Flooding from severe weather events will increase the risk of water damage and mold growth in buildings. Mold exposure could play a role in Long COVID and ME, but more research is needed to understand its health impacts.
Key points you should know:
- Almost half of buildings in the U.S. have mold or dampness, which can cause respiratory symptoms and may even trigger diseases like myalgic encephalomyelitis (ME).
- Mold contamination rates are likely to increase in the future due to flooding events linked to climate change.
- People with disabilities are at particularly high risk from mold exposure and flooding events, because they are less likely to have resources to move to a different space or pay for mold remediation.
- Mold could be a component of the “multiple-hit hypothesis,” which suggests that compounded viral, bacterial, and environmental exposures could destabilize the body’s equilibrium and increase the risk of Long COVID and ME.
- Mold exposure is a complicated and little-understood phenomena, with limited and largely untested treatments available. More research is needed to figure out the connection between different species of mold and the health impacts of exposure.
Scott Daniska had been sick with myalgic encephalomyelitis (ME) for years. He was finally beginning to improve when he moved into a freshly painted apartment – which he also realized had mold. The sudden worsening in his symptoms led him to believe he was getting sick from volatile organic compounds (VOCs) commonly found in paint, a known exacerbator of multiple chemical sensitivity.
Multiple chemical sensitivity turns everyday scents, cleaning supplies, and air pollutants into triggers for a wide variety of symptoms. The condition can overlap with ME and may be caused by the same mechanisms as mast cell activation syndrome.
Daniska moved to another building, only to discover that this one contained mold, too. He began experiencing flu-like symptoms. This pushed him to move again, but he struggled to find a space in which his health didn’t decline.
“You can only imagine what kind of hell that was,” Daniska said.
After finding mold contamination at his family home in Connecticut, Daniska finally decided to go to Florida for the winter, living in a tent and going from campsite to campsite to avoid exposures to both mold and VOCs from buildings.
Daniska’s experience is just one of many stories that people with Long COVID and ME have shared about their symptoms worsening — or even beginning — with mold exposure. Long COVID Campaign founder Meighan Stone, for example, posted earlier this year about needing to move and replace many of her belongings due to black mold. Mold and fungi could be a significant component of the “multiple-hit hypothesis,” which suggests that infection-associated chronic conditions can develop after exposure to a series of viral, bacterial, and environmental exposures.
Estimates suggest that nearly half of homes in the U.S. are contaminated by mold. With millions of Americans living with Long COVID and related diseases, the possibility of mold exacerbating someone’s existing illness, or paving the way for it, is high.
With the ongoing threats of climate change — increasing frequency of extreme precipitation events and the growing intensity of hurricanes — the risk of flooding is also going up. That means even more buildings are likely to have water damage in the coming years, and potentially become infiltrated by mold.
“I’m sure it’s getting worse because we’re seeing more extreme weather events,” said Jaime Seltzer, the scientific director at #MEAction. “In the ME community, your case doesn’t have to be kicked off by a particular pathogen, so we also hear stories about people’s illness beginning with a mold exposure. In both [ME and Long COVID] we hear about mold or other fungal pathogens making people feel worse.”
Scientists have long known that exposure to mold can cause respiratory issues, especially in people with asthma and allergies. There are also several rare mold-related illnesses which can cause permanent lung damage. And in the 1990s, several dozen infants near Cleveland developed pulmonary hemorrhages, which was linked to their exposure to the Stachybotrys genus of mold, also known as “black mold.” Ten of the infants died.
But as has been the case with ME and Long COVID, research into the neurological and systemic effects of mold toxicity has been underfunded. “I really feel that environmentally mediated symptoms are a big missing link [for ME],” Daniska said.
I really feel that environmentally mediated symptoms are a big missing link [for ME].
Scott Daniska
Neil Nathan, who practiced medicine for decades and taught at the University of Minnesota for 11 years, began treating patients for mold-related illnesses long before the broader medical world thought to take it seriously as an issue.
“For many people, maybe most, if they identify they’ve been in mold, and they move and get into a safer environment, that’s not enough to cure them,” Nathan said.
And few, it seems, think to ask about the possibility of mold exposure in water-damaged homes.
A complex and dangerous problem
The large scope of mold toxicity makes it challenging to research. When mold grows in damp, water-damaged buildings, it releases several kinds of compounds.
First, like other fungi, mold releases spores to reproduce. Mold spores are tiny; they float and can easily be inhaled. Fragments of spores and mold cells also accumulate in dust at much higher levels, and may be responsible for 70 to 90 percent of inhalation exposure, according to toxicologist Harriet Ammann in the 2016 book, Biology of Microfungi.
Mold also produces mycotoxins, noxious compounds thought to help mold kill off and outcompete other fungi and bacteria. Mycotoxins are even smaller than spores, and have been linked to a slew of dangerous symptoms. And then there are microbial volatile organic compounds (mVOCs), gases emitted by mold that are responsible for the musty, mildew smell. These, too, can have negative impacts on a person’s health.
