Mold in the Home: Is it as Dangerous as You're Led to Believe?
Reprinted with permission from the Arizona
Department of Real Estate Bulletin April 2001

   Stories about Arizona homes infected with mold are appearing everywhere, in print and on television. Is there a real problem, or has the media blown everything out of proportion? How does this "mold mania" affect the real estate licensee?

Will Humble, an epidemiologist and Office Chief of the Arizona Department of Health Services' Environmental Epidemiology Section believes the problem is not as bad as you might be led to believe.

His advice to real estate licensees: "Do not hire someone to take samples in a home. They will find mold every time. The presence of mold revealed by sampling does not mean there is a mold problem in the house."

He suggests having a competent home inspector check the attic for water damage from a leaking roof, checking for musty odor in the house, and looking for obvious signs of water damage discolored walls or wet areas under sinks.

If a bedroom has a musty odor, ask whether the carpet has ever been flooded with water. If the water was not extracted immediately and completely, mold could have begun growing under the carpet. Drying the carpet does not remove dead mold spores, and re-wetting can cause mold growth to return. If there is heavy mold, the carpet may have to be replaced.

Mold in My Home: What Do I Do? is an information sheet published by the Department of Health Services' Office of Environmental Health. You can download a copy from their web site at   Look for the mold link in the last line of the last paragraph on the page.

Some excerpts from the Information Sheet:

Should I be concerned about mold in my home?

Yes, if the contamination is extensive. When airborne mold spores are present in large numbers, they can cause allergic reactions, asthma episodes, infections and other respiratory problems for people. Exposure to high spore levels can cause the development of an allergy to the mold. Mold can also cause structural damage to your home.

How can I tell if I have mold in my house?

If you can see mold, or if there is an earthy or musty odor, you can assume you have a mold problem. Look for previous water damage. Visible mold growth is found underneath materials where water has damaged surfaces, or behind walls. Look for discoloration and leaching from plaster.

Having a home sampled for mold and receiving a report that mold is in the home may stigmatize a home that actually has no problem. Mold inspection is an unregulated field, and lots of people are making money on mold. Humble cited a recent newspaper ad placed by a company recruiting mold inspectors. "Mold is Gold," the headline read.

To complicate matters, the Department of Health Services says "there are few available standards for judging what is an acceptable quantity of mold. In all locations, there are some outdoor levels of molds. If sampling is carried out, an outdoor air sample needs to be taken at the same time as the sample indoors to provide a baseline measurement. Since the susceptibility of individuals varies so greatly, sampling is at best a general guide."

Much has been made about the "deadly" Stachybotrys mold. It is dangerous, Humble said, but only in massive doses. "We don't talk about particular molds. The bigger problem overall is a person's sensitivity to mold."

The presence of mold in public schools has generated many headlines, and such stories have made some homeowners concerned about the possibility of mold in their homes. An example is Starline Elementary School in Lake Havasu City. The school has been closed because of extensive mold contamination. The cause of the problem was just what Humble said to look out for: a leaking roof. More than four years ago a contractor hired to replace the school's roof went out of business before the job was completed. The roof was not finished and during the next rainy season water flooded several classrooms. "The roof was never repaired properly and the mold grew from there," said the school's principal.

So what's the bottom line for the real estate licensee? If you see mold, smell mold's musty odor, spot the signs mentioned in the Department of Health Services' information sheet, or learn that one or more carpeted rooms may have been flooded, there may be a problem.

If your client asks whether the home should be sampled for mold, give them a copy of the information sheet and let them decide.

While any home will test positive for mold, a serious mold infection cannot be ignored. Some individuals are at a higher risk for adverse health effects, the Department of Health Services says. These include:

  • Infants and children

  • The elderly

  • Immune-compromised patients (people with HIV infection, cancer chemotherapy, liver disease, etc.)

  • Pregnant women

  • Individuals with existing respiratory conditions such as allergies, multiple chemical sensitivity and asthma.

Remediation of a serious mold infection can be very expensive five-figures expensive. Walls may have to be opened and even rebuilt. Structural damage may have to be repaired. Air conditioning and heating ducts may have to be replaced.

While the presence of mold in some structures may pose a significant health problem to susceptible individuals, the mere presence of mold is not necessarily something to be concerned about. If your client has concerns about mold, direct them to the Department of Health Services' information available on the Internet. Copies may also be obtained from the Office of Environmental Health, 3815 N. Black Canyon Highway, Phoenix, AZ 85018. You can telephone the office at 602/230-5830.

Also visit the Department of Real Estate's web site,, and navigate to the Table of Contents. There you'll find additional information from the Center for Disease Control and the State of California Environmental Health Investigations Branch.