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Which is a healthier home habitat: the forest or the desert?

Which is a healthier home habitat: the forest or the desert?

Is it more healthy to live in or near a forest or a desert?  Spoiler alert: we’re not going to call that decision.  Each habitat has its advantages and disadvantages, so we’ll explore them to see which one is best for you.

You might think that these two climes are extremely opposite, but they do have (at least) one thing in common: trees!  Granted, there are many more trees in forests, but trees in the desert can accomplish many of the same purposes.  In a 2020 study, one particular type of tree found in Qatar (desert region), Acacia tortilis, was found to be the most efficient tree species for reducing air pollution, having good capacity to intercept storm water runoff, reducing energy consumption and reducing air pollution levels through dry deposition, avoiding further pollution formation and CO2 removal.  Mature trees (with diameter greater than 45 inches) were much more efficient at accomplishing these goals than younger trees (diameter 10 inches). 

According to the US Department of Agriculture (USDA), trees provide many benefits, including the ability to clean our atmospheric environment both directly underneath their canopies, and at a larger, regional scale. Because leaves transpire large amounts of moisture, trees have a cooling effect on the surrounding environment—like air conditioning. By cooling and cleansing the atmosphere, trees help to make air safer for breathing by plants, animals, and humans and have positive benefits on habitat. In fact, air quality underneath a closed tree canopy is often significantly better than above that tree canopy, especially for ozone—a common air pollutant that forms downwind of urban air pollution sources. On a regional scale, forests also scrub ozone and other nitrogen and sulfur-containing air pollutants out of the prevailing winds, protecting more sensitive areas.  Healthy forests with large, widely-spaced trees also protect from wildfire smoke because pines and other fire-adapted trees with their thick, fire retardant bark better resist fire in all but the most extremely hot, dry, and windy conditions.

Interestingly, some trees contribute to ozone production, while others reduce it.  This is because species like black locust, European oak and poplar intensively emit isoprene, which results in higher ozone and PM10 concentrations, while tree species emitting primarily monoterpenes such as beech, magnolia and wayfaring trees yield less of both.  (Impact of vegetative emissions on urban ozone and biogenic secondary organic aerosol: Box model study for Berlin, Germany)

Another common denominator between forests and deserts is animals–whether they are domesticated or wild, contact with animals is more frequent in remote areas than in urban areas.  There is also much research that shows how exposure to animals benefits us.  In one study, the researchers recruited 2 groups of young men:  20 young men who were raised for the first 15 years of life on farms with farm animals, and a second group of 20 young men who were raised for the first 15 years of life in a city of over 100,000 people, without daily exposure to pets. Both groups were then given Trier Social Stress Test (TSST), a model of acute psychosocial stress in humans. The results revealed that those who grew up in cities without daily exposure to pets, and thus lacked exposure to diverse microbial environments during childhood, responded to psychosocial stress with exaggerated inflammation markers,  (Less immune activation following social stress in rural vs. urban participants raised with regular or no animal contact, respectively)

Now, let’s talk about some specifics of each habitat.


Although the stereotypical desert is hot, dry and sandy, only one of these words accurately describes every desert (dry).  Most experts agree that a desert is an area of land that receives no more than 25 centimeters (10 inches) of precipitation a year. The amount of evaporation in a desert often greatly exceeds the annual rainfall. Surprisingly, areas near water can actually be deserts, because humidity in the air doesn’t predict or cause rainfall.  The Atacama Desert, on the Pacific shores of Chile, is a coastal desert. Some areas of the Atacama are often covered by fog. But the region can go decades without rainfall. In fact, the Atacama Desert is the driest place on Earth, and some weather stations in the Atacama have never recorded a drop of rain.  (Desert)

Low humidity is obviously a benefit to keeping mold from growing on outdoor or indoor surfaces, if air conditioning is not needed.  Dryness would lead some to believe that mold could not be a problem in the desert.  However, mold spores are present everywhere, and lack of home maintenance can allow even a small amount of rainfall to turn into a mold disaster.  Mold can start growing undetected in attics, crawlspaces and walls during one of the infrequent rains, and can turn into a big problem whenever it is disturbed, such as during renovation or further deterioration.  If air conditioning is used, it can generate mold problems when moist air (like from cooking or showering) hits cold air, or around the surfaces where cold condensate is produced.   

Low humidity also means little to no mosquitoes and many other biting insects.  Low pollution (when the wind is not kicking up dust) and warm weather can also be a positive for those who suffer from breathing problems like asthma.  

One problem of low humidity is its effects on the human body (see our article).  Dehydration can become evident in dry skin, hair and nails, respiratory system and through your whole body, affecting every major system.  In addition, static electricity builds up in your clothing and furniture, which can hurt and damage electronics.  Finally, dry air allows pathogens to stay afloat in the air for longer periods of time.  

Most deserts have very little cloud cover and thus a lot of sunshine.  This, for sure has its benefits and drawbacks; it can be the cure for Seasonal Affective Disorder (SAD) but also present higher risk for skin and eye damage and cancer.  Exposure to UV sunlight was associated with lower systolic blood pressure (the first number in a blood pressure reading) regardless of the temperature. (Could sunshine lower blood pressure? Study offers enlightenment)  In addition, sunlight assists your body in making vitamin D, which strengthens bones, and sunlight promotes collagen production in your connective tissue, which helps you move quickly. (7 Health Benefits of Living in the Desert)

The purifying power of sunlight should not be underestimated.  Those who live in or near the desert can use the UV rays of sunlight to purify water, their laundry, and anything else they can bring outside for a good “freshening”. 

