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What are Endotoxins and Exotoxins and where do they come from?

The word “toxin” causes my ears and eyes to perk up, because these are the types of substances that cause illness and even death.  Thankfully, it is increasingly possible to avoid toxins by understanding where they live and how they’re spread.   Science is advancing very rapidly to show us how to manage our environments, food, lifestyle and even our bodies to live more healthfully.   Endotoxins come from Gram-negative bacteria, and Exotoxins can come from either Gram-positive or -negative bacteria so we’ll start with what the “Gram” test means. 

Bacteria can be classed into two different groups: “Gram-negative” or “Gram-positive”.  These classes are based on a test developed by scientist Chritian Gram in 1884, which differentiates the bacteria using a purple stain.   According to webmd.com, bacteria either have a hard, outer shell, or a thick, mesh-like membrane called peptidoglycan.  The hard outer shell will resist the purple stain, and show up as a red color.  These are called “gram negative” because the purple stain did not show.  Bacteria with the peptidoglycan absorb the purple stain much more easily and are called “gram positive”.  The stain also tells more characteristics about the bacteria and the way it interacts with treatment. 

The peptidoglycan layer of Gram-negative bacteria is much thinner than that of gram-positive bacilli; instead Gram-negative have a hard, protective outer shell, making them harder to kill because of their harder cell wall.  When their cell wall is disturbed, or the bacteria are dead or dying, gram-negative bacteria release endotoxins that can make symptoms of illness worse.  In contrast, exotoxins are produced inside the bacteria and may be released while the bacteria cell is living, or during its death.

Here is a diagram that shows how the exo- and endo-toxins are released (source: microbiologyinfo.com).  (I distinguish them by remembering that endotoxins are only emitted at the “end” of life of the bacteria):

Here are some examples of gram-negative bacteria diseases (webmd.com):

• Vibrio cholerae (Cholera, a serious intestinal infection)
• E. coli (E. Coli infection)
• Yersinia pestis (Plague, an infection of the lymph nodes and lungs)
•  Bartonella henselae (Cat-scratch disease)
• H. Pylori (gastritis, peptic ulcer disease, gastric lymphoma, and gastric cancer)
• Campylobacter (campylobacteriosis, an infection that usually affects the digestive tract)
• Legionella bacteria (Legionnaire's disease, a lung infection)
• Salmonella (salmonellosis, a digestive infection caused by contaminated food)

Here are some Gram-positive bacteria (and the infections they cause): 

• Staphylococcus aureus (MRSA, toxic shock)
• Streptococcus group A (strep throat, toxic shock)
• Clostridium botulinum (botulism)
• Bacillus anthracis (Anthrax) 

As you can see, endotoxins and exotoxins are a serious matter!  Here are some of the other important differences between them (byjus.com):

(A toxoid is a chemically modified toxin from a pathogenic microorganism, which is no longer toxic but is still antigenic and can be used as a vaccine (Oxford languages).)

There is so much to study about bacteria, however since we at HypoAir mainly focus on air quality, we’ll try to limit this post to the toxins that can be transmitted through the air.  

Endotoxins (source: buildequinox.com, manufacturer of the CERV Energy Recovery Ventilator in Urbana, Illinois):

• Are pyrogens, that is, they often cause a pyrogenic reaction (fever).
• Cause fatigue, a common characteristic of sick building syndrome. 
• Don’t produce immunity, but only a temporary resistance known as “Monday fever”. Workers in industries with significant endotoxin levels have been found to be most afflicted on Monday, with reduced effects through the week. Endotoxin resistance is lost over the weekend, with the illness beginning anew the following Monday [5]
• Are “adjuvant”, meaning that they can amplify the effects of other harmful substances. 
• Are associated with sepsis, an extreme immune response by the body that often ends in death.  
• The presence of pets in indoor spaces can represent an important source of air contamination and can be linked with the level of indoor endotoxins. The presence of dogs and cats can be the main predictors of endotoxin levels in house dust [1, 4-7]. Other predictors are the presence of vermin, such as mice, and infrequent cleaning, which indicates poor hygienic conditions in the home [1]. Storage of organic household waste indoors also increases bacterial contamination in the indoor environment [1]. (intechopen.com)

How can we reduce exposure to endotoxins?

