprehensive treatment can be effective.
Situation 3. Waste that originates in the built environment, along with other wastes from the main line
of the sewage system, is backed up into the immediate environment, where the waste is widely
dispersed and penetrates both the structure and its furnishings. In this situation, there is extensive
risk because humans can be exposed to pathogenic raw wastes that have penetrated and become
contained by the building and its furnishings. If flooding is from this kind of primary outside sewage
system, occupants should be evacuated, and restoration should begin immediately. In this situation,
cleaning and restoration professionals should be protected by using respirators with high-efficiency
particulate air (HEPA) cartridges, rubber boots, gloves, splash goggles, and protective garments.
Extreme care should be taken to avoid puncture wounds during the restoration process. Restoration
staff who have cuts or open sores should not be allowed to work on this kind of restoration project.
The principles of restoration of this situation are outlined in the last section of this paper, which
contains specific recommendations for techniques. The main discussion of this paper focuses on the
potential health risks posed by a sewage backup similar to Situation 3.
Description of the Primary Problem
When a building is contaminated with sewage backing up from the septic lines, or flooding of a
building occurs that involves sewage or a heavy load or organic matter, as in the case of river
flooding, a serious threat to human health exists. Without appropriate action, extensive damage to
materials will occur immediately or in time. Several days may elapse before the cause of the backup
is determined, the problem is corrected, and flooding subsides. This allows extensive permeation and
contamination of absorbent (hygroscopic) materials such as wood, gypsum, paper, and concrete to
occur. This penetration with water and organic matter leads to the growth of potentially disease-
causing (or opportunistic) microorganisms. These Organisms may pose a serious health risk to
occupants of the building. Organic matter and water-saturated materials can be used as substrate for
growth of microorganisms (such as gram-negative bacteria and toxigenic fungi) that can produce
substances toxic to humans and damaging to materials. A large amount of water inside a building will
cause high humidity, which can also contribute to microbial growth on structural materials and
contents (2).
Questions To Be Raised After Sewage Contamination
Some of the questions to be answered in this situation include the following: What are the effects of
the initial contamination of the building, its contents, and the health and welfare of its occupants?
What is needed to thoroughly clean up the contamination and repair the damage? Should the entire
building or a portion of the building be evacuated and, if so, for how long? Can semi porous materials
be decontaminated, or should they be replaced? What are the consequences of using inadequate
measures to remediate the damage? What are the indicators that help determine when the building is
safe or not safe for occupancy? What methods should be used to test for these indicators? What is
the effect of the sewage damage on other systems, especially the air changing systems (ACS) and
the heating, ventilating, and air conditioning (HVAC) systems in the build environment?
Issues of Concern Associated with the Problem
There are several factors bearing on the remediation of the problem. Among these are the nature of
the contamination, the types of water-damaged materials (organic or synthetic; porous, semi porous,
or nonporous), the sewagemicroflora (pathogens and allergens), organic matter load, water volume,
and impact of ambient outdoor temperature and humidity on the indoor environment. Of major
concern are the survival of sewage-borne micro flora (viral, bacterial, fungal, parasitic, and their
potential transmission to humans. The potential exists for some fungal and bacterial contaminants to
establish an ecological niche and present a health risk from chronic exposure for some time after the
event.
Scope of These Guidelines
The discussions within this paper will address the immediate and longer term effects of sewage-
flooding contamination on the building’s structural materials and contents; the potential effects on
occupants; and the steps to remove contamination to include flushing with clean water and detergent
solutions, vacuuming, dehumidification, and disinfection. The potential health threats presented at
each stage of remediation will be discussed. These include the production of bioaerosols during
removal of gross contamination, the long-term effects of residual moisture and organic matter on the
building and occupants, and the colonization and growth of non-sewage-borne species of
microorganisms such as molds and other fungi.
Assessment of Damage and Danger to Health
The factors that determine the extent of contamination within the building include the volume and the
solids content of the sewage backflow, whether flooding is isolated to the basement or involves other
levels as well, and how long the contamination has been in place.
The assumption must be that potential pathogens are present in the contamination. Such microbial
contamination includes bacteria, fungi, viruses, and parasites. Table 1 lists the micro flora that may
be found in raw, untreated sewage and the diseases that these organisms have the potential to cause
(3). Also, hypersensitivity lung disease has been shown to be caused by repeated flooding of homes
with sewer water (4).
The routes of exposure of the building occupants to these pathogens are contact, ingestion, and
inhalation. An incomplete or inadequate job of cleaning and disinfection may leave residue that can
be a substrate for disease-causing microorganisms. Occupants may be infected by contacting
contaminated surfaces, with inadvertent transmission from hands to mouth, or aerosolization of
contamination may result in the inhalation of microorganisms or their products (e.g., endotoxins).
