Fungus Among Us: Find Out the Causes of Mold and How to Prevent Mold Growth

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In February 2001, a Foresthill, California, family burned their house down to get rid of mold. In May 2002, the Delaware Supreme Court upheld a $1 million award to two women whose landlord failed to address leaks and mold problems in their apartments, resulting in asthma attacks and other health problems.

Why is mold suddenly such a huge issue?

Molds have been around since the beginning of time. There are more than 100,000 known living species of fungus, some of which are beneficial to humans (notably those used for making cheese and penicillin), and there may be as many as 200,000 more unidentified species.

Molds can be found in any dark and damp place, indoors or outdoors. The four types that are of most concern are Stachybotrys, Chartarum, Penicillium, and Aspergillus. These are present, in varying degrees, in almost every building we inhabit. According to the U.S. Environmental Protection Agency (EPA), “There is no practical way to eliminate all mold and mold spores in the indoor environment; the way to control indoor mold growth is to control moisture.”

Molds reproduce by creating tiny spores that drift through the air. These spores grow by digesting damp materials such as wood, paper, carpet, and foods. Mold needs very little to thrive: air, food, and moisture (liquid water isn’t necessary; most mold species need only 40 to 60 percent relative humidity). By increasing the amount of insulation and decreasing air leakage in houses, we have created more opportunities for mold to grow if moisture leaks into walls or floors. Also, homes built on concrete slabs will release moisture into the walls for years as they cure. Building materials that were left outside before use can harbor mold spores for many years.

Mold spores can be inhaled, absorbed through the skin, or ingested on food. While most people are not adversely affected, some–particularly infants, the elderly, and anyone with immune system deficiencies–are particularly susceptible to serious illness following exposure to microbial contamination. Common ailments from molds are asthma, pneumonia, upper respiratory problems, sinusitis, dry cough, skin rashes, stomach upset, headaches, disorientation, and bloody noses. A 1999 Mayo Clinic study cites molds as the cause of most of the chronic sinus infections that inflict 37 million Americans each year.

Molds also release mycotoxins when their food source is removed or they dry up. These mycotoxins can lead to severe illness. Some species of molds are also carcinogenic. In a few cases, severe exposure can lead to internal bleeding, kidney and liver failure, pulmonary emphysema, or even death, according to the American Lung Association and the EPA.

Do you have a mold problem?

Because mold occurs in all buildings, it’s difficult to identify the problem. Some individuals react badly to relatively small amounts of mold while others are tolerant of large amounts. The general rule of thumb is that if you can see or smell mold, you should remove it.

While home test kits and professional mold remediation services are available, most government agencies discourage testing as a first step. The California Department of Health Services does not recommend testing because “there are few available standards for judging what is an acceptable quantity of mold. Individual susceptibility varies so greatly that sampling is at best a general guide.”

What can you do?

The conventional method for killing mold on ceramic tiles and other non-porous surfaces is not the most environmentally friendly one. In many cases, spraying a mixture of bleach and water directly on mold and allowing it to sit for a couple of hours will effectively eliminate the organisms. However, bleach fumes are extremely harmful.

A less toxic approach is to spray a mixture of borax and water on the mold. In the shower, wash down the tiles with borax and do not rinse; the borax residue will fight mold growth. Tea tree oil, which has natural microbial properties, is also effective; mix two teaspoons with about two cups of water. White vinegar, poured directly onto mold, is also said to be about 80 percent effective.

In the most severe cases, you may need to remove the underlying sheetrock, studs, ceiling tiles, carpets, or other materials where mold has taken hold.

Once you have removed the mold, take the following measures to ensure that no new mold will grow.

Fix wet basements. Water entering the house through your basement can be corrected by redirecting the flows of stormwater, sloping the land away from the house, repairing and cleaning gutters and downspouts, and fixing cracks in the basement walls and floors, and in severe cases, waterproofing the outside walls of the foundation.

Fix leaking pipes. Water leaks in pipes or around tubs and sinks can lead to mold growth, particularly when the water seeps into wall and floor cavities.

Reduce condensation from crawl spaces. Put a plastic cover over dirt in the crawlspace to prevent moisture from entering the floor. Make sure the crawlspace is well ventilated.

Ventilate attics. Install roof and/or ridge vents, insulate the attic, and put a moisture barrier between the insulation and the floor.

Install exhaust fans and vents. Place these in bathrooms and kitchens to remove moisture to the outside (not into the attic). Vent your clothes dryer to the outside.

Reduce humidity. Open a bathroom window when taking a shower. Use a dehumidifier in the basement.

Repair or replace windows. Replace window glazing and install storm windows or replacement windows to reduce condensation buildup.

Increase internal circulation. Open doors between rooms, especially doors to closets with external walls, to increase circulation. Use fans and move furniture from wall corners.

Check carpet on concrete floors. Use a plastic vapor barrier and carpet pad or use area rugs that can be washed.

Install the right wallcovering. Avoid vinyl, which creates a watertight surface that can trap moisture in the drywall behind it.

What’s the bottom line?

It’s important to remember that everyone reacts differently to mold and that each home is different. Don’t rush out and spend a lot of money or buy expensive unproven remedies. In most cases, a thorough examination of your house, followed by the basic fixes identified above, should eliminate most mold causes and keep your home environment safe and worry-free.

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