One important disadvantage to desert life is dust.  In fact, you don’t have to live in the desert to suffer from the effect of desert dust, because dust from deserts can be transported on the wind and even injected into the troposphere, allowing it to travel great distances (such as across the Atlantic Ocean in the case of Saharan dust).  Dust clouds at surface levels bring particulate matter, coarse and fine, worsening air quality and posing respiratory or even cardiovascular risks.(What is desert dust and how does it change atmosphere and the air we breathe?)  The danger of dust presents in two different ways: size of the particles and content of the particles.  Particles that are approximately between 2.5 to 10 microns (PM10) are inhalable, but can be trapped and cleared from the upper respiratory tract.  Particles less than 2.5 microns (PM2.5) can lung alveoli, entering the blood stream where they cause systemic harm to other organs in the human body. (A Retrospective Cohort Study of Military Deployment and Postdeployment Medical Encounters for Respiratory Conditions)  Especially concerning is the class of particles less than 1.0microns (PM1.0), which are sure to enter directly into the bloodstream and may also cross the blood-brain barrier.  The toxic content of dust can be pathogens such as bacteria, including some that carry respiratory diseases (Characterization of Bacteria on Aerosols From Dust Events in Dakar, Senegal, West Africa), and most importantly, a fungus Coccidioides which causes Valley Fever.  It can also be bioreactive metals such as copper, chromium, nickel, lead and zinc, as well as pesticides, herbicides, radioactive particulates and aerosolized sewage (yuck!!). (Desert dust storms carry human-made toxic pollutants, and the health risk extends indoors)

Increased heat and low humidity also tends to decrease the number of negative ions in the air.  Elevated negative air ion levels are widely reported to have beneficial effects on humans including enhanced feeling of relaxation, and reduced tiredness, stress levels, irritability, depression, and tenseness. Depleted ion levels and enhanced positive ion levels are reported to have no effect, or deleterious effects. (Air Ion Effects

The study of how gasses in the earth’s atmosphere react with each other is very complex.  For example, it’s been shown that desert soil releases nitrogen species gasses into the air.  The release of NOx from desert soil and subsequent effective oxidation in the atmosphere indicates that the desert ecosystem is an important area for ozone production. This has been manifested by higher ozone in the desert air than the regional background from many observations (Güsten et al., 1996; Hoffer et al., 1982).  (Active Nitrogen Cycle Driven by Solar Radiation in Clean Desert Air)  Thus, higher levels of ozone in the desert could make it unhealthy for sensitive individuals.  These could become particularly high after rains, when microbes in the soil emit N2O (nitrous oxide, also known as laughing gas).  (Following rain, desert microbes exhale potent greenhouse gas)  In addition, it’s been shown that “stratospheric intrusions” (ozone-rich air descending from the stratosphere during spring storms) can also capture ozone created by pollution from Asia as they descend and transport it to desert areas of the southwest.  Particularly in the area of Las Vegas, these can create short episodes of high ozone that exceed federal air quality standards without factoring in local pollution.  (Background ozone burdens Las Vegas’ air quality in spring)

The other side of the coin is that in some areas of the world (like Atacama and Sechura deserts in Chile and Peru), dust from deserts can contain significant iodine, which actually destroys ozone.  (Iodine in Desert Dust Destroys Ozone)  Therefore, the mineral makeup of the soil in deserts is very important in characterizing what’s in the air. 

Living in/near the Forest

Forest bathing” is a Japanese term that emerged during the 1980’s as an antidote to tech burnout: it’s being calm and quiet amongst the trees, observing nature around you whilst breathing deeply can help both adults and children de-stress and boost health and wellbeing in a natural way. (How to start forest bathing)  If you regularly spend quiet time in the outdoors, perhaps you are already aware of its benefits: lower blood pressure, heart rate, and levels of harmful hormones like cortisol.  (Forest bathing: What it is and why you should try it)

What is in the air of forests?

Phytoncides are aromatic compounds from plants which can increase your number and activity of natural killer cells, a type of white blood cell that supports the immune system and is linked with a lower risk of cancer. These cells are also believed to be important in fighting infections and inflammation, a common marker of disease.  In one study, researchers found that people who took a long walk through a forest for two days in a row increased their natural killer cells by 50% and the activity of these cells by 56%. Those activity levels also remained 23% higher than usual for the month following those walks. (Why Spring Is the Perfect Time to Take Your Workout Outdoors)

Hinoki cypress, cedar, oak, pine and spruce are just some of the trees to release phytoncides (aromatic compounds), which include alpha-pinene and d-limonene.  Although these are actually VOCs, they are termed biogenic VOCs (BVOCs) because they are naturally made, unlike chemical VOCs that are manufactured.  Pinene and limonene are monoterpenes, which global annual emissions amount to 330–480 million tons. When visiting a forest, monoterpene VOCs such as limonene and pinene are mainly absorbed through inhalation, their blood levels rapidly rise after exposure, and they are mostly eliminated unchanged both in exhaled air and in the urine.  The tree composition can markedly influence the concentration of specific VOCs in the forest air.  Although essential oils do contain BVOCs, not all BVOCs are present in essential oils, and some molecules included in essential oils are not part of the BVOC molecular suite but are rather artifacts of distillation. (Forest Volatile Organic Compounds and Their Effects on Human Health: A State-of-the-Art Review)

Some other benefits of forest living are:

  • Humidity: in moderate amounts, humidity is good for the skin and respiratory system, 

  • Cooling effect: trees cool air through evapotranspiration. As trees transpire, they release water into the atmosphere through their leaves. As the water changes state from liquid to vapor, the surrounding air is cooled, similar to how we sweat.

  • Particulate matter capture: Forests can improve public health greatly by catching dust, ash, pollen and smoke on their leaves, keeping it out of our lungs.

  • Trees are sinks for other harmful pollutants, such as nitrogen oxides, ammonia and ozone, which can all cause respiratory problems from repeated exposure. (The Important Relationship between Forests and Air)

  • Healthy forest air includes bacteria, fungal spores, plant and animal particles and pollen, which may have good and bad effects.  Good effects of exposure to these include desensitization to allergies (exposure therapy), and certain bacteria, like Mycobacterium vaccae (a bacteria strain that lives in soil), which can stimulate serotonin production, and can make you feel relaxed and happier, as well as reduce inflammatory responses to stress. According to Dr. Christopher Lowry, “Surprisingly, when adults engage in soil-mixing activities for ten minutes with soil that is ‘spiked’ with M. vaccae ATCC 15483, there is a rapid alteration in brain activity within the occipital cortex and alteration in the plasma metabolome, relative to soil that is not spiked with M. vaccae ATCC 15483 [35]; this suggests that exposures to mycobacteria not only have long-term immunoregulatory effects but also alter physiology and neurophysiology within minutes. Perhaps we all really should spend more time playing in the dirt.” 

  • Ions: That “fresh air” feeling in the forest also comes from higher than normal presence of ions.  Negative air ions (NAIs) are an important indicator of air quality, and are significant for the evaluation of air conditions. In a 2020 study of a scenic area in China, negative air ions were present in forested areas  approximately 3.2-3.4 times over the numbers in open areas or the lake.  (For more information on the cleansing power of ions, read our post here!)