• Reduce Dust: According to EMLab, a commercial IAQ laboratory in North America, “ Endotoxin exposures are mainly through the air.”  “Endotoxins do not float freely, but instead are attracted to dust particles. Reduction of dust is essential for controlling endotoxin levels. Dust reduction requires both fresh air filtration and filtered air recirculation. Continuous, low flow fresh air ventilation systems without recirculation do not effectively manage indoor particulates. Endotoxin levels and dust levels are not strongly correlated indicating that they come from independent sources. A single dust particle in the 2 to 10 micron range has sufficient surface area to hold a million or more endotoxin molecules (approximately 0.1ng of endotoxin). Therefore, reduction of dust is important regardless of whether one lives in a dusty or relatively dust-free environment.” (this and following points from buildequinox.com).
• Removal of food sources: “Coupled with proper ventilation is reduction of source generation of endotoxins. In the home environment, it is clear that kitchens are one source of endotoxin generation. Removal of food wastes and standing dishwater will reduce bacterial growth with subsequent production of endotoxins. Even a bowl of standing water will grow bacteria in a home. Bacteria and nutrients are ubiquitous indoors and outdoors, and they will land in water or moist regions where bacterial growth will occur.” Kitchens have the highest level of endotoxins, followed by living rooms and bedrooms.
• Avoid use of misting humidifiers: “Cold temperature (misting) humidifiers are strongly linked to high endotoxin levels. Vaporizing humidifiers that heat water to boiling have not been found to produce high levels of endotoxins.” An alternative method for achieving sanitized, cold temperature humidification in a home is through plant transpiration. Plants can reduce toxins in homes [12]. The plant-root matrix releases sanitized water into the air (assuming proper plant care that does not form a wet mass promoting fungal and bacterial growth).

Exotoxins are (from textbookofbacteriology.net unless otherwise noted)

• part of a defensive system of bacteria to avoid capture and killing by leucocytes (part of our body’s immune system). (sciencedirect.com)
• Produced by both Gram-negative and Gram-positive bacteria 
• More highly poisonous by mass than endotoxins, strychnine, or snake venom 
• Can be “super-antigenic” or cause stimulation to the immune system 
• are often encoded by mobile genetic elements, including bacteriophage (phage). Phage can transfer genetic information to the bacteria they infect. (study)
• Can produce illness even when the microbes that produced them have been killed. (skybrary.aero)

What are the sources of exotoxins? (from intechopen.com)

• Actinobacteria (especially Streptomycetes), Bacillus species and various other bacteria grow in moist building materials together with fungi. Elements from bacterial structures released in air include bacterial cells, bacterial spores, peptidoglycans, microbial volatile organic compounds, exotoxins, and other bacteria growing metabolites.
• Gram-positive bacteria with exo- and endospores like Streptomyces and Bacillus can grow on moist building materials. Their spores are very resistant and can survive even if the air humidity is low.
• Humans are an important source of indoor bacteria. The upmost layer of the normal human skin is continuously renewed, and skin scales containing bacteria are shed into the environment. Bacteria in the respiratory airways are eliminated through Pflügge droplets while talking, coughing, or sneezing. The level of air contamination is dependent on the number of persons inside a room and the efficiency of the ventilation system (natural or artificial ventilation). Bacteria that can be identified in indoor air are micrococci, staphylococci, streptococci, and corynebacteria.

How can we reduce exotoxin exposure?

• Maintain your home so that there are no active leaks and humidity stays between 40-60%.  This will reduce actinobacteria that produce exotoxins.
• Practice good hygiene by covering your mouth and nose while coughing or sneezing.  This reduces the amount of small particles in the air that can contain bacteria and exotoxins.  Dispose of tissues in the trash and wash hands with soap and water. 
• According to the WHO, if exposure to the toxin via aerosol inhalation is suspected, additional exposure to the patient and others must be prevented. The patient's clothing must be removed and stored in plastic bags until it can be washed thoroughly with soap and water. The patient should shower and be decontaminated immediately. 
• Most exotoxins can be destroyed by heating, (wikidoc.org), so eating thoroughly cooked food often eliminates the danger of ingesting the exotoxin. The WHO recommends these five strategies in food safety:
  • keep clean
  • separate raw and cooked
  • cook thoroughly
  • keep food at safe temperatures
  • use safe water and raw materials.

Use of a HEPA filter can reduce aerosols and fine particles containing bacteria, endotoxins and exotoxins, although some of the smaller phages may slip through.  This is where a healthy immune system and abstaining from smoking pick up.  Cigarette smoking is a substantial risk factor for important bacterial and viral infections. For example, smokers incur a 2- to 4-fold increased risk of invasive pneumococcal disease. (2004 study).  In addition, exposure to cigarette smoke causes MRSA bacteria (just one bacteria studied) to become even more resistant to killing by the immune system. (UCSanDiego Health News)  Of course, smoking through a dirty water pipe (bong) is inviting disaster!  Here are the details (mooselabs.us):

Bacteria, endotoxins and exotoxins are all around us (and even in us), but with good judgment and  precautions, you can avoid being one of the infection statistics!