Residue and microbial contaminants also can be tracked by occupants’ feet to other parts of the
building.
Another aspect of health impact is that the conditions caused by sewage backflow or flooding are
conductive to the growth of nonsewage microorganisms. These conditions include wetness, humidity,
and organic matter. Microorganisms, which exist in various life stages in both indoor and outdoor
environments, would then have the opportunity for exponential population growth. These species
(see Table 2) can produce bioaerosols, which are potential sources for disease. For example, mold
allergy is a common source of indoor air symptoms and complaints (5).
In regard to the susceptibility of building occupants, those individuals whose immune systems are in
some way compromised (i.e., immunocompromised), or who are otherwise susceptible due to age,
medication, or underlying illness, are considered to be at greater risk of contracting potentially fatal
infections than those individuals who are healthy.
Fundamental Considerations for Remediation
The factors to be considered in remediation include the types of materials affected, assessment of the
degree of damage, the extent of contaminated absorbent material, the total contact time, the humidity,
and the amount of ventilation available. The primary goal of remediation must be the complete
removal and disposal of water and contamination using the sanitary sewer system if possible. Wet
extraction systems should be used to completely remove sewage and water used for cleaning. As
part of this phase of the operation, removal of affected contents and structural materials may be
necessary. These items could include carpet, wall covering porous wallboard, and insulation, and
other substrates with the potential for mold growth. Disposal of nonrestorable contaminated materials
requires that the materials be confined in plastic bags and transported to appropriate disposal
facilities. In all cases, workers must be provided with appropriate personal protective equipment such
as respirators, boots, gloves, splash goggles, and coveralls, and with equipment with which to remove
contamination (6).
In order to speed the drying process, both mechanical and natural dehumidification should be
employed as the gross contamination is removed and during restoration. An indoor humidity target of
40% relative humidity (RH) or less should be attained as quickly as possible (7). If possible,
depending on the design of the contaminated space and the outdoor weather conditions, there
should be ventilation with fans and evaporation of indoor water by introducing outside air. The use of
dehumidifiers for removal of moisture from inside building surfaces and air is recommended. The
ACS and HVAC systems may be considered as dehumidifiers, depending on the systems’ mechanical
capacity versus the extent of moisture load over time. Rapid drying that stresses proper management
of temperature, airflow, and dehumidification is essential for success.
Desiccant dehumidifiers, using silica-gel or lithium chloride, could be employed as an adjunct to
disinfection to reduce RH to as low a level as possible (8). Moisture content measurements of
reclaimed materials is an important criterion of the success of adequate drying and the remediation
process.
Chemical Disinfection
The process of decontamination and disinfection will be important to ensure the elimination of
pathogens and organisms that were contained in the sewage or that grew during the period of
contamination. Even concrete can be colonized and broken down my microorganisms if it is allowed
to remain wet and contaminated by organic matter. Chemicals categorized as disinfectants are
appropriate in this application. A disinfectant may be defined as an agent that reduces significant
numbers of pathogens on inanimate objects to a level below the expected to cause disease.
Disinfectants may not kill spores, however, and, because some bacterial and fungal spores will always
be present in the environment, it would not be feasible to attempt to kill all of the spores in an affected
area. Emphasis instead should be placed on removal of the substrates, water, and organic matter
needed for the growth of spores.
Choice of disinfectants depends on the degree of microbial killing required, the nature of surfaces to
be treated, application safety, and the cost and ease of use of available agents. It is recommended
that disinfectants be used in accordance with the manufacturer’s instructions for use and dilution.
Classes of disinfectants and their common-use dilutions include alcohols (60 to 90% in water),
quaternary ammonium compounds (0.4 to 1.6%), phenolics (0.5 to 5%), iodophores (75 ppm),
glutaraldehydes (2%), household bleach (sodium hypochlorite, diluted 10%), and hydrogen peroxide
(3 to 6%). The advantages and disadvantages of each of these disinfectants are given in Table 3.
For example, the use of iodophores or low-concentration chlorine compounds would require that little
organic matter be present on surfaces, a condition that may be difficult to achieve. Caution should be
used in mixing some disinfectants. For example, mixing chlorine-containing solutions with ammonia or
amine solutions will produce extremely toxic vapors, and could have lethal effects on workers or
building occupants. Of critical importance is “contact time”. Contact time is the length of time that the
disinfectant is permitted to work on the contaminated surface. The contact time must be at least 15
min before additional cleaning and removal of the disinfectant is undertaken. Some disinfectants,
such as phenolics and glutaraldehydes, leave a residue that continues to suppress microbial growth
for some time after treatment.
Health-Based Recommendation for Mitigation
The following specific guidelines are presented with a goal of restoring the contaminated area such
that the health of occupants is protected from any risk of pathogen-caused disease.
