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Indoor Exposure to Endotoxins …A Health Hazard

The main source of endotoxin contamination in indoor environments is the result of infestation of Gram-negative bacteria. The sources of Gram-negative bacteria in a closed environment may include water intrusion, condensation in air conditioning units, cooling towers, humidifiers, organic dust, biofilms in toilets and in bathrooms, and other microbial materials.

Clearwater 4/26/2012 9:23:21 PM

Out of various indoor contaminants, bacterial endotoxin may illicit significant health and hygiene effects.  The bacterial endotoxin is a biochemical substance composed of a protein, lipid, and polysaccharide molecule known as LPS (Lipopolysaccharide) and/or LOS (Lipooligosaccharide) and is generally found in the outer membrane of Gram-negative bacteria.  These substances are released into the ambient environment after the lysis of the bacterial cell wall, which contains them. Some Gram-positive bacteria such as Listeria monocytogenes may also produce an endotoxin-like substance.

Indoor Environment and Endotoxin

The main source of endotoxin contamination in indoor environments is the result of infestation of Gram-negative bacteria.  The sources of Gram-negative bacteria in a closed environment may include water intrusion, condensation in air conditioning units, cooling towers, humidifiers, organic dust, biofilms in toilets and in bathrooms, and other microbial materials.  The common Gram-negative bacteria of indoor environments that may produce endotoxin are, but are not limited to the species of: Pseudomonas, Alcaligenes, Citrobacter, Escherichia, Klebsiella, Vibrio, Salmonella, Haemophilus, Shigella, Neisseria, Bordetella, etc.  

Endotoxin Levels in Indoor Environments

There is no universally accepted guideline for endotoxin in indoor environments.  The concentrations of endotoxins in the indoor environment range from a few to several thousand endotoxin units per milligram of house dust as per a report by the WHO.  In the United States, an average background level of endotoxin is generally below 1 EU/m3.  According to a report by the Natural Resources Defense Council, the average indoor endotoxin concentration of 5.9 EU/m3 was recorded from the New Orleans community in 2005.  However, the health effects due to endotoxin may vary from individual to individual depending upon immunity and other factors. Exposure to endotoxin levels with 28 EU/m3 may cause long term health effects.

Health and Hygiene Effects of Endotoxins

Water damage and dampness problems in a building may lead to the presence of endotoxin.  Endotoxin can also be associated with BRS (Building Related Symptoms).  The endotoxin inhalation has been implicated in organic dust toxic syndrome, bysinnosis, and illness in agriculture-confined workers, such as swine-confinement.  This toxin may cause powerful inflammatory reactions in humans with flu-like symptoms, fever, cough, headaches, and respiratory distress.  The inhalation exposure of endotoxin is linked to the increased risk of respiratory infections, airway inflammation, asthma attacks, chronic bronchitis and hypersensitivity pneumonitis.  Chronic obstructive pulmonary disease (COPD) in workers is also linked to endotoxin exposure.  Basically, with this condition the function of the lungs drops down and is irreversible.  Lung function drops down even with a short exposure of an endotoxin level of 45 EU/m3.  Endotoxin may also cause endotoxemia in humans, which can lead to septic shock in cases where the immune response is severely pronounced.

Environmental Sampling for Endotoxin Tests

Air, fluid, and bulk samples can be collected from indoor environments for endotoxin tests.  All the collection devices shall be free from endotoxin or the material that binds with endotoxin.  During the time of sample collection, PPE (Personal Protective Equipment) is essential and highly recommended to prevent the cross-contamination, as well as endotoxin exposure to the technician or the person collecting the sample. The collected samples should be stored desiccated wherever possible or stored at 4° C.

  • Air sampling: Air samples may be collected by using a low volume pump that has been calibrated to 1.5 liters per minute for four hours by drawing the air through a tubing free on an endotoxin-free polystyrene cassettes with 37mm diameter 0.2 µm polycarbonate membrane filters and AP40 glass-fiber backing pads.  
  • Fluid sampling: Collect a portion of suspected fluid (up to 100 ml) in a glass or polystyrene container that is free from endotoxin.
  • Bulk sampling: By using the aseptic technique, collect the suspected bulk material and place it into a polystyrene bags that is free from endotoxin.  A gauze or swab (made out of sterile endotoxin-free material) sample may also be collected for testing.  Wipe or swab approximately 6” x 6” area by covering horizontally and vertically.  Endotoxin-free water can also be used to moisten the sampling media for an effective collection.

It is highly encouraged and recommended to collect the blank samples for quality control as well as for test validation.  

Endotoxin Testing  

The detection of endotoxin in an environmental sample is performed based on a biochemical reaction known as lysate coagulation.  Limulus blood is used as a supply of pure lystate that is extremely sensitive to endotoxin.  In the presence of endotoxin the coagulation reaction happens.  The Environmental Diagnostics Laboratory (EDLab) uses the LAL method as described above for endotoxin detection. 

Removal of Endotoxin from Indoor Environments

Endotoxin removal from the indoor environment is not an easy task.  A scope of work for endotoxin removal requires information about the contaminated place which includes, but is not limited to, biological, a-biological and environmental factors.  Since the endotoxin is a heat stable compound, its breakdown is not easily accomplished with simple steam cleaning techniques.  Results of chemical remediation of endotoxin are not well established.  Green technology is often recommended for the remediation of endotoxin as it has minimal residual or environmental impact. 

For environmental cleaning of endotoxins in evaporator coils and AHU’s the best way for treatment is the Pure-Steam Coil Cleaning process a green technology.  For cleaning of contaminated furnishings, clothing, belongings, etc.. may be treated with HEPA cleaning and sanitizing with nano-molecular treatments.

DIY Test Kits or Hiring an IEQ Professional:

Your potential home or office IEQ can be evaluated for endotoxins and/or by using a number of testing methods.  These samples can be collected by “do-it-yourself” test kits or by hiring an IEQ professional. All the collected samples should be sent to a qualified, AIHA accredited laboratory for the analysis.  The results obtained can efficiently be used for managing the concerned environment.

A more comprehensive environmental assessment can also be performed by a specialized, credentialed professional indoor environmental consultant. Call the pros at Pure Air Control services-Building Sciences team at800-422-7873, Ext. 802 to discuss your next IEQ project.

About Environmental Diagnostics Laboratory (EDLab):

Established in 1994, Environmental Diagnostics Laboratory (EDLab) is the industry leader of indoor environmental laboratory analytics under the direction of Dr. Rajiv Sahay, FAIS, CIAQP

The parent company, Pure Air Control Services is a international environmental firm performing the following IAQ services: Building Sciences Evaluation; Building Health Check; EDLab an AIHA accredited Environmental Microbiology Laboratory, Environmental Project Management; and Mold Remediation Services, among other indoor environmental services.

The company’s expanding client roster includes: FAA, USACE, General Services Administration (GSA); Allstate Insurance; Carrier Air Conditioning; Naval Air Warfare Center, Orlando; and Naval Air Station - King's Bay, Georgia, Walt Disney World, and many other Fortune 500 companies, school boards, and city, state, and county governments, making Pure Air Control Services the reliable industry leader in IAQ.

For more information on EDLab, Pure Air Control Services, Inc. please contact Dr. Rajiv Sahay or Alan Wozniak at (800) 422-7873, or visit


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