Do Air Purifiers in Classrooms Reduce Illness?

Ahh, this is certainly one time when I’m glad to be working remotely!  As my co-workers send their children back to school, the illnesses (from the common cold to COVID-19) ramp up again in their families as germs get passed back and forth in classrooms.

In 2021, there was a lot of discussion about how to keep students and teachers safe from COVID-19.  Many school districts rushed out to purchase and install air purifiers, with ensuing debate on which purifiers were effective, or in fact, which were dangerous.  It can be a bit confusing, so I headed online to find studies on what works.  I found that across a wide spectrum of experts, the following three solutions to reducing illness and increasing classroom performance are, in order, 

1. Fresh air ventilation

2. HVAC system filter maintenance

3. Air purifiers

This list really is in order of importance.  First of all, air purification technology is great, but we at HypoAir are always in favor of the most natural option first, one that replicates the outdoors, and that will be fresh air VENTILATION.  That’s right, you can put an air purifier in a classroom, but without a continual supply of fresh air to increase oxygen and dilute rising CO2 and virus and bacteria levels, the air purifier can only do so much.  Fresh air can be supplied through an open window if the weather or outdoor air quality is nice, but there should be fresh air ventilation built into every HVAC system so that air quality outside doesn’t limit the quality of air indoors.  Many buildings in the U.S., especially schools, do not meet recommended ventilation rates. The quantity of ventilation depends on how many people are in the room; it should be 15 cubic feet per minute per person. In one study coauthored by Rengie Chan, a research scientist at Lawrence Berkeley National Labs, 85 percent of the California classrooms included failed to meet the minimum standard of 15 CFM per person. Other studies show many American classrooms have an average ventilation rate of only 6 to 11 cfm per person.(wired.com). 

The problem with estimating actual fresh-air ventilation to a room by HVAC is that unless there is an intake from the outside in the system, air blown into the classroom is just being recirculated through the ducts and maybe only filtered once, not adding any fresh air at all.  This type of estimation requires a person knowledgeable about the building’s HVAC system.  If fresh air intake is included, then one expert (Joseph Allen, a professor at Harvard’s School of Public Health) estimates that for reducing Covid-19 risk, the air in the room should be completely replaced at least five times an hour. In a Boston school, the sensor registered about 400 cfm of fresh air coming in through the unit ventilator in one classroom. The room measured 1,010 square feet and had 9.5 foot ceilings: It had 9,595 cubic feet of air. Multiply 400 cubic feet per minute by 60 minutes, divide it by the volume, and you find that the air only gets turned over 2.5 times an hour, which was not sufficient. (wired.com)  However, when conducting another experiment in the same school, they found they could boost air changes to 17 to 20 air changes per hour by opening windows and doors.

An easier way to determine if ventilation is sufficient is by monitoring the CO2 level.  To demonstrate the effect of reducing CO2 levels on disease transmission,  researchers in Taiwan reported on the effect of ventilation on a tuberculosis outbreak at Taipei University. Many of the rooms in the school were underventilated and had CO2 levels above 3,000 ppm. When engineers improved air circulation and got CO2 levels under 600 ppm, the outbreak completely stopped. According to the research, the increase in ventilation was responsible for 97% of the decrease in transmission.(theconversation.com)

Since the coronavirus is spread through the air, higher CO2 levels in a room likely mean there is a higher chance of transmission if an infected person is inside. Based on the study above, experts recommend trying to keep the CO2 levels below 600 ppm. You can buy good CO2 meters for less than $100 online (check out our post including them); just make sure that they are accurate to within 50 ppm. (theconversation.com) What can it hurt to donate (or get together with other parents to donate) several CO2 sensors with remote readings, in order to check the levels of CO2 in your childrens’ classrooms?  

After fresh-air ventilation has been established, let’s look at air cleaning.  In any HVAC system, there should be at least filters in the air returns and they should be changed regularly.  By increasing the MERV rating on these filters to MERV 13, smaller particles like viruses can be filtered out to reduce illness transmission rates.  Changing the rating of the filters should be done in cooperation with the facilities manager in order not to overload the HVAC system, but it is quite possible even if filter box sizes need to be enlarged (see our post on Air Filter Thickness for how to increase MERV rating without increasing pressure drop). 

