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Public Health Officials Warn of Flooding’s Delayed Dangers

For release: Immediate     Date: Oct. 27, 2010
Contact: Bill Furney 919-715-4174

Raleigh -- Coastal residents working on or living in buildings damaged by water during recent flooding should be aware of the potential for biological contamination, industrial hygienists with the state Division of Public Health warn.

If conditions are favorable, microscopic organisms such as fungi (mold) and bacteria can germinate and colonize materials, contents and furnishings long after the initial cleanup is completed. People who live and work in contaminated buildings run the risk of developing potentially serious illnesses such as asthma and allergic rhinitis.

Porous, soft or spongy materials such as carpet, upholstered furniture, sheetrock and bedding that are soaked by floodwater or rainwater dry very slowly. With sufficient moisture, microorganisms can reproduce in numbers that can present a health risk after only 48 hours. The only way to prevent this growth is to quickly dry affected materials. Once the materials have been colonized they must either be thoroughly cleaned and dried or disposed of. Remember that floodwaters are contaminated with soils and dissolved organic matter that are excellent nutrient sources for microbial growth and remain as residues if the affected materials are only dried. Actual cleaning (scrubbing) is necessary.

The following guidelines are recommended for cleanup activities:

  • Porous or spongy materials that remained wet for more than 48 hours should be cleaned throughout or thrown away.
  • Nonporous and semi-porous materials that are structurally sound can be cleaned. They should be scrubbed and washed with a detergent solution to remove soils, contaminants and bio-films and rinsed with clean water. An optional disinfectant solution such as 2 cups of household bleach mixed with one gallon of water may be applied to affected materials after cleaning. Follow the label instructions, use in ventilated areas and wear gloves and eye protection. Some materials, such as textiles, may be damaged by bleach solutions. Remember that disinfectants are only effective on clean surfaces and the use of a disinfectant is no substitute for cleaning and drying affected materials.
  • Fungi and bacteria will continue to grow in and on materials if they remain wet even after very thorough cleaning and disinfecting. Make sure the materials are dry after cleaning. If affected materials contents and furnishings cannot be dried out, throw them away.
  • If wall to wall carpet and drywall become moldy or musty smelling, they are probably contaminated and should be discarded. Carpet cleaning professionals using hot water extraction methods may be able to clean valuable area rugs.
  • Contaminated upholstered furniture, bedding, and books are much more difficult to clean than carpet and should usually be thrown away because cleaning may be more expensive than replacement.
  • Handling and cleaning contaminated materials can result in significant exposures to mold spores, fragments, irritants and allergens. Individuals with respiratory allergies, or other respiratory illnesses, should not handle or disturb materials that have visible mold growth. Professional cleaning companies using appropriate personal protective equipment should be used if contamination is extensive.

More information about Mold and Human Health can be found at the Division of Public Health’s Occupational and Environmental Epidemiology Branch website at
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