And the cons of forest living: 

  • Humidity: many forests are high in humidity, which can promote mold growth.  Without dehumidification in a home, it would be difficult to live in many forested areas because of mold growth. 

  • Radon: Trees are sources, sinks, and conduits for gas exchange between the atmosphere and soil, so radon, a product of uranium decay in the soil, is naturally expired by trees along with other gasses.  Although radon accumulation in homes through their foundation (the rocks and soil below the foundation) is most concerning, emission of radon by trees will cause a forest to have a higher level of radon than unforested areas, because radon is approximately 7.5 times heavier than air, so that living in or near the forest may increase the ambient level of radon outside the home depending on winds.  There are two units of measurement for radon, picocuries per liter, and becquerels per cubic meter.  According to a 2015 study in Brazil, radon concentrations as high as 40 kBq/m3 (40,000 Bq/m3) were found in a national forest.  The EPA recommends that homeowners take action to lower radon levels in their homes if there is a level above 2 pCi/L.  Since one pCi/L is equivalent to 37 Bq/m3, the measurement in the Brazilian forest showed 1,081 pCi/L, or 250 times the upper limit of radon recommended by the EPA!  Thus, the study rightly inferred that “the results indicated considerable radon hazard for human occupation in the neighborhood.”

Overall, the desert and the forest are two vastly different climates, yet each have potential for healthy lifestyles for those who can live further away from urban areas.   From forest bathing to hiking to biking, there are plenty of ways that each environment offers us to connect with nature and take in its natural health benefits. 

More Enzymatic Cleaners to the Rescue!

More Enzymatic Cleaners to the Rescue!

If you read our article “Breaking down Mycotoxins and mVOCs with Enzymes and Non-Toxic Cleaners”, we described that certain enzymes can be used to break down mycotoxins, the toxic products of mold, which can otherwise be very hard to eliminate.  Enzymatic cleaners specifically targeting mold and mycotoxins are few, but we wanted to let you know that all-purpose enzymatic cleaners work on stains, odors, and general cleaning duties all around the house!

First of all: What is an enzyme?   Enzymes are proteins produced by living organisms that act as catalysts in chemical reactions.  Enzymes can either build up or break down.  For our purposes, cleaning enzymes facilitate breaking down microbes and their byproducts that cause sickness, stinkiness or stains.  

Scientists have been exploring making artificial enzymes since the 1990’s, and many of these are mimicking enzymes found in nature.  Here are the most common types of natural enzymes (from Simple Science: How in the World do Enzymes Clean?):

  • Proteases break down protein-based soils including blood, urine, food, feces, wine and other beverages.

  • Lipases break down fat molecules like oils and grease.

  • Amylases break down starch molecules like eggs, sugars, sauces, ice cream, gravy.

  • Cellulases are used to soften fabric and restore color to fibers made up of cellulose material. They also remove particulate soil and reduce fabric graying and pilling.

Enzymes were initially produced by extraction from glands of various animals; however, modern enzyme production is done through fermentation of various fungi and bacteria through the steps of fermentation, recovery, and standardization.   (about Cleaning Products: Enzyme Science

Enzymes and purely enzymatic cleaners are not “alive”.  Bio-enzymatic cleaners, however, do combine enzymes with bacteria, which are “alive”. Examples are drain cleaners and some pet stain removers.  

Enzymatic cleaners are marketed to pet owners (and even more so to cat owners) because cat urine can be especially concentrated (cats make the most of the little water they drink), and so once it’s deposited, the ammonia and hormones in the urine start to smell, and bacteria start breaking it down into urea.  It’s an unmistakable fragrance, and enzymatic cleaners are regularly recommended by veterinarian and pet experts for pet accident cleanup (the ASPCA, mobile vet company The Vets, and professional veterinary site DVM360 are just a few examples).  

Some of the benefits of enzymatic cleaners are:

  • They tend to be more powerful by working on more substrates (surfaces, conditions) in lower concentration than chemical cleaners.  Therefore you use less, resulting in less packaging.

  • They work at moderate pH and temperature, allowing for milder detergents and less energy, like cold-water laundry detergents.

  • Enzymes are not mutagenic (causing changes in DNA) and not clastogenic (causing breaks in chromosomes).  They are not reproductive or developmental toxins and have a low toxicity to aquatic systems.

Some of the cons of enzymatic cleaners are:

  • They can have storage time limitations before the enzymes become less active.

  • They can have storage temperature limitations.

  • They can take longer to work.

  • Some enzymatic cleaners (especially carpet cleaners as in this video) can leave an oily sticky residue if the cleaner is not washed away, which can attract soil/stain even more.

  • They can have inhalation dangers if the cleaner is in powder form, but many formulations are now in dust-free granules that avoid this danger.

  • They can be incompatible with other cleaners like bleach and chemical disinfectants, which can deactivate the enzymes.

So, here are some enzyme cleaners you might like to try:

For pet owners:  Rocco & Roxie Stain & Odor Eliminator for Strong Odor - Enzyme Pet Odor Eliminator for Home has a LOT of fans for the way it quickly and thoroughly eliminates pet odors and stains (just read some of the comments/watch videos).  Although their ingredients are a bit mysterious (Water, advanced biological blend, non-ionic surfactant, odor counteractant), the company says it is safe to use around pets and children, and certified safe for all carpets from the Carpet and Rug Institute (CRI).  They also offer a 100% money-back guarantee if you’re not satisfied.

For anyone who cleans: TweetMint Enzyme Cleaner contains no volatile organic compounds (VOC) or synthetic chemicals. It's completely free of artificial colors & fragrances, preservatives, animal products or by-products and has not been tested on animals.  Since it’s concentrated, a little (just ½ oz) will make ½ gallon of medium-strength concentrate, and the website publishes a whole list of jobs like cleaning windows and floors, degreasing, stain removal, odor elimination, and even pest control (garden and home).  The active ingredients are purified water, anionic/nonionic surfactant blend, glycerin, enzymes, peppermint oil, sodium borate. Sodium borate is a naturally-occurring compound made of boron, oxygen, hydrogen, and sodium, and in 2020 the Cosmetic Ingredient Review (CIR) Expert Panel evaluated data and concluded that sodium borate is safe as a cosmetic ingredients in concentrations less than or equal to 5%.. (Sodium Borate: Is it Safe?)

