Flooding and indoor air quality

Boulder Colorado recently experienced a 100-y flood, and some parts of the front range were even hit by a 500-y event.  All that moisture and organic material causes serious indoor air quality problems; extensive water damage after hurricanes and floods increases mold contamination in buildings  (Fabian et al. 2005; Riggs et al. 2005; MMWR 2006). The CDC recommends that in homes that have been wet for more than 2 days, remediation should occur quickly and exposure to mold-contaminated materials can cause adverse health effects in susceptible persons (MMWR 2006).


Mold from a flooded home (http://www.markshomeinspection.com/blog/)

After Hurricanes Katrina and Rita in New Orleans, visible mold growth was documented in 44% of the residences (Riggs et al. 2005), elevated air concentrations of mold spores were measured outdoors and indoors (Solomon et al. 2005), and endotoxin levels were elevated in water-damaged homes (Rao et a. 2007).

Mold has been associated with nasal and throat symptoms, cough, wheeze, asthma exacerbations in sensitized asthmatics, and hypersensitivity pneumonitis (IOM 2004).  Building dampness and mold was associated with 30-50% increases in a variety of respiratory and asthma-related health outcomes (Fisk et al. 2007). Asthma incidence increased after flooding in North Carolina due to Hurricane Floyd (MMWR 2000).  Respiratory illness and asthma exacerbations following flooding in New Orleans was found to be positively associated with exposure to water-damaged homes; exposure included just being inside and not participating in any clean up activities.  Subsequently the use of respirators has been strongly recommended when inside water damaged homes. Air cleaners and N95 masks may also be helpful.  Good ventilation is essential.

Remediation efforts after flooding include disposal and replacement of damaged furnishings and drywall, cleaning surfaces, drying remaining structure, and treatment with a biostatic agent (Chew et al. 2006).  Reports differ on whether remediation efforts are successful at reducing indoor concentrations of microorganisms.  Fabian et al (2005) reported that indoor levels remained elevated in remediated homes compared to outdoors. Whereas Chew et al. (2006) reported that indoor levels were mostly reduced compared to before remediation and outdoors. Improved remediation methods would be essential to reducing exposure and health effects after flooding and to help residents move back into their homes quickly.

Be careful out there, Boulder and front range communities, as you courageously deal with the aftermath of the flood.  More information about floods and indoor air quality can be found at http://www.bouldercounty.org/flood/health/pages/flair.aspx.


  • Fabian MP, Miller SL, Reponen T et al. 2005. J Aerosol Sci 36:763-783.
  • Riggs MA, Rao CY, Brown CM et al. 2008. Environ Res 106:401-409.
  • MMWR 2006. 55:231-234.
  • Solomon WR 1975. J Allergy clinical Immun 56:235-242.
  • Rao CY, Riggs MA, Chew GL et al. 2007. Appl Environ Microbiol 73:1630-1634.
  • IOM 2004. Damp Indoor Spaces and Health. The National Academies Press, Washington, DC.
  • Fisk WJ, Lei-Gomez Q, Mendell MJ 2007. Indoor Air 17:284-296.
  • MMWR 2000. 49:369-372.
  • Chew GL, Wilson J, Rabito FA et al. 2006. Environ Health Perspect 114:1883-1889.