There are many substances that can polluteindoor air. One that has received much mediacoverage recently is mold. While some molds

(such as the ones responsible for producing cheeseand penicillin) are beneficial, others may be a seri-ous health threat. Molds are fungi that producemicroscopic cells called spores. Mold spores arepresent everywhere both outdoors and indoors andspread easily through the air.

The most common “problem” mold in indoorenvironments is Stachybotrys atra (also called S.chartarum).

It is a black mold that grows on wet materialscontaining cellulose. Stachybotrys is one of severalmolds that produce potent mycotoxins (toxic sub-stances).

How does mold affect health?Most people have few difficulties when exposed

to mold spores, but it is estimated that about 10 per-cent of the population is severely allergic to mold.Symptoms include respiratory problems, nasal andsinus congestion, watery eyes, sore throat, coughingand skin irritations. Mold also can trigger asthmaattacks. In some cases reactions are fatal.

Children (especially infants), elderly persons,pregnant women, people with respiratory problems,and those whose immune systems are impaired areat higher risk from mold exposure. Even personswho have no ill effects at first may develop an aller-gy to mold after continued exposure. Therefore,everyone should avoid exposure to mold spores.

How do you know if you have mold?To grow, mold needs a food source, moisture, and

mild to warm temperatures. When mold spores inthe air find the right conditions they begin to grow.

The food source can be any organic materialsuch as dust, books, papers, animal dander, soapscum, wood, particle board, paint, wallpaper, carpetand upholstery. When such materials stay damp(especially in dark areas with poor air circulation)mold will grow. Flooding, pipe leaks, leaky roofs,moisture in walls, high indoor humidity, condensa-tion, and poor heating/air-conditioning systemdesign and operation can create the damp environ-ment mold needs to grow.

E-3326-02

MoldAn Indoor Air Pollutant

Janie L. HarrisExtension Housing and Environment Specialist

The Texas A&M University System

This antique bed and the wall behind it show significant molddamage.

If you can smell a musty odor or see mold, youhave a mold problem. If you suspect you have amold problem, you should thoroughly examine yourhome. It is important to know where to look.

Look for mold wherever there may be water dam-age—behind and under cabinets, around plumbingfixtures and appliances, under carpet, inside walls,behind baseboards and in attics. Moisture can seepthrough concrete walls and floors and cause moldgrowth on or in walls, carpeting and materialsstored in a basement. Mold also can grow behindfurniture (particularly if it is against an outside wall)and in closets with outside walls.

Signs of water damage include stains, peelingpaint, and damp flooring or carpet. To prevent moldgrowth, water-soaked areas should be dried within24 hours.

In some cases it may be worthwhile to have theair in your home tested for mold spores even if youfind no visual evidence of mold. Accurate testingcan be expensive because it requires special equip-ment and training. However, if a family member hasan unexplained illness, testing can determinewhether high levels of mold in the home might bethe cause.

How do you remove mold?Small areas of mold (less than a few square feet)

can be cleaned by the homeowner. Larger areasshould be examined by an experienced health andsafety professional and treated by personnel withtraining and experience in handling contaminatedmaterial.

The first step in cleaning up mold is to dampenmoldy areas by misting them with water to mini-mize the number of spores that become airborne.Then, clean mold from hard surfaces such as hardplastic, glass, metal and counter tops by scrubbingwith a non-ammonia soap or detergent. (Do not mixbleach and ammonia because the fumes are toxic.)It is impossible to remove mold completely fromporous materials such as paper, sheetrock (drywall)and carpet padding, so these materials should beremoved and discarded.

Scrubbing probably will not remove mold com-pletely from structural wood such as wall studs, sothese areas will need to be sanded and sealed.

After the mold has been removed from non-porous surfaces, disinfect the area with a solution ofbleach and water (or another disinfectant). A solu-tion of 1/4 cup bleach to 1 gallon of water shouldwork for clean surfaces (those with no remaining

mold). For surfaces that can not be completelycleaned, the solution should be about 1 1/4 cupsbleach to 1 gallon of water. Apply the bleach solu-tion with a sponge or spray bottle. Leave it on thesurface for 15 minutes so that any remaining moldwill be killed. Then rinse the area with clean waterand dry it as rapidly as possible. Use fans, dehumidi-fiers or natural ventilation (if the outside air is dry).As a last step, contractors may seal the surface witha product containing a fungicide. This encapsulatesany mold spores that remain on the surface. Thissealing is especially important for wood beams,floor joists, wood studs, etc.

Throughout the mold removal process, protectyour health by wearing a mask or respirator to filterout mold spores. Protective gear is usually designat-ed as an N95, 3M #1860, or TC-21C particulate res-pirator. Wear eye protection, rubber gloves andclothing that can be laundered immediately orthrown away.