Third, air purifiers can be considered.  If the school has done what they can to provide adequate ventilation and HVAC filter maintenance, then air purifiers can add another layer of protection by filtering or killing the germs that get by these first two conditions.  In order to be effective, an air purifier must either:

• pull all of the air in the room through a filter unit several times an hour, OR

• Send out a non-toxic disinfectant that disperses to all areas of the room.

The first of these can be accomplished with units that include high-powered fans, but these can be noisy.  Noise in a classroom, just like in your home, can be distracting and debilitating for the teacher and students!  For this reason, air purifiers that depend upon air throughput for efficacy need to be evaluated for noise when running at the optimum fan speed for the size of classroom considered.  Also, replacement parts such as filters need to be considered in the total cost.  The cost of a HEPA filter (and possibly UV lamp) for every purifier, for example, can quickly add up to thousands of dollars a year when changes are needed in a school with dozens of classrooms.  Maintenance of these units will fall on the school’s facilities staff, who are likely already over-burdened with an increased cleaning schedule.  

The second option is one that HypoAir promotes because it really is akin to what goes on naturally outdoors.  Ions are one of nature’s cleaning devices, because positive and negative ions are continually floating through the air and reacting with allergens, viruses and bacteria, deactivating them.  These ions are naturally produced by natural phenomena in the air such as sunshine, lightning, crashing water like at the seashore or a waterfall, and plants.  Indoors, we produce them by passing a small electrical charge through stainless steel “needles” to produce positive and negative ions, which get distributed through the air to every part of the room (like adding drops of dye to clean water, soon every part of the water is changed!).  This is done nearly silently, because powerful fans are not required for distribution (any fans already in use in the room will boost circulation of the unit’s small fan).  In addition, maintenance on HypoAir ionizers is virtually nil, because no filters are required and there are no replacement parts.  The cost of running our ionizers is very small, as they use minimal electricity. 

So what about real world testing of these methods?  The CDC released a study on 123 elementary schools in Georgia in 2021.  The schools included did one of three things:

1. Nothing

2. Increased ventilation by opening doors, windows or using fans 

3. Added HEPA filters to classrooms.

In schools that improved ventilation through dilution methods alone, COVID-19 incidence was 35% lower than the schools that did nothing, whereas in schools that combined dilution methods with filtration, incidence was 48% lower than the schools that did nothing.  The takeaway here is that ventilation and HEPA filtration work, even with some added cost for ventilation modification or filter replacements!  Doing nothing, on the other hand, increases the cost of lost school days, makeup time and medical costs for students and teachers substantially.   

It’s a new world with viruses and allergens challenging young and old alike everywhere, but the wisdom of fresh-air ventilation combined with the technology of purification can make it significantly easier to bear!

Fiberglass: the air quality problem you didn’t consider

With extreme weather issues such as storms and fires in the news, we can become very focused on mold from water damage and particulate matter (PM) from air pollution like smoke, but another problem has been silently causing lung and whole-body issues for decades: fiberglass insulation.

Fiberglass insulation, also known as glass wool, was accidentally invented in the 1930’s and patented in 1938 as Fiberglas.  It became a popular insulation for building and comes in batts, with a paper or plastic backing, or is available in loose form in bags, that can be blown into place.  Now fiberglass is used in: 

• Appliances like dishwashers, refrigerators, ovens, exhaust fans, clothes dryers
• Kerosene heaters and wood-burning stoves
• roof shingles
• Beds (also known as a silica sock)
• Cigarette filters
• HEPA and HVAC filters
• Light fixtures
• Carpets
• Packing tape
• And even some brands of toothpaste!

Children may be especially vulnerable to potential effects from fiberglass particle inhalation. “We’ve seen a substantial increase in air quality concerns from homeowners with young children experiencing chronic cough and eye irritation,” says Jeffrey Bradley, president of IndoorDoctor LLC. Bradley says fiberglass is often the culprit. (iqair.com)

Like most materials, fiberglass insulation degrades over time, and water speeds up the degradation process.  Therefore, although blown-in insulation is a popular choice for insulating attics and walls, leaving fiberglass exposed to humid air can cause the fibers to break and become airborne.  Typically, most manufacturers warn about wearing masks if you manually “disturb” the insulation by pushing past it or cutting into it.  However, loose fiberglass that is exposed to air currents can pick up these small fibers without manual disturbance, resulting in unhealthy PM2.5 levels in homes where it gets entrained into the air conditioning system.  

