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Aug. 20, 2014

MSU expert: Protect yourself from floodwater contamination

Recent torrential rainfall across the United States has led to flash flooding, filling basements with water and sewage that can contain hundreds of pathogens. Joan Rose, Michigan State University's Homer Nowlin Chair in water research, advises that residents should assume floodwaters are contaminated and that exposure to these waters may raise the risk of diarrhea, dysentery, hepatitis, skin and eye infections, and respiratory disorders.

The first step  is to remove floodwater and sewage and dry the affected area, according to Rose. Fans and enhanced ventilation are helpful tools for drying damp structural surfaces. Disinfecting these areas also is important.

“It is important to evaluate items contacted by floodwaters, deciding what to discard and what to keep,” Rose said. “Whenever possible, a disinfecting solution of water and chlorine bleach should be applied to the surfaces of saved items.”

Joan Rose is an international authority on water microbiology, water quality and public health safety. She can speak on waterborne disease outbreaks and the study of water supplies, treatment, and reclamation. Her applied research also includes the study of microbial pathogens in recreational waters and climatic factors affecting water quality. She can be reached at (517)-432-4412 or

To help prevent disease transmission associated with flood cleanup, Rose offers the following tips. When using a disinfecting solution to clean after a flood, remember to:

  • Wear gloves and protective clothing. Do not touch your face or eyes.
  • Change the disinfecting solution often and whenever it is cloudy.
  • Be thorough. Wash and dry everything well.
  • When finished, wash your hands thoroughly with soap and water for at least 20 seconds, even if you have worn gloves.
  • If an item got wet, assume it is contaminated.
  • Disinfecting works best when all loose dirt and debris are removed first.
  • Use a disinfecting solution (3/4 cup regular strength chlorine bleach or 1/2 cup concentrated bleach to one gallon of water) to disinfect walls, floors and other surfaces touched by floodwaters. Keep the area wet for at least two minutes, then rinse thoroughly and dry.
  • Carpets and rugs that have been soaked for more than 24 hours should be discarded. If carpets and rugs were soaked for less than 24 hours, evaluate as follows: Carpets that contacted sewage-contaminated floodwater should be discarded. Carpets contacted only clean basement seepage or lawn runoff into a sub-basement, for example, may be dried and cleaned. Washable throw rugs usually can be cleaned adequately in a washing machine.
  • When addressing exterior surfaces, such as outdoor furniture, patios, decks and play equipment, keep surfaces wet for 10 minutes (this may mean wetting the surface more than once), then rinse thoroughly and dry.
  • Chlorine bleach solutions degrade quickly. Be sure to make a fresh solution daily as needed. Unused solution may be discharged into toilet or sink.
  • Contaminated clothing should be washed in the hottest possible water with detergent and chlorine bleach if fabric instructions permit.

By: Mackenzie Kastl