Scrubbing Moldy Walls Will Not Protect Families in Badly Flooded Homes

NEW ORLEANS (December 28, 2005) -- The only way that Gulf Coast residents with badly flooded homes may be able to protect themselves from dangerously high mold levels is to rip out contaminated drywall to the studs, according to the Natural Resources Defense Council. New NRDC tests of mold-contaminated New Orleans homes show that merely removing furniture and carpeting and scrubbing down mold-covered walls will not safeguard residents' health. (See detailed recommendations.)

"Seriously flooded homes are likely to remain dangerous unless they are gutted to the studs," said Dr. Gina Solomon, M.D., who led the NRDC research team. "But homes that were briefly flooded with less than a few inches of water and have no visible mold probably don't have a serious mold problem."

Federal, state and local agencies have not released any sampling results for mold in flooded areas, and are not doing enough to help residents cope with the mold problem, according to NRDC. Although there are no U.S. regulatory standards for either indoor or outdoor levels of mold spores, the group says it is the government's responsibility to ensure the public is protected from this dangerous health risk.

"I am getting questions from people who are trying to decide whether it is safe to move back to their homes," said Pam Dashiell, president of the Holy Cross Neighborhood Association in the Lower Ninth Ward. "But there is no information from FEMA, EPA, or anyone else about whether it is safe. This new information will help people to protect themselves from asthma and other health problems."

NRDC collected air samples for mold spore analysis at locations across the New Orleans area in mid-October, and went back for follow-up tests in mid-November. Indoor mold levels were extremely high in homes where there had been no cleanup or where there had been only partial cleanup, while mold levels in homes that had been thoroughly cleaned and where carpeting and drywall had been removed were comparable to corresponding outdoor mold levels.

New Mold Test Results

Recent scientific studies consider houses with indoor mold spore counts higher than 1,300 spores per cubic meter (spores/m3) to be "moldy homes" that can cause health problems. All of the New Orleans homes tested by NRDC had mold spore counts far above this level. Indoor mold concentrations are normally far lower than outdoor levels, so the NRDC researchers compared indoor and outdoor levels at the same locations to help gauge the severity of the contamination.

Last October, the NRDC team found extremely high mold spore levels in a flooded house in Mid-City that still had moldy furniture, carpets and drywall in place. The house had mold spore concentrations of 650,000 spores/m3, which would render it dangerously uninhabitable.

In October and November, the NRDC team tested air quality in three homes that had been partially cleaned up. Contaminated furniture and carpeting had been removed, as had some moldy drywall. Other walls had been scrubbed with bleach. These houses had average mold spore concentrations of 377,000 spores/m3, still dangerously high.

In November, NRDC tested the air in two houses where all furniture and carpeting had been removed, all drywall had been ripped out down to the studs, and the interior had been aired out. The houses had average mold spore counts of 72,000 spores/m3, nearly the same as the outdoor air the team tested at the same locations.

The November tests also found the air in two houses in Uptown and Mid-City that had suffered only minimal flooding (flooding of the crawl space, or less than 3 inches of water for a brief period in the living space) averaged only 11,000 spores/m3, which was considerably lower than outdoor air samples the team took at the same locations.

Mold Can Pose a Serious Health Threat

Mold growing on damp surfaces releases spores that can be inhaled. Some molds also produce chemicals known at mycotoxins that may be dangerous to humans. Mold can cause congestion, sneezing, runny or itchy nose, and throat irritation; more serious symptoms include major allergic attacks, cough, asthma attacks, and hypersensitivity pneumonitis (a pneumonia-like illness that causes breathing difficulty and fever).

In the flooded houses tested by NRDC, the dominant mold types were Aspergillus/Penicillium, some species of which are known to cause health problems. In four of the flooded homes -- including one of the fully cleaned homes -- NRDC also detected airborne spores of Stachybotrys species, which also is known as "black mold" or "toxic mold." Stachybotrys is known to produce mycotoxins, and some scientists have associated it with neurological, immune system, and other serious health problems.

Cleanup Recommendations

Experts say that anyone doing clean-up or debris removal in a moldy environment should wear nitrile gloves, a respirator (such as an N95 or N100 mask), safety glasses, shoe covers, and a Tyvek suit over clothing. Decreasing indoor moisture is the most critical factor for controlling mold growth. Windows and doors should be opened for ventilation, and fans can be used to provide additional air flow. Dehumidifiers also may help prevent further mold growth.

All non-cleanable items that have been wet for more than two days or that have visible mold should be thrown away. Non-cleanable items include mattresses, carpeting and carpet padding, rugs, stuffed animals, upholstery, wallpaper, drywall, floor and ceiling tiles, insulation material, clothing, leather, paper, soft plastics, and wood. Mold-covered drywall is definitely not salvageable, and the most recent NRDC test samples suggest that seriously flooded structures need to be stripped to the studs.

NRDC's tests did not evaluate different types of treatment for stopping mold growth in the studs themselves. In addition, the group cannot ensure that mold will not eventually grow back in fully gutted homes. Future testing will be needed to determine that cleaned up homes remain safe over the long term. (For more specific information about ways to protect families from mold and safely remove it, go to

Related NRDC Pages
New Orleans Environmental Quality Test Results