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Heavy rains and sea level rise contribute to major flooding events that are one effect of climate change. Surging water rushing into buildings often causes immediate harms, such as drowning deaths, injuries sustained while seeking shelter or fleeing, and hypothermia after exposure to cold waters with no shelter or heat.

But long after news trucks leave and public attention moves on, flooding continues to affect communities in visible and less visible ways. Among the less visible threats is a higher risk of respiratory health problems like asthma and allergic reactions. Fortunately, you can take steps to minimize or avoid flooding, or to reduce respiratory health risks after flooding occurs.

How does flooding trigger respiratory health issues?

Flooding may bring water contaminated with toxic chemicals, heavy metals, pesticides, biotoxins, sewage, and water-borne pathogens into buildings. Afterward, some toxic contaminants remain in dried sediments left behind. When disturbed through everyday actions like walking and cleaning, this turns into microscopic airborne dust. Anything in that dried flood sediment — the toxic chemicals, the metals, the biotoxins — is now in the air you breathe into your lungs, potentially affecting your respiratory health.

Buildings needn’t be submerged during flooding to spur respiratory problems. Many homes we studied after Hurricane Ida suffered water intrusion through roofs, windows, and ventilation ducts — and some were more than 100 miles away from coastal regions that bore the brunt of the storm.

The growth of mold can also affect health

Another common hazard is mold, a fungal growth that forms and spreads on damp or decaying organic matter. Indoor mold generally grows due to extensive dampness, and signals a problem with water or moisture. Damp materials inside buildings following a flood create perfect conditions for rapid mold growth.

Mold can be found indoors and outdoors in all climates. It spreads by making tiny spores that float through the air to land in other locations. No indoor space is entirely free from mold spores, but exposure to high concentrations is linked with respiratory complications such as asthma, allergic rhinitis, and sinusitis. Thus, flooding affects respiratory health by increasing the risk of exposure to higher concentrations of mold spores outdoors and indoors.

For example, after Hurricane Katrina in New Orleans in 2005, the average outdoor concentration of mold spores in flooded areas was roughly double that of non-flooded areas, and the highest concentrations of mold spores were measured indoors. A study on the aftermath of Hurricane Katrina and the flooding in the UK in 2007 showed that water damage accelerated mold growth and respiratory allergies.

Children are especially vulnerable to health problems triggered by mold. All respiratory symptoms — including asthma, bronchitis, eye irritation, and cough — occurred more often in homes reporting mold or dampness, according to a study on the respiratory health of young children in 30 Canadian communities. Other research demonstrates that mold contributes to development of asthma in children.

What can you do to protect against the health harms of flooding?

Our research in New Orleans, LA after Hurricane Ida in 2021 identified common factors — both in housing and flooding events — with great impact on respiratory health. Preliminary results suggest two deciding factors in whether substantial indoor mold appeared were the age of a building’s roof and how many precautionary measures people took after flooding from the hurricane. The impact on respiratory health also varied with flood water height, days per week spent at home, and how many precautionary measures were taken after Ida swept through.

Informed by this and other research, we offer the following tips — some to tackle before flooding or heavy rains, and some to take afterward. While you may not be able to entirely prevent flooding from hurricanes or major storms, taking these and other steps can help.

Before seasonal storms, flooding, or heavy rains start: Protect against water intrusion

• Repair the roof, clean gutters, and seal around skylights, vent pipes, and chimneys to prevent leaks. These are some of the most vulnerable components of a building during storms and hurricanes.
• Declutter drains and empty septic tanks.
• Construct barriers and seal cracks in outer walls and around windows, to prevent heavy rain and floodwater from entering.
• Install a sump pump to drain water from the basement, and backflow valves on sewer lines to prevent water from backing up into the home.

After flooding or major rainstorms: Move quickly to reduce dampness and mold growth

The Environmental Protection Agency recommends limiting contact with flood water, which may have electrical hazards and hazardous substances, including raw sewage. Additionally:

• Minimize your stay in flooded regions (particularly after hurricanes) or buildings until they are dry and safe.
• Check building for traces of water intrusion, dampness, and mold growth immediately after flooding.
• Drain floodwater and dispose of remaining sediment.
• Remove affected porous materials. If possible, dry them outdoors under sunlight.
• Increase the ventilation rate by leaving all windows and doors open, or use a large exhaust fan to dry out the building as fast as possible.
• Use dehumidifiers in damp spaces such as basements.
• Upgrade the air filters in your HVAC system to at least MERV 13, or use portable air cleaners with HEPA filters to reduce your exposure to airborne mold spores.

What to do if you spot mold growth

• Wear a well-fitted N95 face mask, gloves, and rubber boots to clean.
• Clean and disinfect anything that has been in contact with water using soap, detergents, and/or antibacterial cleaning products.
• Dispose of moldy materials in sealed heavy-duty plastic bags.

Taking steps like these — before and after a major storm — goes a long way toward protecting your respiratory health.

Read Flooding Brings Deep Trouble in Harvard Medicine magazine to learn more about the health hazards related to floods.