For anyone who showers or washes clothes:  Zerotaboos (ok, just put a space in there to easily say it: zero taboos!) is a woman-owned company which uses prebiotics (simple sugars, which are food for beneficial bacteria) and postbiotics (Lactobacilli ferment filtrate) in their products to encourage growth of good bacteria so that you don’t need harsh chemicals and fragrances to smell better.  Their Laundry Enzymes contain 10% nuclease enzymes, the strongest concentration available and the best for breaking down body odor.  It doesn’t replace your regular laundry detergent, but does a good job of removing troublesome body odor from clothing so that it actually smells fresh again after washing!  This owner knows her stuff and cares about her customers (see video on why she stopped offering refill packaging). For sure, bacteria and their byproducts have fed odors and fears long enough…it’s time to turn the tables by putting good bacteria and enzymes to work for us!

Photo by Daiga Ellaby on Unsplash

Flood and Leak Preparation/Remediation Guide

Flood and Leak Preparation/ Remediation Guide

Water damage (including damage from freezing) is one of the most common and most costly types of homeowners insurance claims. Every year, about one in 50 homeowners files a water damage or freezing claim, accounting for 29% of all homeowners insurance claims, according to the Insurance Information Institute. (forbes.com) With the right knowledge and preparation, we hope that you can avoid very costly damage even if you experience a flood event.  That’s the purpose of this guide and kit. 

Before: secure lawn furniture, vehicles, and windows and doors

Flash Floods can happen with no notice, but if you have time, try to do as much of the following as possible to keep water and wind out.

  • Park your vehicle in a garage above street level if possible  

  • If high winds are forecasted, install hurricane shutters or plywood over windows and glass doors if possible. Store lawn furniture and bikes in a garage and roll or move heavy decor like pots to sheltered places.

Before the storm/flood: Take photos of your property inside and out for documentation (which hopefully will not be needed!).  Move valuables like photos and jewelry to a high, safe place in the home.

Before: prepare a basic survival kit for weathering the storm at home, as many times floods cause power outages.  

  • Drinking water (one gallon per person per day for several days, for drinking and sanitation)

  • Food (at least a several-day supply of non-perishable food) 

  • Manual can opener (for food)

  • Battery-powered or hand crank radio and a NOAA Weather Radio with tone alert

  • Flashlight

  • First aid kit

  • Extra batteries

  • Whistle (to signal for help)

  • Dust masks (N-95 if possible) (to help filter contaminated air)

  • Plastic sheeting and duct tape to protect furniture from water

  • Hand sanitizer

  • Moist towelettes, garbage bags and plastic ties (for personal sanitation)

  • Wrench or pliers (to turn off utilities)

  • Local maps

  • Cell phone with chargers and a backup battery

  • Various buckets for leaks

Minimum Tools for Clean-Up:

  • Utility knife with extra blades for cutting drywall

  • Pry bar and hammer

  • Heavy duty gloves

  • Heavier plastic tarp(s) for temporary repairs and drywall disposal

  • Heavy duty “contractor” bags for disposing of wet drywall, carpeting and water-damaged items

  • Flat shovel for removing debris from floor

  • Wet-dry HEPA vacuum

During the storm/flood: 

  • Don’t open windows or doors during the storm, as flying debris can cause serious injury!  Contrary to urban legends, you shouldn’t open them to “equalize pressure” during a tornado situation, either.  

  • Keep your weather radio tuned and cell phone on for local updates and take shelter in an interior room or the basement if advised against tornadoes. 

  • Occasionally tour the house and peek at attic space (if you have one) to check for leaks. Use buckets to contain water and if a steady drip of water starts to come from one area, use a utility knife to cut through the ceiling drywall to let the water run out faster and avoid blowout of the ceiling.  

  • Don’t stand in or walk through water to avoid risk of electrocution


  • Venture outside only when it’s safe to do so (the storm has passed). 

  • Alert authorities if your power is out or there are downed power lines near your property

  • Don’t drink tap water unless it’s deemed safe to do so

  • Take “after” photos inside and out

  • Be aware of displaced wildlife like snakes, alligators and the like!

  • Make repairs as you are safely able to do so.

  • If you have to leave your home for safety, write the date, your name(s), destination and phone number on a prominent wall as information for rescue teams

The Clean-Up:

When flooded by a hurricane or flash flood, the waters invading your home contain a variety of pathogens such as E. coli, Salmonella, and Shigella; Hepatitis A Virus, agents of typhoid, paratyphoid and tetanus, as well as agricultural or industrial chemicals (OSHA.gov).  This means that contents and surfaces that came in contact with floodwater from outside must be sanitized and completely dried within 48 hours or disposed of; do not let them just “dry out”.  Then after cleaning and drying, mold prevention treatment can be applied. 

Tips for salvaging household items (adapted from haywardscore.com):

Papers and clothing 

  • Move outside and spread out in sun

  • May wash clothing in washer

  • Papers and clothing soaked in contaminated water should be disposed (clothing will contaminate washing machine)

Solid wood furniture

  • Move outside to dry thoroughly

  • Remove drawers

  • Tip back to expose underside

  • Wipe down with clean rags

Area rugs

  • Can be professionally cleaned with extraction method

  • Washing them in your machine may contaminate the machine

  • Rugs with foam backings should be disposed

Wall-to-wall carpeting

  • Since it must be cleaned and thoroughly dried within 48 hours, and this is hard to do in the case of large areas of carpet, disposal is most common.

Padding under wall-to-wall carpet

  • Dispose because it is difficult to completely dry.

Upholstered furniture like couches and recliners

  • Must be cleaned and thoroughly dried within 48 hours.  

  • Move them outside if the weather is dry

  • Tip back so that the underside is exposed

  • Remove cushions and covers if possible to dry faster. 

  • Use a wet-dry shop vac to remove as much water as possible, then use fans to circulate air over them continually.

  • Thoroughly soaked furniture is unlikely to be completely cleaned and dried: disposal is recommended.