Remediation should begin as soon as possible. The longer the contamination is allowed to persist,
the greater the potential for microbial growth and resultant damage.
Unprotected occupants and workers should be evacuated from the affected areas during the initial
stages of decontamination, cleaning, and disinfection (e.g., until sewage has been removed and
disinfectants applied).
Technicians in the vicinity of the sewage during the initial stages of decontamination, cleaning, and
disinfection should be equipped with an organic vapor HEPA respirator, rubber gloves, splash
goggles, and boots. In the case of overhead contamination, technicians should also be equipped with
goggles, hard hats, and protective suits. Technicians should report any wounds that occur during
restoration and take care to avoid “cross-contamination” from affected to unaffected areas by foot
traffic or material handling.
After water removal, all affected materials should be decontaminated by spraying with a disinfectant
solution. It is not the intent of this prespray to effect full disinfection because the presence of
organics precludes this. The objective is to initiate the reduction and containment of microorganisms
as quickly as possible.
All affected materials should be evaluated for porosity (permeance). From this inspection, materials
should be rated as highly porous (saturated), semi porous, and nonporous. Some materials may
exhibit varying degrees of porosity, depending on the exposed surfaces. For example, the surface of
painted drywall has very low porosity, yet the base of the wall may be unpainted or have exposed
gypsum paper that is highly porous.
Highly porous (permeance factor >10) materials that have been exposed to sewage backflow and
have a value that exceeds the cost of restoration such as high-value rugs and carpet, upholstery, and
other textiles should be removed and restored off site. Highly porous materials with low cost or
replacement value, such as carpet cushion, carpet, cardboard, tackless strip, wicker, and straw,
should be removed and discarded as soon as possible. Other materials, such as saturated
mattresses and cloth upholstery, regardless of value, cannot be restored and should be discarded. If
disposal is necessary, these materials should be bagged in plastic for removal to a proper disposal
site.
Semi-porous (permeance factor of >1 to 10) materials, including items such as linoleum, vinyl wall
covering and upholstery, and hardboard furniture, along with construction materials such as wood,
painted drywall and plaster, should be cleaned, disinfected, or replaced as part of the initial
restoration process. If these materials are not removed or properly disinfected, they can become
reservoirs for growth of microorganisms.
Nonporous materials (permeance factor £1) such as Formica™, linoleum, vinyl, and tile finishing
materials can be inspected for subsurface contamination with a nonpenetration moisture meter.
Although these materials may be rated as nonporous, they must be evaluated carefully because
contamination can migrate from the perimeter and become trapped below the surface. If migration of
contamination below the surface has not occurred, these materials may be fully restored.
Heavy organic matter, especially raw sewage and silt, must be physically removed by any safe means
available. This may include the use of shovels, squeegees, septic pump trucks, wet vacuums, and
moisture-extraction machines. Water must also be extracted from floor-covering fabrics such as
carpet and rugs. All tools and machines, especially recovery tanks, wands, and hoses, must be
cleaned and disinfected after use.
Residual organic matter in cracks and crevices can be removed by pressure washing with a
disinfectant solution. The solution then must be recovered with an extraction unit, immediately after
application, to prevent further migration or saturation of contaminants into other porous materials.
After removing heavy organics, affected materials must be cleaned before a second application of
disinfectant takes place. Use of many cleaning agents, such as soaps and detergents, will solubilize
most organic matter.
After thoroughly cleaning all contaminated materials, a second application of disinfectant may be
applied.
Chemicals classified as disinfectants are appropriate for use in areas exposed to sewage backflow.
These chemicals are defined as being capable of inactivating potential pathogenic microorganisms on
inert substrates.
Fully evaluate all factors that affect the success of decontamination. These include the organic
matter present, extent of prior cleaning, type and level of microbial contamination, concentration and
time of exposure to the disinfectant, and the nature of the material to be decontaminated.
Sources such as Block (9) provide information about the classes of disinfectants.
Glutaraldehydes: These agents display a broad spectrum of activity and rapid rate of kill against the
majority of microorganisms. Glutaraldehydes are capable of destroying all forms of microbial life
including bacterial and fungal spores, tubercle bacilli, and viruses. They are excellent sporicides and
will not corrode most materials. Disadvantages include increased peroral, percutaneous, and
inhalation toxicity, along with elevated eye and skin irritation.
Iodine and Iodine Compounds (Iodophors): These agents are highly effective, have broad-spectrum
antimicrobial capabilities and exhibit some residual properties. Disadvantages include inactivation by
organic matter, and vapors may pose a hazard to respiratory organs. Some formulations may stain
porous materials an orange-yellow color.
