Mold and endotoxin levels in the aftermath of Hurricane Katrina: a pilot project of homes in New Orleans undergoing renovation

Abstract

Background: After Hurricane Katrina, many New Orleans homes remained flooded for weeks, promoting heavy microbial growth.

Objectives: A small demonstration project was conducted November 2005-January 2006 aiming to recommend safe remediation techniques and safe levels of worker protection, and to characterize airborne mold and endotoxin throughout cleanup.

Methods: Three houses with floodwater lines between 0.3 and 2 m underwent intervention, including disposal of damaged furnishings and drywall, cleaning surfaces, drying remaining structure, and treatment with a biostatic agent. We measured indoor and outdoor bioaerosols before, during, and after intervention. Samples were analyzed for fungi [culture, spore analysis, polymerase chain reaction (PCR)] and endotoxin. In one house, realtime particle counts were also assessed, and respirator-efficiency testing was performed to establish workplace protection factors (WPF).

Results: At baseline, culturable mold ranged from 22,000 to 515,000 colony-forming units/m3, spore counts ranged from 82,000 to 630,000 spores/m3, and endotoxin ranged from 17 to 139 endotoxin units/m3. Culture, spore analysis, and PCR indicated that Penicillium, Aspergillus, and Paecilomyces predominated. After intervention, levels of mold and endotoxin were generally lower (sometimes, orders of magnitude). The average WPF against fungal spores for elastomeric respirators was higher than for the N95 respirators.

Conclusions: During baseline and intervention, mold and endotoxin levels were similar to those found in agricultural environments. We strongly recommend that those entering, cleaning, and repairing flood-damaged homes wear respirators at least as protective as elastomeric respirators. Recommendations based on this demonstration will benefit those involved in the current cleanup activities and will inform efforts to respond to future disasters.

Figure 1

Results of filter samples from the three houses using three different analytical methods: total culturable mold (A; results are shown only for those grown on malt extract agar and cultured at 25°C), PCR (B), and endotoxin (C). Work for house 1 is the average of two measurements (upstairs and downstairs); outdoor prework is represented only by house 3; outdoor work is represented only by house 2; and outdoor postwork represents the average of the three houses.

Figure 2

Results of mold spore counts. Only house 1 had an inside postwork measurement. Outdoor pre-work and work levels represent the average of the measurements for the three houses. Spore counts for house 1 decreased 77.6% between prework and postwork periods.

Figure 3

Frequency of fungal taxa in samples of indoor and outdoor air from the three houses and during different timepoints grouped together. The sample size limited interpretation when stratifying by location and timepoints. Culture at 25°C (n = 35); culture at 37°C (n = 35); spore counting (n = 17); and PCR (n = 21).

Figure 4

Total particle concentrations before and during the renovation.

Figure 5

Size-selective particle concentrations before (A) and during (B) the renovation.