Drywall:  If any water pooled on the floor near walls, then it likely contacted the bottom of the drywall and insulation and needs immediate attention to get the walls dry.  The following is adapted from PopularMechanics.com:

  1. Wearing a respirator mask, safety glasses and gloves, remove baseboard with a prybar or hammer claw.

  2. Place a tarp under the area you will start to cut to catch drywall debris.

  3. Mark walls 6-12” above the high water line (use a chalkline or laser if possible) and cut using a utility knife, drywall saw or light circular saw set at ½” depth.

  4. Punch out the drywall under the cut with a hammer and remove it from the studs.

  5. Cut away insulation using a utility knife, making sure that you remove all damp insulation.

  6. Haul out debris on the tarp and repeat until all affected walls are open.  

  7. Use a wet-dry HEPA vacuum throughout the process to keep dust down

  8. Remove electrical plates to promote drying within the wall.

  9. Disinfect floors and cavities with a degreaser/cleaner and pressure washing to clean out all the bacteria from floodwater (not necessary if it was clean water) (moldfreeliving.com)

  10. Use drying equipment (see below) to expedite drying.

If entire ceiling areas and walls are soaked (from roof damage), remove all items you wish to salvage in the room before tearing out drywall and insulation (best done by professionals).  Unfortunately, all wood, tile, and vinyl flooring must be removed eventually because incomplete drying in-between and under the floor will cause mold to grow (also best left to professionals).  

How to use Drying Equipment: Drying out a house is actually an art.  Remediation companies use their equipment to get the right humidity, airflow, and temperature (HAT), the elements necessary for evaporation, during different stages of drying. The following advice is from the article Expediting the Drying Cycle:

  • Low relative humidity (RH) is necessary for drying, as moisture in materials and air seek equilibrium. The lower the RH of the air, the quicker the wet materials will give up their moisture to become equal with the moisture in the air.  Use any dehumidifier available from the first day, in order to get the RH as low as possible and keep it there.  It’s important to use the wet-dry HEPA vacuum as much as possible before switching on fans, as dust can plug filters on the dehumidifiers and reduce their drying capabilities. 

  • Airflow measured in feet per minute (FPM) is more important than cubic feet per minute (CFM).  Airflow speed at the beginning must be aggressive, preferably 600 FPM or more.   This is why professional blowers sit low on the floor to move air directly across flooring surfaces.  Alternate the blower between rooms if you only have one blower. 

  • Heat is needed when rates of evaporation begin to slow down, usually on the second day of drying.  At this time, if you have a room heater, turn it on and slow down fan speeds to 150 FPM.

  • Consistently low RH is the most important goal, because RH drives drying. Toward the end of the drying job, it’s possible that only one airmover is needed in each room (where the drying goal has not been met) with all available dehumidifiers running.

Wait until everything completely dries in the walls (consistently low RH can indicate this) before applying any anti-mold products.  Here are some recommended mold preventatives:

  • For a large area, consider having it soda blasted by professionals to remove remaining debris and mold from the structure in hard-to-reach places. 

  • DIY Fogging to prevent mold growth:  EC3 Mold Solution Concentrate and Fogger, $495

  • Laundry: EC3 Laundry Additive, $23

  • Use the Mold Guard and Air Angels after drying to continue elimination of mold in all areas.

  • Use TotalClean to wipe down surfaces like countertops, windows, cabinets, mirrors

Consider using an Ozone Generator to kill mold and remove odors:

  • Ozone generators should only be used once all surfaces that can be cleaned are thoroughly cleaned (walls, floors and ceilings too!).  

  • Ozone is not as effective in areas of high humidity, so running the air conditioner or a dehumidifier in the space to get the humidity down (60% or less) is advisable.  Central air conditioning and any exhaust fans must be shut down when using the ozone generator, though, because you’ll want the ozone to stay in the space. 

  • Use fan(s) within the space to circulate the ozone.

  • Ozone generators cannot be used in the presence of people, pets or plants, but once these are removed, they can be quite effective in removing smoke.  Follow all instructions to seal up the space and allow it to work for the full time advised before ventilating.  Contact HypoAir regarding rental, or local restoration companies may rent ozone generators.  

A Sticky, Fragrant Solution to an Old Problem

A Sticky, Fragrant Solution to an Old Problem

While reading a new scholarly article on creating water filters from ceramic pots with nanoparticles of silver in them, I thought, I’ve read about this before; it’s not new.  This type of system has been used in Africa and other disadvantaged areas that lack access to clean drinking water.  In fact, the authors disclosed that “Using silver particles for water filtration is not the main innovation. Others have used this technology in the past. The key is controlling the release of nanoparticles, which can reduce the usable life of the filters.”

This filter has roots in proved science: that silver is antibacterial.  Silver has positively charged ions that fight bacteria in three ways (check out our article to understand them).  Silver nanoparticles can also penetrate through the bacterial biofilms (the slime that bacteria make to live on surfaces) to completely destroy them and can even prevent microbes from developing biofilms.  (This is a great attribute for water pitchers, where standing water can allow biofilms to develop.)

So, the new part about this water pitcher/filter is what the silver nanoparticles are suspended in: pine resin.  Apparently, pine resin is an old source of a “newer” category: polymers.  Polymers have gained a lot of attention in the last few years because they have a lot of desirable properties such as versatility and durability.  By definition, polymers are large molecules made by bonding (chemically linking) a series of building blocks. The word polymer comes from the Greek words for “many parts.” Each of those parts is scientists call a monomer  (which in Greek means “one part”). (Explainer: What are polymers?)  DNA and keratin (the material our hair and nails are made of) are natural polymers. 

Pine resin is the hardened form of the sticky sap that runs out of pine trees when they are cut, but inside the tree it carries water, nutrients, sugar and mineral elements throughout tree trunks—similar to how blood functions in the human body. (5 Uses for Pine Sap: How to Harvest and Utilize Pine Resin

Although it’s possible to get resin from the tree by cutting into it to harvest sap, this kind of damage can kill the tree.  Otherwise, you can collect resin crystals that have formed on the outside of the tree from natural damage, heat them, and use the liquid resin for many means, such as firestarters (pine resin is high in turpenoids, the VOCs that make it smell like a pine tree), herbal remedies and soap, and natural glue.

This semi-solid, sticky nature of pine resin is also what makes it great for coating the inside of a water pitcher filter.  Without it, the silver nanoparticles could react quickly to chemical impurities, which would make them unavailable for killing bacteria.  The following diagram shows how silver nanoparticles embedded in the pine resin can be released more slowly to allow the pitcher to last longer as a filter.

(And, in fact, the other new part about this outreach was that the community in need of these filters is in the United States.  According to this article from March 2023, the Navajo Nation reservation stretches across 27,000 square miles in Arizona, Utah and New Mexico. Fifteen to thirty percent of the 170,000 people who live there do not have access to clean, reliable drinking water.  Although estimates vary according to the EPA vs. the tribe, it’s the “why” this continues…according to an EPA article, in 2003 the Navajo Nation estimated that up to 30% of the population did not have piped water to their homes.  The EPA and HUD have worked to reduce this number, which they estimate has helped lower the percentage of the population without access to piped water to their homes to about 15%.  Twenty years later, many must drive miles to haul water home or use unregulated water sources, which are susceptible to bacterial contamination and/or exceed drinking water standards for uranium and other chemicals, because some homes are located near abandoned uranium mines.)

Source: Pottery Becomes Water Treatment Device for Navajo Nation 

Since the pottery and the resin are very natural elements that the Navajo respect and use, this type of filter could be very important to many in easing their burden of getting clean drinking water, and even after every home receives piped water (but given the history of this project, the “when” is not in sight).  At HypoAir, we like natural elements too, so learning about the properties of a material that has been all around us for centuries is very exciting!  

Photo by Jeremy Bishop on Unsplash

The Consequences of Flushing the Toilet with the Lid Open

The Consequences of Flushing the Toilet with the Lid Open

Spoiler alert: the consequences are not pretty.  This calming (Australian?) voice and wonderful orchestral soundtrack in this December 2022 video belie the serious and gross subject: how much germs and fecal matter shoot out of a toilet when you flush it.  The University of Colorado Boulder researchers who produced the video found that airborne particles ejected from the toilet traveled at speeds of up to 6.6 feet per second (that’s a very fast walk at 4.5 miles per hour) and reached 4.9 feet above the toilet and smaller particles measuring less than 5 microns hung in the air for more than a minute. 

It’s not a new subject (the subject was first revealed in a 1975 study, and another 2013 study warned about the toilet plume) but the video using UV light brings it to the forefront of our minds and hopefully, engages us in healthier bathroom habits such as closing the lid and sanitizing surfaces more frequently in our own private bathrooms. 

So what should we do?

Ever since Febreeze informed us that odor can be caused by bacteria, bathroom odors are particularly noxious, as we know that the substances that cause it definitely have dangerous bacteria.   There are different ways of removing/preventing bathroom odor (and thus bacteria).  In light of the knowledge of toilet plumes, toilet sprays like PooPourri, although emitting a pleasant odor, seem to be one of the least effective because while spraying on the bowl creates a scented vapor, it does not prevent the emission of bacteria and particulates into the atmosphere.  Other products on the market that have been invented to remove toilet odors at the source, using hardware to pull vapors from the bowl area.  These include:

  • Potty Sniffer Toilet Odor Ventilation System ($271 and up): fan directs air from bowl into a nearby vent.  This is the preferred place to direct these gasses.  However, installation is a bit more complicated as connecting to a vent may require to drill into drywall or cabinets, which needs work to conceal. 
  • JonEvac  Toilet Seat Ventilation System ($300): Replaces your toilet seat with a special seat that has ventilation channels on the underside.  Fan needs to be plugged into a regular wall outlet and activated carbon filter ($80) needs to be replaced every 1-2 years.
  • Splashblocker was invented primarily for hospital settings.  It is a portable “shield” to protect healthcare workers from disease and hazardous drugs (like chemotherapy) that are excreted in patients’ waste, which are aerosolized whenever the toilet is flushed. Previous to this invention, caregivers often placed plastic-backed absorbent pads (such as are used in keeping beds dry from incontinence) over the toilet before flushing, but the cost of these adds up and can easily be sucked down the toilet, creating big plumbing issues.
  • According to this 2020 study, a redesigned toilet seat that can spray a “liquid curtain” of water or sanitizing solution over the bowl when you flush can effectively impede upward movement of particulates, and only 1% of (bacteria/virus-laden) aerosols enter the air above the toilet seat.

The forceful flushing of vacuum-assisted flush toilets, which are commonly used in public restrooms (and all airplanes), actually do a great job of eliminating the toilet plume.  This video uses blacklight just like the study at the beginning of the article, and the difference between regular toilets and this vacuum system seem to be huge.  There were no particles coming out of the vacuum-assisted toilet, but many coming out of the regular flush toilet.  Vacuum-assist toilets still use water to help flush, but nowhere near the amount of regular gravity systems.   This fact comes from the AcornVac website (a manufacturer/supplier of vacuum toilet systems): “a 500 person commercial office building that is serviced by a single vacuum center and 1/2 gallon per flush vacuum toilets will save over 265,000 gallons per year, compared to conventional low flush toilets.”  Water savings aside, I think that the absence of a toilet plume when using a vacuum toilet is their greatest benefit, and it makes me feel a whole lot better about using the bathroom on airplanes!

What happens when the lid is lowered?

Since vacuum-assist toilets and shields are not commonly installed in residences, most people have only a lid to guard against the toilet plume.  What happens when you put the lid down and flush?  Obviously, there are particulates and germs landing on the inside of the lid.  (This is an area that gets skipped over when cleaning, I’m sure!)  The rest of the particulates exit through the spaces between the toilet, seat and lid.  Here are the good and bad results of flushing with the lid down, assessed by researchers at University College Cork:

  • Reduced the number of both visible and smaller droplets during and after flushing by 30-60%
  • increased the diameter and concentration of the bacteria in these droplets.
  • airborne microdroplets were detected for 16 minutes after flushing the toilet with the lid down, 11 minutes longer than when the toilet was flushed with the lid up. 
  • Another study concluded that lowering the lid before flushing “reduced 48% of total number concentration, 76% of total surface area concentration, and 66% of total mass concentration, respectively.”

Using the lid when flushing definitely helps, however some aerosols are still shooting out, and hanging around even longer.  What are the other things we can do to protect from THE PLUME?

  1. If you are in a public place and concerned about transmission of disease, put on an appropriate mask before going into the restroom–at least the aerosols should be filtered out of your air, and germs will not land on your nose or mouth.  As always, wash your hands thoroughly, and don’t touch your mask or face!
  2. If you’re at home, it goes without saying to clean regularly.  
    1. Use a non-toxic disinfectant on all surfaces in the bathroom.  Check out our article on the differences and methods of cleaning, sanitizing and disinfecting. 
    2. Change hand towels frequently, at least twice per week.  For towels and clothing that have been exposed to toilet plume, you can add Borax to your laundry, or pre-soak with it, as it turns into hydrogen peroxide when hot water is added to it.  It’s also generally safe for colored clothes.
    3. Use a HypoAir bipolar ionizer like Germ Defender or Upgraded Air Angel Mobile to sanitize the air and surfaces in your bathroom 24/7!
    4. Leaving your toothbrush in an open place on the bathroom counter sounds icky (for obvious reasons), but stashing it away in a plastic container or drawer is not advised either.  According to a meta-study published in 2012,  toothbrushes stored in aerated conditions had a lower number of bacteria than those stored in plastic and bacterial growth on the toothbrush increased 70% in a moist, covered environment.  What should we do with our toothbrushes?  Sanitize your toothbrush regularly by soaking it in hydrogen peroxide, Listerine, or using an approved UV sanitization device (but not in the microwave). (Is your toothbrush covered in poop? Here's how to thoroughly clean it)
    5. It’s best to switch on your bathroom exhaust fan before every flush, and leave it running for at least 15-20 minutes afterwards.  If your exhaust fan does not seem to remove odor very quickly, then you know it’s not removing the “toilet plume” aerosols.  It may be under-sized, or just old and inefficient.  Because the bathroom exhaust fan is also a very important appliance to remove humidity (and thus prevent mold), check out our article on how to check its size and where it should be vented!

Sorry, I know after seeing that first video, I couldn’t “un-see” it, but I’m grateful that non-toxic cleaners and laundry methods have been invented.  We just need to somehow lower the cost of vacuum-assisted toilets, and bathrooms will get a lot cleaner!  

Can my indoor air quality affect the food I eat?

Can my indoor air quality affect the food I eat?

Do you ever look at the food on your countertop, whether it’s an apple pie or bowl of potatoes, and wonder, how did that food go bad so fast?  It’s a common problem, even more so in warmer climates, so we thought you’d like to know how your indoor air quality affects your food!

Admittedly, not all spoilage comes from your own air.  It’s been recognized that food processing plants need to have better air contamination control during the food production process.  “Primary  air  pollutants  in  the food  industry  are marked,  being,  in addition  to  microorganisms, suspended particles, combustion  products (nitrogen oxide,  carbon monoxide, carbon dioxide,  sulfur oxide) and volatile organic substances.” (2019 Meat Industry Conference Paper)  The contamination of food products is dependent on:

  • air’s microbial load, and 

  • on the duration of exposure to the air, whether during specific technological processing stages (e.g. cooling) or during storage (from book: Hygienic Design of Food Factories, chapter 14: Managing Airflow and Air Filtration to Improve hygiene in food factories).  

Air in slaughterhouses and sausage production facilities, for example, is more than 10 times more laden with yeasts and molds than dairy processing facilities, because of contamination that can come in on the product (animal feces).  The second point is that the product contact with air needs to be limited in order to limit its contamination.  Air  quality  is  particularly  important  in facilities for  production and packaging of butter, if this is manufactured in open-type mixers, since these devices can also incorporate up to 5% of the surrounding air into the product [Varnam  A  and Sutherland  J  P  1996 Milk  and  Milk  Products: Technology,  Chemistry  and Microbiology 1st ed, Chapman and Hall, London, p 451].

Another factor that causes spoilage during food processing is humidity.  There are three ways that humidity affects the food: 

  • Condensation on equipment and food can accelerate microorganism growth

  • Dry foods can absorb moisture that will lead to microorganism growth

  • Packaging like paper and metal start to degrade, leading to spoilage

These insights into how food gets contaminated in factories are good for application in the home because although we can’t much control how it gets packaged, we can certainly control how it’s stored and prepared at home.  So let’s dive in…

The three main biological pollutants that cause food spoilage are bacteria, yeasts and molds. (online course)  Bacteria, yeasts and molds, which are typically small in size, can hitch a ride on larger particles like water droplets or dust.  Where do these come from?

The bathroom.  It’s not pleasant to think about, but “Germs will more likely spread after you flush, when bits of fecal matter blast into the air in aerosol form, a phenomenon known as "toilet plume." From there, Kelly Reynolds (a public health researcher at the University of Arizona) said, the "bits of fecal matter settle on surfaces, contaminate hands and then get spread to the eyes, nose or mouth." (USAToday.com)  Here are some ways to limit the spread of germs from the bathroom to the kitchen: 

  • Close the toilet lid before you flush.

  • Wash and dry hands before leaving the bathroom

  • Use an ionizer like the Germ Defender in the bathroom, to kill germs in the air and on surfaces.

Pets.  Similar to the slaughterhouse scenario, many of us have furry animals (pets) walking around in our food-processing facilities (kitchens).  Where these pets have been and what they have on their fur and feet can be really disgusting!  Worse, homes with litterboxes in the kitchen, or allowing pets to walk on the counters, is like placing a toilet in the kitchen or even on the countertop!  It’s just not pleasant to think about.  If you have pets and you have a kitchen, think about these reforms:

  • Bathing pets regularly so that bacteria and mold are minimized

  • Not allowing pets to walk on countertops

  • Keeping litterboxes in another area of the home away from the kitchen if possible

  • Spraying pets’ fur regularly with a safe anti-microbial spray like Remedy Mold Treatment Spray by CitriSafe.

  • Always wash your hands after touching your pets and especially before food preparation!

The refrigerator.  What?  How can the refrigerator work against us when we’re talking about food spoilage?  Actually, I’m not talking about inside the refrigerator, although that can be a problem (more on that later).  Here, let’s talk about what happens in the “guts” of the refrigerator, where the heat is actually released through the coils.  The speaker is Jeff May, a renowned air quality inspector.  