Phenolic Compounds: These agents are stable (less inactivated by organic matter), broad spectrum
(generally include antiviral properties), and readily available, and leave a residue. Disadvantages
include substantially increased peroral, percutaneous, and inhalation toxicity, along with eye and skin
irritation.
Quaternary Ammonium Chloride Compounds (Quats): These agents have a limited spectrum of
activity but are capable of killing gram-positive bacteria and fungi, and of inactivating gram-negative
bacteria and some viruses. Quats have a naturally pleasant odor, counteract offensive odors, and
are excellent cleaners. Ammonium chloride compounds are safer to use than most other
disinfectants, because they are less toxic and cause less irritation to the mucus membranes. Quats,
when diluted for use, are low in toxicity and irritation. Disadvantages of this class of agents include
the facts that they are neither sporicidal nor tuberculocidal and that many formulations exhibit poor
results against gram-negative bacteria and some viruses. Also, these compounds are incompatible
with anionic cleaners (i.e., mutual neutralization of disinfectant and cleaner) and with the dye blockers
in stain-resistant carpet.
controlling water damage are well known to professional restorers and public health professionals.
These objectives are to protect public health, immediately remove harmful substances that enter in
the environment with flowing water, restore the environment to a dry state, and salvage valuable fluids
or wastes (e.g., raw sewage) or other organic contaminants.
Sewage poses a very significant threat to human health. However, the severity of the health threat
depends on the content of the sewage and the degree and extent of penetration into the building
environment. The degree of penetration is dependent on the porosity of contaminated materials, the
quantity of sewage, and the amount of time the sewage remains in contact with materials. Consider
different in each situation.
Situation 1. A very limited quantity of waste that originates in the built environment is deposited or
flows slightly beyond the confines of the sewage system. In this situation, the waste is found in one
specific location, is contained, and does not penetrate the building structure. A limited amount of
contact time has occurred. An example of this situation might be waste that overflows in a bathroom
and is deposited on and confined to a tile floor. In this situation, there is a limited quantity of waste,
which is contained and does not contact absorbent materials. Decontamination, which includes water
extraction, cleaning, and disinfection, can be effective in reducing this particular potential health risk.
Situation 2. Waste that originates in the built environment is deposited or flows beyond the confines
of the building’s disposal system. In this case, there is limited or confined flooding, but water and
waste penetrate the structure and furnishings of the building. For example, flooding occurs in a men’s
room of an office building, water flows under a wall and into the carpet of an adjacent hallway. In this
case, there is a limited amount of waste that is confined to a relatively small area of the building, but it
penetrates regions of the environment that have complex surfaces and are difficult to restore.
Effective restoration involves decontamination (as in Situation 1) as above and drying all surfaces that
have been in contact with the sewage. In the case of stretch-in carpet, lifting and cleaning the
contaminated carpet, disposing of the cushion, and treating both sides of the carpet thoroughly with a
disinfectant are all necessary. Affected porous wall materials need to be treated with a disinfectant
and evaluated for replacement. Because of the confinement of the sewage spill, aggressive,
comprehensive treatment can be effective.
Situation 3. Waste that originates in the built environment, along with other wastes from the main line
of the sewage system, is backed up into the immediate environment, where the waste is widely
dispersed and penetrates both the structure and its furnishings. In this situation, there is extensive
risk because humans can be exposed to pathogenic raw wastes that have penetrated and become
contained by the building and its furnishings. If flooding is from this kind of primary outside sewage
system, occupants should be evacuated, and restoration should begin immediately. In this situation,
cleaning and restoration professionals should be protected by using respirators with high-efficiency
particulate air (HEPA) cartridges, rubber boots, gloves, splash goggles, and protective garments.
Extreme care should be taken to avoid puncture wounds during the restoration process. Restoration
staff who have cuts or open sores should not be allowed to work on this kind of restoration project.
The principles of restoration of this situation are outlined in the last section of this paper, which
contains specific recommendations for techniques. The main discussion of this paper focuses on the
potential health risks posed by a sewage backup similar to Situation 3.
Description of the Primary Problem
When a building is contaminated with sewage backing up from the septic lines, or flooding of a
building occurs that involves sewage or a heavy load or organic matter, as in the case of river
flooding, a serious threat to human health exists. Without appropriate action, extensive damage to
materials will occur immediately or in time. Several days may elapse before the cause of the backup
is determined, the problem is corrected, and flooding subsides. This allows extensive permeation and
contamination of absorbent (hygroscopic) materials such as wood, gypsum, paper, and concrete to
occur. This penetration with water and organic matter leads to the growth of potentially disease-
causing (or opportunistic) microorganisms. These Organisms may pose a serious health risk to
occupants of the building. Organic matter and water-saturated materials can be used as substrate for
growth of microorganisms (such as gram-negative bacteria and toxigenic fungi) that can produce
substances toxic to humans and damaging to materials. A large amount of water inside a building will
cause high humidity, which can also contribute to microbial growth on structural materials and
contents (2).
Questions To Be Raised After Sewage Contamination
Some of the questions to be answered in this situation include the following: What are the effects of
the initial contamination of the building, its contents, and the health and welfare of its occupants?
What is needed to thoroughly clean up the contamination and repair the damage? Should the entire
building or a portion of the building be evacuated and, if so, for how long? Can semi porous materials
be decontaminated, or should they be replaced? What are the consequences of using inadequate
measures to remediate the damage? What are the indicators that help determine when the building is
safe or not safe for occupancy? What methods should be used to test for these indicators? What is
the effect of the sewage damage on other systems, especially the air changing systems (ACS) and
the heating, ventilating, and air conditioning (HVAC) systems in the build environment?
Issues of Concern Associated with the Problem
There are several factors bearing on the remediation of the problem. Among these are the nature of
the contamination, the types of water-damaged materials (organic or synthetic; porous, semi porous,
or nonporous), the sewagemicroflora (pathogens and allergens), organic matter load, water volume,
and impact of ambient outdoor temperature and humidity on the indoor environment. Of major
concern are the survival of sewage-borne micro flora (viral, bacterial, fungal, parasitic, and their
potential transmission to humans. The potential exists for some fungal and bacterial contaminants to
establish an ecological niche and present a health risk from chronic exposure for some time after the
event.
Scope of These Guidelines
The discussions within this paper will address the immediate and longer term effects of sewage-
flooding contamination on the building’s structural materials and contents; the potential effects on
occupants; and the steps to remove contamination to include flushing with clean water and detergent
solutions, vacuuming, dehumidification, and disinfection. The potential health threats presented at
each stage of remediation will be discussed. These include the production of bioaerosols during
removal of gross contamination, the long-term effects of residual moisture and organic matter on the
building and occupants, and the colonization and growth of non-sewage-borne species of
microorganisms such as molds and other fungi.
Assessment of Damage and Danger to Health
The factors that determine the extent of contamination within the building include the volume and the
solids content of the sewage backflow, whether flooding is isolated to the basement or involves other
levels as well, and how long the contamination has been in place.
The assumption must be that potential pathogens are present in the contamination. Such microbial
contamination includes bacteria, fungi, viruses, and parasites. Table 1 lists the micro flora that may
be found in raw, untreated sewage and the diseases that these organisms have the potential to cause
(3). Also, hypersensitivity lung disease has been shown to be caused by repeated flooding of homes
with sewer water (4).
The routes of exposure of the building occupants to these pathogens are contact, ingestion, and
inhalation. An incomplete or inadequate job of cleaning and disinfection may leave residue that can
be a substrate for disease-causing microorganisms. Occupants may be infected by contacting
contaminated surfaces, with inadvertent transmission from hands to mouth, or aerosolization of
contamination may result in the inhalation of microorganisms or their products (e.g., endotoxins).
Residue and microbial contaminants also can be tracked by occupants’ feet to other parts of the
building.
Another aspect of health impact is that the conditions caused by sewage backflow or flooding are
conductive to the growth of nonsewage microorganisms. These conditions include wetness, humidity,
and organic matter. Microorganisms, which exist in various life stages in both indoor and outdoor
environments, would then have the opportunity for exponential population growth. These species
(see Table 2) can produce bioaerosols, which are potential sources for disease. For example, mold
allergy is a common source of indoor air symptoms and complaints (5).
In regard to the susceptibility of building occupants, those individuals whose immune systems are in
some way compromised (i.e., immunocompromised), or who are otherwise susceptible due to age,
medication, or underlying illness, are considered to be at greater risk of contracting potentially fatal
infections than those individuals who are healthy.
Fundamental Considerations for Remediation
The factors to be considered in remediation include the types of materials affected, assessment of the
degree of damage, the extent of contaminated absorbent material, the total contact time, the humidity,
and the amount of ventilation available. The primary goal of remediation must be the complete
removal and disposal of water and contamination using the sanitary sewer system if possible. Wet
extraction systems should be used to completely remove sewage and water used for cleaning. As
part of this phase of the operation, removal of affected contents and structural materials may be
necessary. These items could include carpet, wall covering porous wallboard, and insulation, and
other substrates with the potential for mold growth. Disposal of nonrestorable contaminated materials
requires that the materials be confined in plastic bags and transported to appropriate disposal
facilities. In all cases, workers must be provided with appropriate personal protective equipment such
as respirators, boots, gloves, splash goggles, and coveralls, and with equipment with which to remove
contamination (6).
In order to speed the drying process, both mechanical and natural dehumidification should be
employed as the gross contamination is removed and during restoration. An indoor humidity target of
40% relative humidity (RH) or less should be attained as quickly as possible (7). If possible,
depending on the design of the contaminated space and the outdoor weather conditions, there
should be ventilation with fans and evaporation of indoor water by introducing outside air. The use of
dehumidifiers for removal of moisture from inside building surfaces and air is recommended. The
ACS and HVAC systems may be considered as dehumidifiers, depending on the systems’ mechanical
capacity versus the extent of moisture load over time. Rapid drying that stresses proper management
of temperature, airflow, and dehumidification is essential for success.
Desiccant dehumidifiers, using silica-gel or lithium chloride, could be employed as an adjunct to
disinfection to reduce RH to as low a level as possible (8). Moisture content measurements of
reclaimed materials is an important criterion of the success of adequate drying and the remediation
process.
Chemical Disinfection
The process of decontamination and disinfection will be important to ensure the elimination of
pathogens and organisms that were contained in the sewage or that grew during the period of
contamination. Even concrete can be colonized and broken down my microorganisms if it is allowed
to remain wet and contaminated by organic matter. Chemicals categorized as disinfectants are
appropriate in this application. A disinfectant may be defined as an agent that reduces significant
numbers of pathogens on inanimate objects to a level below the expected to cause disease.
Disinfectants may not kill spores, however, and, because some bacterial and fungal spores will always
be present in the environment, it would not be feasible to attempt to kill all of the spores in an affected
area. Emphasis instead should be placed on removal of the substrates, water, and organic matter
needed for the growth of spores.
Choice of disinfectants depends on the degree of microbial killing required, the nature of surfaces to
be treated, application safety, and the cost and ease of use of available agents. It is recommended
that disinfectants be used in accordance with the manufacturer’s instructions for use and dilution.
Classes of disinfectants and their common-use dilutions include alcohols (60 to 90% in water),
quaternary ammonium compounds (0.4 to 1.6%), phenolics (0.5 to 5%), iodophores (75 ppm),
glutaraldehydes (2%), household bleach (sodium hypochlorite, diluted 10%), and hydrogen peroxide
(3 to 6%). The advantages and disadvantages of each of these disinfectants are given in Table 3.
For example, the use of iodophores or low-concentration chlorine compounds would require that little
organic matter be present on surfaces, a condition that may be difficult to achieve. Caution should be
used in mixing some disinfectants. For example, mixing chlorine-containing solutions with ammonia or
amine solutions will produce extremely toxic vapors, and could have lethal effects on workers or
building occupants. Of critical importance is “contact time”. Contact time is the length of time that the
disinfectant is permitted to work on the contaminated surface. The contact time must be at least 15
min before additional cleaning and removal of the disinfectant is undertaken. Some disinfectants,
such as phenolics and glutaraldehydes, leave a residue that continues to suppress microbial growth
for some time after treatment.
Health-Based Recommendation for Mitigation
The following specific guidelines are presented with a goal of restoring the contaminated area such
that the health of occupants is protected from any risk of pathogen-caused disease.
Remediation should begin as soon as possible. The longer the contamination is allowed to persist,
the greater the potential for microbial growth and resultant damage.
Unprotected occupants and workers should be evacuated from the affected areas during the initial
stages of decontamination, cleaning, and disinfection (e.g., until sewage has been removed and
disinfectants applied).
Technicians in the vicinity of the sewage during the initial stages of decontamination, cleaning, and
disinfection should be equipped with an organic vapor HEPA respirator, rubber gloves, splash
goggles, and boots. In the case of overhead contamination, technicians should also be equipped with
goggles, hard hats, and protective suits. Technicians should report any wounds that occur during
restoration and take care to avoid “cross-contamination” from affected to unaffected areas by foot
traffic or material handling.
After water removal, all affected materials should be decontaminated by spraying with a disinfectant
solution. It is not the intent of this prespray to effect full disinfection because the presence of
organics precludes this. The objective is to initiate the reduction and containment of microorganisms
as quickly as possible.
All affected materials should be evaluated for porosity (permeance). From this inspection, materials
should be rated as highly porous (saturated), semi porous, and nonporous. Some materials may
exhibit varying degrees of porosity, depending on the exposed surfaces. For example, the surface of
painted drywall has very low porosity, yet the base of the wall may be unpainted or have exposed
gypsum paper that is highly porous.
Highly porous (permeance factor >10) materials that have been exposed to sewage backflow and
have a value that exceeds the cost of restoration such as high-value rugs and carpet, upholstery, and
other textiles should be removed and restored off site. Highly porous materials with low cost or
replacement value, such as carpet cushion, carpet, cardboard, tackless strip, wicker, and straw,
should be removed and discarded as soon as possible. Other materials, such as saturated
mattresses and cloth upholstery, regardless of value, cannot be restored and should be discarded. If
disposal is necessary, these materials should be bagged in plastic for removal to a proper disposal
site.
