The paper – the first scientific study of New Orleans air quality since Hurricane Katrina – was published by a team of researchers from the University of Colorado, Boulder; University of California, Berkeley; and the Natural Resources Defense Council (NRDC). The researchers did the study in collaboration with New Orleans community groups.
"The mold levels we found across the city could easily trigger serious allergic or asthmatic reactions in sensitive people," said Dr. Gina Solomon, M.D., the NRDC senior scientist who led the research team. "The indoor air quality in the flooded homes was particularly worrisome, but fortunately, the homes that had been fully gutted and cleaned up did appear to have lower levels."
Federal agencies, including the Environmental Protection Agency (EPA), Department of Health and Human Services (HHS) and the Centers for Disease Control and Prevention (CDC), have not monitored mold levels in areas that flooded, and have not helped residents cope with the mold problem, prompting Solomon to say: "Although there are no U.S. regulatory standards for either indoor or outdoor levels of mold spores, it is the government's responsibility to ensure the public is protected from the dangerous health risks."
Mold growing on damp surfaces releases spores that can be inhaled. Some molds also produce chemicals known at mycotoxins that may be toxic 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 fevers and makes it hard to breathe). Some studies have shown that outdoor levels of mold spores are directly associated with childhood asthma attacks.
The scientists collected air samples for mold spore analysis at 23 outdoor and eight indoor locations across the New Orleans metropolitan area in October and November of 2005. They chose sites representing varying degrees of flooding, and some of the indoor sites had undergone remediation. Sampling times ranged from 6 to 24 hours.
The levels of airborne mold spores were extremely high both inside and outside of homes, especially in the areas that flooded. The mold concentrations outdoors ranged from 21,000 to 102,000 spores per cubic meter (m3). The average outdoor spore concentration in flooded areas was double the concentration in non-flooded areas. The researchers also reported the peak mold spore concentrations over a 30-minute period. The highest outdoor 30-minute concentration was 259,000 spores m3.
The National Allergy Bureau of the American Academy of Allergy and Immunology considers any outdoor mold spore level of greater than 50,000 spores m3 to be "very high." The spore counts outdoors in 77 percent of the samples taken in flooded neighborhoods – including New Orleans East, Lakeview, Gentilly, the Lower 9th Ward, Chalmette, Uptown, Mid-City and the Garden District – exceeded 50,000 spores m3. Background mold spore concentrations in Louisiana during that same time period ranged from about 16,000 to 24,000 spores m3.
The highest concentrations were inside homes, where levels ranged from 11,000 to 645,000 spores m3. The 30-minute peak concentration was more than 1 million spores m3. The researchers identified 45 different types of mold in the sampling. The most common molds were Cladosporium and Aspergillus/Penicillium. They also detected Stachybotrys (often called "toxic mold") in some indoor samples.