Academic journal article Environmental Health Perspectives

Airborne Mold and Endotoxin Concentrations in New Orleans, Louisiana, after Flooding, October through November 2005

Academic journal article Environmental Health Perspectives

Airborne Mold and Endotoxin Concentrations in New Orleans, Louisiana, after Flooding, October through November 2005

Article excerpt

BACKGROUND: The hurricanes and flooding in New Orleans, Louisiana, in October and November 2005 resulted in damp conditions favorable to the dispersion of bioaerosols such as mold spores and endotoxin.

OBJECTIVE: Our objective in this study was to assess potential human exposure to bioaerosols in New Orleans after the flooding of the city.

METHODS: A team of investigators performed continuous airborne sampling for mold spores and endotoxin outdoors in flooded and nonflooded areas, and inside homes that had undergone various levels of remediation, for periods of 5-24 hr during the 2 months after the flooding.

RESULTS: The estimated 24-hr mold concentrations ranged from 21,000 to 102,000 spores/[m.sup.3] in outdoor air and from 11,000 to 645,000 spores/[m.sup.3] in indoor air. The mean outdoor spore concentration in flooded areas was roughly double the concentration in nonflooded areas (66,167 vs. 33,179 spores/[m.sup.3]; p < 0.05). The highest concentrations were inside homes. The most common mold species were from the genera of Cladosporium and Aspergillus/Penicillium; Stachybotrys was detected in some indoor samples. The airborne endotoxin concentrations ranged from 0.6 to 8.3 EU (endotoxin units)/[m.sup.3] but did not vary with flooded status or between indoor and outdoor environments.

CONCLUSIONS: The high concentration of mold measured indoors and outdoors in the New Orleans area is likely to be a significant respiratory hazard that should be monitored over time. Workers and returning residents should use appropriate personal protective equipment and exposure mitigation techniques to prevent respiratory morbidity and long-term health effects.

KEY WORDS: air quality, bioaerosols, endotoxin, flood, Katrina, mold, New Orleans. Environ Health Perspect 114:1381-1386 (2006). doi:10.1289/ehp.9198 available via [Online 12 June 2006]


Hurricane Katrina struck New Orleans, Louisiana, on 29 August 2005, breaching the levees that protected the city and flooding approximately 120,000 homes. Some homes remained underwater for weeks, and some neighborhoods were flooded again when Hurricane Rita struck on 22 September 2005. Flood damage varied throughout the city, with some areas spared and others flooded to the rooflines. There were immediate concerns about environmental health hazards ranging from oil spills and disruptions of hazardous waste sites, to sewage contamination in floodwaters (U.S. Environmental Protection Agency 2006). As the water receded, concerns related to air quality emerged--specifically, aerosolization of mold spores and endotoxin. A survey by the Centers for Disease Control and Prevention (CDC) in late October found that 46% of randomly selected homes in the New Orleans area had visible mold growth, and 17% had heavy mold coverage (CDC 2006).

Mold. Filamentous microfungi (mold) can threaten human health through release of spores that become airborne and can be inhaled. Some molds produce metabolites (mycotoxins) that can initiate a toxic response in humans or other vertebrates (Robbins et al. 2000). Repeated exposure to significant quantities of fungal material can result in respiratory irritation or allergic sensitization in some individuals (Bush et al. 2006). Sensitized individuals may subsequently respond to much lower concentrations of airborne fungal materials. Of the thousands of types of fungal spores found in indoor and outdoor environments, adverse health effects in humans have most frequently been associated with Alternaria, Aspergillus, Cladosporium, Penicillium, and Stachybotrys (Hossain et al. 2004; Jarvis and Miller 2005; O'Driscoll et al. 2005; Stark et al. 2003).

In outdoor air, elevated concentrations of fungal spores are associated with allergic and asthmatic responses in humans. A large Canadian time-series study reported that daily fluctuations in ambient mold spores are directly associated with childhood asthma attacks requiring a visit to an emergency department (Dales et al. …

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