About the Authors

Parham Azimi, PhD, Contributor

Dr. Parham Azimi is a research associate in the department of environmental health at the Harvard T.H. Chan School of Public Health, investigating the indoor environment’s impact on occupant health and wellness and strategies to improve … See Full Bio View all posts by Parham Azimi, PhD

Joseph Allen, DSc, MPH, CIH, Contributor

Dr. Joseph Allen is an associate professor in the department of environmental health at the Harvard T.H. Chan School of Public Health, and the director of Harvard’s Healthy Buildings Program. He is the coauthor of Healthy … See Full Bio View all posts by Joseph Allen, DSc, MPH, CIH

Ready to address excessive drinking in your life? Many people find peer support helps them take steps toward recovery. Two well-known self-help organizations built around peer support are Alcoholics Anonymous (AA) and Self-Management and Recovery Training (SMART Recovery). While some people seeking recovery even attend both programs, others forego both options.

Why do people choose those different paths — and what do they like, dislike, and find helpful about their chosen option? To find out, researchers questioned 80 participants enrolled in a two-year study about recovery from alcohol use disorder (20 each in AA, SMART Recovery, both, or neither).

Dr. John F. Kelly, professor of psychiatry in addiction medicine at Harvard Medical School, led the study, which was published in the Journal of Substance Use and Addiction Treatment. Here he explains key findings and shares his perspective and advice for people seeking peer support to stop problematic drinking.

Camaraderie: A common theme for both groups

The most striking finding was that for people attending either group, camaraderie was by far the most important aspect.

“There’s something about the connection with other people with similar experiences that helps decrease the self-stigma and shame that people have around this issue,” says Dr. Kelly, who founded the Recovery Research Institute at Massachusetts General Hospital. “Seeing role models of people who found solutions and a way out, and championing these examples of successful recovery, is very powerful,” he adds.

What else do people appreciate about AA?

Founded in 1935, AA has been around far longer than SMART Recovery, which began in 1990. AA’s popularity makes it easy to find meetings, which was one benefit cited in the study. “Within a 45-minute drive of downtown Boston, there are 1,800 AA meetings a week, compared with just 30 SMART meetings,” says Dr. Kelly.

You can also find a wider variety of specialized AA meetings, including those catering to different age groups, women, or LGBTQ+ people, for example. Larger metropolitan areas may have meetings conducted in different languages, as well.

AA follows a 12-step program, defined as a set of spiritual principles that help people achieve sobriety. Yet hardly anyone in the study mentioned spirituality in their responses, says Dr. Kelly. In fact, other research suggests that about half the people attending AA don’t seem to have a strong sense of needing to believe in a formal deity or higher power. “Some people say that connection with other people is what makes it a spiritual experience,” he says.

What else draws people to SMART Recovery?

The study results confirm years of anecdotal reports about why people choose SMART Recovery over AA, says Dr. Kelly. “What attracts people to SMART Recovery is the organization’s focus on science and clinical evidence,” he says.

Their approach incorporates cognitive behavioral therapy (CBT) and motivational psychology into their support groups. The goal is to help participants to recognize and cope with the emotional and environmental triggers for their drinking. Still, in this study, people who chose SMART Recovery stayed with it for the social aspects, according to responses about what they like best about the program, says Dr. Kelly.

Compared to people who attended AA, study participants who chose SMART tended to have less severe problems with alcohol use. They had more education, higher rates of employment, and greater economic resources. They were also less likely to have had prior treatment or involvement with the criminal justice system. SMART may be a particularly good fit for people with that kind of profile.

People who attended both AA and SMART Recovery groups tended to be the most severely affected by their problems with alcohol, and were seeking anything and everything to get help. Those who attended neither program were less seriously affected.

What are other differences between AA and SMART Recovery?

While AA groups are led by members in recovery, SMART groups are led by trained facilitators who are not required to be in recovery themselves.

In the study, that lack of “lived experience” wasn’t perceived as a negative, although some people mentioned that they didn’t like some of the facilitators, Dr. Kelly says. However, a trained facilitator can gently stop and redirect members who engage in meandering, lengthy, and potentially irritating monologues (known as a “drunkalogue”) that may dominate group discussions. AA group leaders don’t intervene in that way and have no formal group facilitation training.

However, AA strongly encourages people who join the fellowship, as it is called, to have a sponsor. Sponsors are experienced members with at least one year of recovery who serve as mentors for new members and are available between meetings. SMART Recovery doesn’t have formal sponsors, but facilitators encourage people to swap phone numbers and reach out to each other between meetings.

Should you participate in a support group to stop drinking?

“When I’m counseling patients, I lay out the different options and let people decide which program seems like the best personal fit for them,” says Dr. Kelly.

Because AA has been around for much longer, he notes that there’s more evidence about what contributes most to success with this approach. Research shows the three factors that have the biggest positive effect on remission for alcohol misuse are:

• Having a sponsor. This is the single most important factor influencing recovery.
• Attending at least three meetings per week. Consistently showing up, especially during the first year, also appears to boost the odds of recovery.
• Speaking at meetings. Saying something aloud in the group meetings — even if it’s just a sentence or two — reinforces the likelihood of ongoing recovery. It also makes it easier to connect with other members in the “meeting after the meeting.”

About the Author

Julie Corliss, Executive Editor, Harvard Heart Letter

Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss

About the Reviewer

Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing

Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD