• Percentage of households in the U.S. and Canada affected with mold, according to a Harvard study: 50%.
• Amount of increase in respiratory problems for people living in homes where mold is present, according to the same Harvard study: 50 to 100%.
• Number of patients in the U.S. with chronic respiratory problems, according to the Mayo Clinic: 37 million.
• Percentage of cases of chronic sinusitis caused by mold allergy, according to a study by the Mayo Clinic: 93%.
• Number of mycotoxin molecules that could be carried by a single housefly: 7.35 billion.
• Number of people who could be killed by the amount of mycotoxin that could be carried by one housefly: 100,000

Toxic Mold in History

Toxic mold probably has been with mankind since the beginning of time.

Ergotism

A species of mold called ergot, which grows on wheat and rye, has been known for centuries to cause a disease called ergotism. People who eat ergot-infested grains develop circulation problems that can lead to gangrene and even death.

Biblical Mildew

In the book of Leviticus, Chapter 14, verses 33-57, priests are urged to inspect a house after a flood:

“If the mildew has spread on the walls, he is to order that the contaminated stones be torn out and thrown into an unclean place outside the town. He must have all the inside walls of the house scraped and the material that is scraped off dumped into an unclean place … After the stones have been torn out and the house is scraped and plastered, the priest is to go examine it, and if the mildew has spread in the house, it is destructive mildew: the house it unclean. It must be torn down … Anyone who sleeps or eats in the house must wash his clothes.”

King Tut’s ‘Curse’

Many treasure hunters and laborers became ill, and some died, after the discovery of King Tut’s tomb. This might be explained by reports that, when first opened, the walls of the tomb and the treasures therein were covered with thick, black mold.

Conditions Right for Mold Growth

Mold can grow anywhere there is an edible, organic material and sufficient moisture. Mold can grow in a huge variety of environments: we are most familiar with mold that grows in warm, damp conditions, but some mold varieties can withstand very high temperatures, while other mold varieties can thrive in extremely cold conditions. There is even a mold variety called “dry rot” that can grow with very little moisture.

How Mold Spreads

Like all members of the fungi kingdom, mold is saprophytic, getting its nourishment from the breakdown of other organic material. Mold and other fungi are important in the Earth’s ecology because they help decompose other organic matter.

Mold colonies send out thread-like filaments that release enzymes to break down and absorb nutrients; when enough food is present, the filaments become wider and rounder, forming a patch of mold. Spores will develop on the ends of some filaments. When these tiny, durable mold spores are fully developed, the filaments release them into the air, where they are carried by air currents or anything they come into physical contact with. Mold spores are hearty and can survive even hot, dry conditions.

When a mold spore lands where conditions for mold growth are appropriate, it will send out its own filaments and begin the process again.

Danger in the Mold Life Cycle

Mold can cause a variety of health problems. In sensitive individuals, mold spores can cause a severe allergic reaction resulting in itchy eyes, nasal congestion, and even breathing difficulties. Mold spores also can be inhaled, and in some cases will grow into an internal fungal infection by forming a fungal ball in the lungs.

Established mold colonies are living things, and like all living things, they eat and excrete. Mold eats the surface upon which it grows, along with water, and excretes a digested form of that material. In some mold varieties, the excretion is a highly toxic compound called a mycotoxin. Mycotoxins can be absorbed through the skin and can cause rashes and irritation; they also can be inhaled. Inside the body, mycotoxins can wreak havoc with the human nervous system. Some mycotoxins suppress the immune system, and some are considered potent carcinogens (cancer-causing agents).

Humidity and Mold

Any indoor area where the relative humidity is at or above 55 percent presents the potential for toxic mold growth. Bathrooms and kitchens, where water is often in use, are likely to be the most humid rooms in any home. Basements and crawl spaces might also have high humidity levels. Rooms with houseplants or water features, such as aquariums or fountains, may exceed the 55 percent relative indoor humidity level that encourages mold growth.

Detecting and Monitoring Humidity

Humidity sensors, also called moisture meters, are available in many hardware stores for less than $20. These meters provide a continual digital readout of the amount of moisture in the air. Experts suggest you monitor humidity levels in:

• Every kitchen and bathroom, especially near sinks and toilets
• The attic, especially between the roof and the ceiling
• Inside wall cavities, especially if there has ever been water damage
• The basement and any crawl spaces
• Inside closets, pantries, and cabinets
• Inside heating/air conditioning ductwork, especially near the filter

Toxic Mold and Ventilation

Mold grows best in areas where moisture becomes trapped, such as behind wallpaper, or between a piece of furniture and a damp wall. The solution to controlling indoor mold is to provide ventilation that keeps air moving and gives humidity a chance to evaporate. Every living space must have a means to take in and release air; storage spaces can be vented or modified to allow air circulation and prevent moisture buildup.

