Flooding and Respiratory Health: Long-Term Impacts

Heavy rains and sea level rise drive major flooding events that cause immediate harms—drowning deaths, injuries while seeking shelter or fleeing, and hypothermia from cold water exposure. But long after floodwaters recede, communities face less visible threats, including higher risks of respiratory problems like asthma and allergic reactions.

How Flooding Affects Indoor Air Quality

Contaminated Sediments

Floodwaters can carry toxic chemicals, heavy metals, pesticides, biotoxins, sewage, and pathogens into buildings. After water dries, these contaminants remain in sediments. Everyday activities like walking or cleaning stir the dried sediments into fine dust, making toxic particles airborne and posing inhalation hazards.

Water Intrusion Without Submersion

Buildings need not be fully submerged to suffer respiratory risks. After Hurricane Ida, many homes more than 100 miles inland had water intrusion through roofs, windows, and vents—enough to introduce contaminants and moisture.

Mold Growth

  • Mold thrives on damp or decaying organic matter and spreads via airborne spores.
  • Indoor mold concentrations rise sharply after floods, increasing risks of asthma, allergic rhinitis, and sinusitis.
  • Outdoor mold spore counts also double in flooded areas, as seen after Hurricane Katrina.

Evidence from Research

Studies in New Orleans and the U.K. after major floods showed accelerated mold growth and higher rates of respiratory allergies. A Canadian study of young children in 30 communities found that homes reporting mold or dampness had more asthma, bronchitis, eye irritation, and cough. Research after Hurricane Ida identified two key factors in indoor mold development: the age of a building’s roof and the number of precautionary measures taken post-flooding. Respiratory impacts also varied with floodwater height, days spent at home, and mitigation steps taken.

Precautions to Protect Respiratory Health

  • Limit contact with flood water, which may contain electrical hazards and raw sewage.

While you cannot entirely prevent flooding from major storms, taking these steps before and after an event helps protect your respiratory health.

For more on flood-related health hazards, read “Flooding Brings Deep Trouble” in Harvard Medicine magazine.