One woman has detailed her family’s project to remove all the fiberglass from their house after it was determined that fiberglass dust was making her sick.  Fiberglassawareness.com is a very useful website with many photos of where fiberglass is used in homes, and even cars and other buildings where you may not suspect it.  That pink (or yellow or white or green) stuff that you thought remained in the attic, doesn’t always stay where it belongs!  Wherever you can see exposed fiberglass, it may be emitting small particles into the air.  That means if it is peeking out of the ends of wrapped ducts, or falling (sometimes imperceptibly) out of can light fixtures, or being sucked into your AC system through small leaks in the ducts, it is in the air you breathe and can cause a myriad of health issues.  This page details a long list of fiberglass-exposure symptoms which overlap with mold-exposure symptoms, fibromyalgia symptoms, and auto-immune disorder symptoms, so the main culprit can be hard to diagnose.  In addition, many fiberglass insulation products use:

• Phenol formaldehyde to bind the fiberglass fibers together (iqair.com), and the off-gassing of formaldehyde can cause similar symptoms. Formaldehyde is a carcinogen and exposure to fiberglass insulation formaldehyde causes brain cancer. According to John D. Spengler et.al., in the "Indoor Air Quality Handbook," residents of mobile homes who are exposed to fiberglass insulation are at increased risk of brain cancer. 
• Styrene or Vinyl-Benzene is found in fiberglass insulation, and because benzene is used in many home other consumer products like water bottles, convenience food trays and wrappers, and feminine products, it contributes to a thick low-lying VOC cloud in some homes. According to Teresa Holler in the book "Holler for Your Health," styrene is toxic to the nervous system and exposure to styrene in fiberglass insulation causes behavioral changes, concentration problems, depression, tiredness, headaches, memory problems and weakness.  According to Andre E. Baert in the book "Biomedical and Health Research," long-term exposure to styrene in fiberglass insulation causes brain tumors and cancer. (ehow.com)
• Methyl-ethyl-ketone (MEK) is used as a binder in some fiberglass.  Nick H. Proctor et.al., in the book "Proctor and Hughes' Chemical Hazards of the Workplace," list methyl ethyl ketone as a neurotoxin and exposure to MEK in fiberglass insulation as a cause for dizziness, nausea, headaches, depression and unconsciousness. (ehow.com)

According to the California Department of Public Health, frequent exposure to fiberglass insulation causes permanent changes in the central nervous system, the symptoms of which include personality changes, poor coordination, fatigue and poor concentration.(ehow.com)

How do you get rid of fiberglass in the air?  In some cases “encapsulation” can be an answer, which means that you can add a layer of protection over it.  We should never see exposed fiberglass (the brown paper side is supposed to be installed on the “warm” side, which in southern climates leaves the fiberglass exposed to the inside of the attic).  This real estate inspector wrote an article on encapsulation from the point of view that fiberglass is a poor air barrier and therefore should have a proper air barrier on both sides.  However, he notes at the end that a homeowner should not try to encapsulate any fiberglass himself, because of the risk of causing mold if moisture cannot escape.  

Here’s how you can minimize your exposure to fiberglass: 

• Repair damaged sections of fiberglass insulation with proper foil duct tape.
• If you have blown-in fiberglass in your attic or walls, seal all penetrations such as ceiling fixtures, wire and plumbing penetrations, light switches, and cracks in drywall
• Check the internal condition of any “duct board” ducts or ducts internally insulated with fiberglass.  Unfortunately these degrade over time and cause the fibers to become entrained in the air.
• If your health issues have not resolved, consider removing some or all of the fiberglass that could be causing them. 
• Replace fiberglass insulation with ducts that are insulated with air bubble wrap, and walls and ceiling insulation with spray foam or cellulose insulation (however, be aware that cellulose insulation is treated with fire retardants to make it safe, which can cause other health issues to those who are sensitive). (nachi.org)

If you know or suspect that your health problems are being caused by fiberglass or VOCs that come from the fiberglass, keep a journal of how you feel during the day at different times, including where you are, what you are doing,  if the building’s HVAC is running, what you are wearing, eating, working with, etc.  It’s possible that you can find the link by putting the pieces together from your experiences, and from others’ experiences.  Research sites of others with environmental and chemical sensitivities, such as Fiberglassawareness.com, mychemicalfreehouse.net, and nontoxicforhealth.com (the latter two have a lot of scientific research on them), and don’t give up!