Experts suggest you control indoor humidity by:

• Adjusting ventilation so the intake is slightly higher than the exhaust, creating a slightly higher level of air pressure inside than outdoors.
• Providing ventilation to outside for appliances such as clothes dryers and range hoods. Every combustion appliances, including stoves, fireplaces, and furnaces, create some moisture.
• Maintaining duct work and ventilation systems, sealing cracks and keeping doors tight-fitting, and fans fully operational.
• Store firewood outside the living space.

Toxic Mold and Dehumidifiers

In areas where the relativity humidity cannot be brought down below 55 percent by ventilation alone, dehumidifiers can help. These appliances use fans to pull moisture from the air, then condense and store the water in sealed tanks, which you can carry outside the house for disposal. Dehumidifiers come in a range of sizes. Experts say several small units at various locations in the home are more effective than one central unit. Basement and bathroom dehumidifiers are often most effective.

Air conditioners serve as a sort of dehumidifier by condensing water and shuttling it outside. Running a window air conditioning unit can help lower indoor relative humidity. Be sure the air conditioning unit is properly vented so water drains outside and away from the house.

Mycotoxins are dangerous to everyone, even those without mold allergies. When the invisible spores of toxic mold are inhaled, the mycotoxins can begin to affect the lungs and nervous system.

The Deadliest Molds

In order of danger, the toxic molds are:

Stachybotrys chartarum

Stachybotrys mold looks greenish-black and grows on moist material containing cellulose, such as wood, wallpaper, and the paper covering of drywall. It does not grow on concrete. Most people become exposed to Stachybotrys by inhaling its spores, but it also can cause serious problems through skin contact. Symptoms of mold poisoning with Stachybotrys include respiratory problems, flu-like symptoms, headache, nausea, fever, nose bleeds, and skin rashes. Stachybotrys mycotoxins are thought to be extremely potent carcinogens and can suppress the immune system.

Aspergillus

The Aspergillus family of molds — more than 160 varieties — are found mostly in decomposing or rotting organic material. Aspergillus infections often require hospitalization and long-term medical treatment.

• Aspergillus fumigatus can thrive in relatively high temperatures, it often infects compost materials. It can cause an allergic reaction in those who handle decomposing materials.
• Aspergillus niger can invade the body by being inhaled, where it can cause a “fungal ball” to grow in the lungs.
• Aspergillus flavus can produce an aflatoxin — a deadly mold byproduct — in foods that is a potent carcinogen when ingested. Aspergillus flavus that grows on peanuts can produce an aflatoxin linked to cancer in human beings. Aspergillus flavus that grows on animal feed can produce an aflatoxin that can instantly kill animals that eat the contaminated feed.

Cladosporium

Cladosporium mold is generally dark green on top and black underneath, with a velvet texture. Cladosporium grows on plants, food, soil, painted surfaces, and cloth, and can even grow on fiberglass. Physical contact with Cladosporium can cause skin and nail infections. Breathing in Cladosporium spores can cause lung disease and lead to emphysema after long exposure.

Fusarium

Fusarium usually lives in soil but is also often found in humidifiers and air conditioning systems, as well as water damaged building materials. Touching Fusarium can lead to skin and eye infections. Absorbing Fusarium spores through the skin or through breathing can lead to a hemorrhagic syndrome that causes excessive internal bleeding. Fusarium can produce mycotoxins called tricothecenes that can cause acute intestinal flu-like symptoms and can attack the female reproductive organs.

Penicillium

Penicillium grows on decaying organic material but can also live on painted surfaces and fiberglass duct lining. One form of Penicillium mold has been distilled into a useful antibiotic; but many people are allergic to the mold. In sensitive individuals, Penicillium can cause an acne-like skin condition as well as kidney infections, intestinal infections, and endocarditis (infection of the lining of the heart). People with weak immune systems, such as those undergoing chemotherapy or infected with HIV, are most likely to suffer serious side effects from Penicillium exposure.

Other molds that produce dangerous mycotoxins include Acremonium, Alternaria, and Chaetomium. But molds can have different appearances depending on the surface and conditions where they grow. The only way to know if you have a dangerous mold type is to have it tested.