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Human Risk Assessment: Floodwater Health Hazards

With all the national coverage of Hurricanes Harvey, Irma and Maria, viewers can see residents standing in and wading through waist deep floodwater. But have you ever wondered what hides in those murky waters? Companies, school officials, health officials and community leaders have to make decisions based on health and safety risk. Who do they turn to and what is the process that helps inform their decisions? The Risk Assessment process helps the decision makers make informed conclusions to protect you and others from the many hazardous substances that can be potentially found in floodwater.


  1. Water borne pathogens– Pathogens, such as Salmonella typhi, vibrio cholerae, campylobacter, Legionella, hepatitis A, giardia, and cryptosporidium, can contaminate potable or drinking water during a flood. An infection can occur when humans come into contact, inhale or drink the contaminated water. These pathogens are responsible for symptoms such as diarrhea, cramping, skin infections, pneumonia or fever and diseases such as typhoid fever, cholera, Legionnaire’s Disease, cellulitis, Hepatitis, giardiasis or cryptsporidiosis. You can also become infected with water borne pathogens, such as schistosomatidae, through contact of skin with contaminated waters. This can result in cercarial dermatitis, or commonly known as swimmer’s itch.


  1. Vector borne diseases– Mosquito populations flourish in stagnant water. After a flood, ponds of standing water in ground depressions, tires, debris, yard ornaments or backyard pools which have had no filtration due to power outages, can all act as a breeding ground for this pesky insect. The increased mosquito population can increase a person’s chances of contracting diseases like zika, malaria, dengue fever, West Nile virus or encephalitis.


  1. Agricultural and industrial waste– Waste including animal fecal matter and various chemicals, gasolines and oils can be washed out of farms, factories and other sources as a result of flooding. This waste can contain pesticides or other chemical agents that can cause a variety of adverse health effects


Risk Mitigation: While floodwater increases the chances of the health risks due to exposure to water borne pathogens, vector borne diseases and agricultural or industrial runoff, there are ways to reduce the chances of adverse health effects. The following are ways to protect yourself and others are:


  • Assume any standing water is contaminated until risk determination is performed and declared safe by a public health official. Boil water before drinking or washing, as indicated by local officials.
  • Wash your hands (and children’s hands) with soap and water after coming into contact with floodwater
  • Wear long sleeves, long pants, and insect repellant to reduce the risk of mosquito-borne diseases.
  • Do not let children play in floodwater, or play with toys that have been contaminated with floodwater and have not been disinfected.
  • Avoid exposure to floodwater, especially if you have an open wound. Keep wounds as clean and as dry as possible. Seek medical attention if a wound becomes red, swollen or fills with pus. Double check your vaccination records and update your status, e.g., tetanus, if necessary.


For more information on hazards in floodwater or if you have a potential hazard in your building, location, facility or community and would like us to conduct a risk assessment or assist with risk mitigation, please contact us at