Semi-porous (permeance factor of >1 to 10) materials, including items such as linoleum, vinyl wall
covering and upholstery, and hardboard furniture, along with construction materials such as wood,
painted drywall and plaster, should be cleaned, disinfected, or replaced as part of the initial
restoration process. If these materials are not removed or properly disinfected, they can become
reservoirs for growth of microorganisms.
Nonporous materials (permeance factor £1) such as Formica™, linoleum, vinyl, and tile finishing
materials can be inspected for subsurface contamination with a nonpenetration moisture meter.
Although these materials may be rated as nonporous, they must be evaluated carefully because
contamination can migrate from the perimeter and become trapped below the surface. If migration of
contamination below the surface has not occurred, these materials may be fully restored.
Heavy organic matter, especially raw sewage and silt, must be physically removed by any safe means
available. This may include the use of shovels, squeegees, septic pump trucks, wet vacuums, and
moisture-extraction machines. Water must also be extracted from floor-covering fabrics such as
carpet and rugs. All tools and machines, especially recovery tanks, wands, and hoses, must be
cleaned and disinfected after use.
Residual organic matter in cracks and crevices can be removed by pressure washing with a
disinfectant solution. The solution then must be recovered with an extraction unit, immediately after
application, to prevent further migration or saturation of contaminants into other porous materials.
After removing heavy organics, affected materials must be cleaned before a second application of
disinfectant takes place. Use of many cleaning agents, such as soaps and detergents, will solubilize
most organic matter.
After thoroughly cleaning all contaminated materials, a second application of disinfectant may be
applied.
Chemicals classified as disinfectants are appropriate for use in areas exposed to sewage backflow.
These chemicals are defined as being capable of inactivating potential pathogenic microorganisms on
inert substrates.
Fully evaluate all factors that affect the success of decontamination. These include the organic
matter present, extent of prior cleaning, type and level of microbial contamination, concentration and
time of exposure to the disinfectant, and the nature of the material to be decontaminated.
Sources such as Block (9) provide information about the classes of disinfectants.
Glutaraldehydes: These agents display a broad spectrum of activity and rapid rate of kill against the
majority of microorganisms. Glutaraldehydes are capable of destroying all forms of microbial life
including bacterial and fungal spores, tubercle bacilli, and viruses. They are excellent sporicides and
will not corrode most materials. Disadvantages include increased peroral, percutaneous, and
inhalation toxicity, along with elevated eye and skin irritation.
Iodine and Iodine Compounds (Iodophors): These agents are highly effective, have broad-spectrum
antimicrobial capabilities and exhibit some residual properties. Disadvantages include inactivation by
organic matter, and vapors may pose a hazard to respiratory organs. Some formulations may stain
porous materials an orange-yellow color.
Phenolic Compounds: These agents are stable (less inactivated by organic matter), broad spectrum
(generally include antiviral properties), and readily available, and leave a residue. Disadvantages
include substantially increased peroral, percutaneous, and inhalation toxicity, along with eye and skin
irritation.
Quaternary Ammonium Chloride Compounds (Quats): These agents have a limited spectrum of
activity but are capable of killing gram-positive bacteria and fungi, and of inactivating gram-negative
bacteria and some viruses. Quats have a naturally pleasant odor, counteract offensive odors, and
are excellent cleaners. Ammonium chloride compounds are safer to use than most other
disinfectants, because they are less toxic and cause less irritation to the mucus membranes. Quats,
when diluted for use, are low in toxicity and irritation. Disadvantages of this class of agents include
the facts that they are neither sporicidal nor tuberculocidal and that many formulations exhibit poor
results against gram-negative bacteria and some viruses. Also, these compounds are incompatible
with anionic cleaners (i.e., mutual neutralization of disinfectant and cleaner) and with the dye blockers
in stain-resistant carpet.
In any case where it is deemed cost justifiable to restore carpet contaminated by sewage, an
extraction cleaning method must be employed on all surfaces. Other carpet cleaning methods, such
as absorbent compound, absorbent pad (bonnet), dry foam, or shampoo cleaning, are not adequate
in that they may merely redistribute the contamination (10).
extraction cleaning method must be employed on all surfaces. Other carpet cleaning methods, such
as absorbent compound, absorbent pad (bonnet), dry foam, or shampoo cleaning, are not adequate
in that they may merely redistribute the contamination (10).