“I was sitting in my kitchen, and every once in a while, I’d start to wheeze, but just couldn’t understand why. One day, I realized every time the refrigerator turned on, I would have trouble breathing. Our refrigerator was only three years old, but in those days, the drip pan was accessible from the front. When I removed the grille and took it out, there was a pearl onion that somehow bounced into it. The onion had an inch and a half of Penicillium mold growing on it. So, every time the compressor turned on, it would blow mold spores out into the room. Every frost-free refrigerator has a heating cycle. The cooling coil gets full of ice, and you have to melt that ice in order for the refrigerator to cool. The water from that melt goes into a pan at the bottom. The heat from the compressor is supposed to evaporate the water, but very often, the water persists. There’s just not enough heat. So, if there’s any dust in that pan, mold growth ensues. And if you’re allergic to cats and dogs, and somebody had a pet in the house before you moved in, that refrigerator can be a perpetual source of allergens just from the dust that accumulated on the coils when the pets were there. We’ve had people who have just simply cleaned their refrigerator, and all of their allergies went away.” (Jeff May, during interview with author of moldfreeliving.com)

Now for the inside of the refrigerator: Ok, it seems like a no-brainer that you shouldn’t leave spilled food lying around in the fridge because it can contaminate other food by direct contact.  But using your fridge properly also prevents spoilage:

  • The real reason there is a Fruits and Veggies Drawer: it controls humidity in the drawer and prevents certain foods from ripening too fast.  If there is a vent or slot on the drawer, this is used to adjust the humidity and air flow (because ripening fruits also produce a gas called ethylene, which will cause other fruits exposed to it to ripen).  Closed vent or no vent = high humidity, and Open Vent = low humidity.  For a quick way to remember what to put in the “Crisper Drawers”, remember this rule of thumb: “rot-low, wilt-high.” Fruits that are prone to rot belong in the low-humidity drawer, while produce that's prone to wilting needs to be enclosed completely in the high-humidity drawer. (for a full explanation see article at epicurious.com)

  • Don’t put meat, cheese, milk and eggs in the door shelves!   The door of the refrigerator tends to stay at a higher temperature and these items will spoil more quickly (with nasty consequences) when stored there.  For more on where to store what food, this article helps a lot).

The FoodKeeper App from the FDA is a useful tool to determine how long to keep, and when to throw out specific foods.  It is also helpful to know why you need to preserve foods by refrigerating or freezing them right away (within  2 hours of cooking).  Bacteria are not killed by these colder temps, but their growth is slowed down or stopped.  Some bacteria and their endotoxins (toxins released by the bacteria through its life cycle and during death) are highly resistant to heat, so thoroughly re-heating them before eating does not kill the toxin! (check out our post on endo-and exotoxins here).  Staphylococcus aureus is one example of such a bacteria, and it can cause some serious food poisoning, even death.  

The dishwasher. Wait–the dishwasher is supposed to clean my dirty dishes, how can it be polluting my kitchen air?  If you have ever cleaned the vent on your dishwasher, you will know how absolutely filthy this spot can be.  Food residue, along with moist, steamy air will cause a thick slime to grow.  The rest of the dishwasher needs a deep clean too (not just using a bowl of vinegar and/or baking soda), but the vent especially is the area where escaping steam will carry bacteria into your kitchen air. 

Finally, keeping proper humidity in your home is super-important not only for your sinuses, but for food preservation too.  Some fruits and veggies should only be stored on the counter (check them out here), so the proper humidity will help them to stay fresh longer.  

Now you know how good air quality in your home means better food (especially in your kitchen).  By reducing the bacteria-load in the air, reducing exposure to the air, and keeping proper humidity in the air, you can waste your precious foods less, and enjoy them more!

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

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 Christian 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):



Are released during death, mechanical damage and lysis of bacteria but also during bacterial growth and division. (bmglabtech.com)

Secreted as part of the cell’s metabolism

Does not have any enzymatic activities

Most activities are enzymatic in nature

Immune response is weaker

Immune response is stronger

Made of lipopolysaccharides

Made of proteins

Moderately toxic

Highly toxic

Cannot be made into toxoids

Can be made into toxoids

Highly resistant to heat

Can be killed by boiling

(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 (Endotoxins: Small But Very Significant):

  • 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)

Here are some more details about endotoxins.  Although it’s a little in-depth, this article gives a good explanation of what endotoxins are and how they are released (shed) from bacteria.  Basically, endotoxins are small molecules of lipopolysacchride (LPS), which comprise approximately 70% of the outer membranes of gram-negative bacteria. They are responsible for maintaining structural integrity and have been shown to be essential for bacterial survival.  Lipopolysacccharides vary in their structure, but all share three distinct regions:

  • O antigen repeats are found on the outermost domain of the LPS molecule and are responsible for host immunogenicity (the ability of the endotoxin to provoke an immune response in human cells).

  • Core domain is composed of sugars and other non-carbohydrates.

  • Lipid A is the lipid component of LPS, whose hydrophobicity (repels water) facilitates membrane anchoring. Lipid A is responsible for toxicity of the endotoxin.

Here is a diagram of this structure:

Source: What are endotoxins?

Endotoxins are naturally shed at low levels during bacterial growth, but are released in much larger quantities upon cell death when their cell membranes rupture and disintegrate.  A single E. coli cell can release up to 2 million LPS molecules!  As lipids, endotoxins are naturally hydrophobic, which gives them a strong affinity for plastics and hydrocarbon-based materials (vinyl flooring, polyurethanes and coatings on many new products).  

The Limulus Amebocyte Lysate (LAL) test detects endotoxins.  It comprises blood cells (amebocytes) from the Atlantic horseshoe crab (Limulus polyphemus) that clot when they encounter bacterial endotoxin lipopolysaccharides.  The LAL may be used to test in three different ways: to provide a yes/no (qualitative) answer to whether a sample contains a specified amount of endotoxin, or to obtain the quantity of endotoxin via how fast the clotting takes place (turbidimetric) or how intensely the color changes (chromogenic). (Bacterial Endotoxins Testing)  In the qualitative test, equal amounts of a test sample and the gel clot LAL are mixed in a test tube and incubated at 37 °C for 60 minutes.  After the incubation, the tube is inverted.  If sufficient endotoxin is present in the test sample, the solution would have clotted during the hour incubation and a gel will remain in the bottom of the inverted tube (see image below).  If the sample does not contain detectable endotoxin, no clot will form and liquid will run down the side of the inverted tube.  (LAL/TAL Endotoxin Detection Test Methods)  The enzymatic reaction between the endotoxin and lysate produces a yellow color, the intensity of which is directly linked to the quantity of endotoxin present in the sample.   

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!

Photo by CDC on Unsplash