Thoroughly ventilate the work area with outsideair. Seal off the mold removal area from other partsof the home that are not contaminated, and keepother people out of the work area.

How do you control mold growth?Studies have found that mold contamination can

be greatly reduced if a home is kept dry and clean,and efforts are made to reduce the level of moldspores entering the home.

Controlling moisture. To control mold for good,you must solve any moisture problems in yourhome. Because there are mold spores everywhere,and mold grows on any wet, organic surface, theonly way to prevent mold growth is to keep thingsdry.

The floor joists of homes on pier-and-beam foundationsoften become moldy because of exposure to moisture.

� Keep the relative humidity as low as possible,within a range of 30 to 50 percent.

� Clean and dry damp areas such as plumbingand floors under sinks, around washingmachines, and around toilets and faucets. Drycondensate on window frames. Clean and dryrefrigerator and freezer drip pans and doorgaskets. Wipe up spills immediately. Keep therefrigerator clean and free of mold.

� Fix plumbing and roof leaks immediately, andinspect these areas routinely. Dry water-dam-aged areas within 24 hours. If flooding isextensive, obtain the help of a trained, certifiedrestoration specialist. Wet drywall, insulationand carpet must be removed.

� Have your heating/air-conditioning systemserviced annually. Make sure the technicianchecks for standing moisture and contamina-tion and cleans the coils. He should also cleanthe ductwork and drain pan, and replace themwhen necessary.

� Make sure water drains away from the house,not under the slab or crawl space. The crawlspace of a home on a pier-and-beam founda-tion should have cross ventilation to help keepthe area dry. Check for plumbing leaks in thecrawl space and repair any you find.

Cleaning. Regular cleaning and disinfecting canhelp prevent mold problems.

� Use a disinfectant on floors and countertops.

� After cleaning moisture-prone surfaces inkitchens and bathrooms, spray them with analcohol-based spray or disinfectant.

� Dry tub, shower and shower curtains aftereach use, or apply a product that prevents

mildew growth. If shower curtains and linersbecome mildewed, replace them.

� Clean and disinfect garbage and trash cans atleast weekly, and use disposable liners.

� Have carpets and upholstery professionallysteam cleaned periodically. Vacuum oftenusing a vacuum cleaner with a HEPA (high-effi-ciency particulate air) filtered exhaust anddouble-wall dust collection bags. A central vac-uum cleaner system is best because it exhaustspollutants outside the home.

� Launder area rugs frequently.

� Vacuum upholstery and mattresses at leasttwice a month.

� Vacuum blinds and curtains often.

� Clean behind stoves and refrigerators regularly.

Reducing mold spores in the home. There area number of things you can do to reduce the num-ber of mold spores that enter your home.

� Place mats at each doorway to prevent mold-contaminated soil and debris from beingtracked inside.

� Inspect building materials for mold beforebringing them into the home. Lumber, drywalland other materials are often stored improper-ly and can harbor mold.

� Replace carpet with hard surface flooring.

� Replace upholstered furniture with leather orvinyl furniture.

� Use foam or rubber mattresses, or encase mat-tresses in plastic coverings that can be cleanedand disinfected.

� Eliminate houseplants and indoor pets. Soilcontains mold spores, and pets track in mold.Pets’ food and water trays also can harbormold.

� Have the heating/air-conditioning ductworkinspected and sealed, especially if it is locatedin the crawl space under the house. A leakysystem can pull mold spores into the house.

� Cover the soil in the crawl space, and makesure condensate and other water drains awayfrom the house. For heating/air-conditioningsystems located in attics or closets, check tomake sure condensate drip pans drain into theplumbing system and that the emergencydrain is open and operating. These moldy pictures and frames have been removed for

cleaning.

Will air cleaners remove mold spores?Air cleaners will not solve a mold problem. A

high-efficiency air filter may reduce the number ofspores in the air, but it can not remove spores thathave settled on floors and other surfaces. TheEnvironmental Protection Agency reports that aircleaners that produce ozone are not effective ateliminating mold and other air contaminants.Furthermore, ozone is a lung irritant that should notbe in an occupied space.

Will ultraviolet light kill mold spores?UV light does destroy any viruses, bacteria and

fungi in air that passes through its path, but manymold spores are not airborne and will never passthrough an air duct UV light system.

For further information:“Healthy Indoor Air for America’s Homes—Bugs,

Mold and Rot,” Montana State UniversityCooperative Extension.

“Health Effects of Mold,” publication AE-1202, NorthDakota State University Extension Service.

“Are ozone generators effective in controlling pollu-tion?” Environmental Protection Agencyhttp://www.epa.gov/iaq/pubs/ozonegen.html

Texas Cooperative Extension, Housing andEnvironment Program on Indoor Air Quality http://fcs.tamu.edu/housing

Texas Cooperative Extension, Prevention ofHousehold Mold http://stephenville.tamu.edu/~clee/bmold.html