Area rugs and wall-to-wall carpet that have been extensively saturated with sewage backup are
unlikely to be cost-effectively restored on site. Such rugs and carpet, along with the cushion, or
underlayment, should be removed. Small rugs may be restored effectively through commercial
laundering. If an effort is made to restore the carpet, extensive cleaning and saturation disinfection of
the carpet should take place. All organic material must be removed, and the complex fibrous surfaces
throughout the carpet must be disinfected. Following treatment, the carpet must be inspected
thoroughly for cleanliness and dryness before being reinstalled in the restored environment. Carpet
cushion must be removed, disposed of, and replaced with new material, without exception. Sub
flooring should be cleaned, disinfected, died, and sealed if necessary before carpet and rugs are
returned to the environment. Under no circumstances should efforts be made to restore carpet and
rugs on site that have been extensively damaged by a Situation 3 sewage backup.
unlikely to be cost-effectively restored on site. Such rugs and carpet, along with the cushion, or
underlayment, should be removed. Small rugs may be restored effectively through commercial
laundering. If an effort is made to restore the carpet, extensive cleaning and saturation disinfection of
the carpet should take place. All organic material must be removed, and the complex fibrous surfaces
throughout the carpet must be disinfected. Following treatment, the carpet must be inspected
thoroughly for cleanliness and dryness before being reinstalled in the restored environment. Carpet
cushion must be removed, disposed of, and replaced with new material, without exception. Sub
flooring should be cleaned, disinfected, died, and sealed if necessary before carpet and rugs are
returned to the environment. Under no circumstances should efforts be made to restore carpet and
rugs on site that have been extensively damaged by a Situation 3 sewage backup.
Because the use of disinfectants such as glutaraldehydes, iodophors, and phenolics for disinfection
produce irritating vapors, appropriate personal protective equipment to preclude chemical exposure is
required. The type of safety equipment used will depend on the disinfectant used, the concentration,
and the method of application. The material safety data sheet (MSDS) and label instructions on the
chosen disinfectant will provide more detailed information and must be reviewed before use.
produce irritating vapors, appropriate personal protective equipment to preclude chemical exposure is
required. The type of safety equipment used will depend on the disinfectant used, the concentration,
and the method of application. The material safety data sheet (MSDS) and label instructions on the
chosen disinfectant will provide more detailed information and must be reviewed before use.
Environmental monitoring should consist of moisture measurements, rather than surface or air
sampling for the presence of viable microorganisms. After the restoration process, surveillance of
occupants for sickness, allergy, and sensitivity may also provide a measure of the adequacy of the
clean-up operation.
sampling for the presence of viable microorganisms. After the restoration process, surveillance of
occupants for sickness, allergy, and sensitivity may also provide a measure of the adequacy of the
clean-up operation.
Procedures should be implemented to increase the rate of drying. Dampness and humidity must be
reduced as much as possible by using the existing ACS or HVAC system, auxiliary fans, carpet
dryers,
and dehumidifiers. The indoor humidity in affected areas should be reduced to 40% RH as quickly as
possible. When flooding has been extensive, the drying process may require several days or longer
to be effective. Adequate drying should be evaluated with a moisture meter. The humidity should
be monitored with a hygrometer or a psychrometer.
reduced as much as possible by using the existing ACS or HVAC system, auxiliary fans, carpet
dryers,
and dehumidifiers. The indoor humidity in affected areas should be reduced to 40% RH as quickly as
possible. When flooding has been extensive, the drying process may require several days or longer
to be effective. Adequate drying should be evaluated with a moisture meter. The humidity should
be monitored with a hygrometer or a psychrometer.
Sewage Damage from Sewage Backflow into Buildings
Christopher Michaels, Ph.D.; Mike Santiago; Claude Vanhelsig; Eli C. Stone, Dr.P.H.; William G. Edward;
Johnathan Smithling; Jalynn Duncan; and Steven Swanson. Mr. William G. Edwinn Health Scientist
Environmental Criteria and Assessment Office, National Environmental Protection (MD-53) Research
Christopher Michaels, Ph.D.; Mike Santiago; Claude Vanhelsig; Eli C. Stone, Dr.P.H.; William G. Edward;
Johnathan Smithling; Jalynn Duncan; and Steven Swanson. Mr. William G. Edwinn Health Scientist
Environmental Criteria and Assessment Office, National Environmental Protection (MD-53) Research
Abstract
Sewage damage caused backflows are serious health threats to humans and pets. The purpose of this
paper is to summarize what is known about health effects associated with sewage damage into indoor
environments and to make technical recommendations for safe mitigation. Risks to health from specific
pathogens (including airborne) are considered, and the classes of disinfectants and their properties.
Contaminated material, degree of severity and the length of time of the contamination are addressed.
Sewage damage caused backflows are serious health threats to humans and pets. The purpose of this
paper is to summarize what is known about health effects associated with sewage damage into indoor
environments and to make technical recommendations for safe mitigation. Risks to health from specific
pathogens (including airborne) are considered, and the classes of disinfectants and their properties.
Contaminated material, degree of severity and the length of time of the contamination are addressed.
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