There are hundreds of indoor fungi species, and a single species can produce more than 90 mycotoxins, mVOCs, and other compounds. All told, that could mean tens of thousands of different compounds are causing health problems. We simply don’t have the research to identify all of them, let alone link each compound to a specific health impact.
In both [ME and Long COVID] we hear about mold or other fungal pathogens making people feel worse.
Jaime Seltzer, scientific director, #MEaction
Ammann wrote about this challenge in her book, noting that individuals may have seemingly unrelated symptoms, which can in fact be traced to different molds.
Multiple case studies have linked mold exposure to illness — though case studies only look at one individual or family and can’t be extrapolated to a broader group. In one case study, a family of five lived in a water-damaged home for five months and all developed symptoms that overlap with ME. Even after finding a mold-free house, the family members continued to be ill for years after their initial exposure.
How mold infiltrates the body and the “multiple-hit hypothesis”
Researchers have slowly uncovered the routes mold compounds can take into our body to cause so many different symptoms. The two we’ve known about for the longest are inhalation, which can cause respiratory symptoms, and ingestion. Eating food that’s contaminated by mycotoxins can cause vomiting, abdominal pain, liver injury, and even cancer.
But now scientists understand that some mold particles are small enough that, after inhalation, they can spread throughout the circulatory system. The nose offers direct access to cranial nerves, giving the compounds a path to the brain and potentially triggering neurological symptoms. Several small studies have found that mold exposure can have neurological consequences on par with mild to moderate traumatic brain injury. One study of mice exposed to mold spores showed memory deficits, inflammation, behavioral changes, and decreased pain thresholds.
Because mold exposure can trigger inflammation and immune dysfunction, Nathan hypothesizes that it could contribute to someone falling ill with ME, or Long COVID. By disrupting the body systemically, mold exposure paves the way for a virus to wreak serious havoc on the body, since the immune system is unable to fight it off, he explained.
This fits with the “multiple-hit hypothesis,” which suggests that many types of exposures could contribute to infection-associated chronic diseases. These “hits” could be previous viral or bacterial infections, exposure to certain chemicals or exposure to mold. In fact, Daniska traces his ME back to a hydrazine exposure, a toxic chemical that was used at his job in a production lab. The cumulative effect of these exposures is like a snowball growing larger as it rolls downhill — ultimately leading to hard-to-treat, complex illnesses.
These hits can come in any order and have unpredictable outcomes.
Mold exposure puts people with preexisting disabilities at more risk
People with disabilities already face a higher level of risk when it comes to natural disasters, and mold is just one more element of that risk. “Extreme weather events cause higher rates of injury and death due to evacuation barriers,” wrote Ryan McGraw, a healthcare community organizer with the Chicago-based organization Access Living, by email. McGraw has seen the ways flooding can initiate “long-term crises in housing stability, transportation access, and the availability of life-sustaining necessities such as medical equipment and caregiving networks,” he explained.
This was precisely the case with Cherlnell Lane, a poetic-storyteller and disabled wheelchair user who has been involved in disability advocacy around Chicago. Lane lives in government-sponsored disability housing that has had repeated water damage incidents. During one of these, the sound of water overhead was so loud that Lane thought it was raining.
“I looked out the window and said, ‘It’s not raining,’” Lane said. It turned out there was a burst pipe, and a torrent of water was pouring from the third floor all the way down to the first. When building management arrived to do repairs, they refused to allow Lane to stay in an unoccupied apartment in the building during construction, even though she had documentation of mold on the walls.
Lane, who has asthma and heart failure, ended up in the hospital multiple times with a cough that made it impossible to speak. While doctors first thought the cough might be related to her heart problems, it ended up being the result of mold, she said. Her symptoms improved while in the hospital, but the cough came back when she returned to her apartment.
So far, Lane hasn’t been able to find any other housing that can meet her needs, and her building management hasn’t remediated the mold.
The cumulative effect of these exposures is like a snowball growing larger as it rolls downhill — ultimately leading to hard-to-treat, complex illnesses.
For those able to afford it, mold remediation can offer a way to avoid relocating after damage. Remediation involves removing mold from buildings, and some specialists are developing more advanced techniques to assist in the process, such as DNA sequencing to identify mold species. But one major challenge is getting rid of mold on fabric and paper materials. That often means getting rid of one’s clothing, blankets, padded furniture, books, and other infected items, which only adds to the expense and difficulty of remediation.
One review identified specific supplements that may help rid the body of toxins, like activated charcoal and chlorophyll, as potential treatment for physicians to consider. Researchers have also found possible benefits from saunas and sweating.
When Seltzer, of #MEAction, moved away from a previous home in a warm, damp environment, she was shocked to see how dramatically some of her symptoms improved. “I believe the environment affects us, but it was only when I experienced that at a personal level that I realized the degree to which it affects people like us,” Seltzer said.
The trouble is, many people can’t easily move, whether it’s because they have friends and family nearby who help with their care, or because they don’t have the money for it, or because they’re living in disability housing, like Lane.
“It can be very challenging,” Seltzer said. “It’s much easier said than done.”
Lorraine Boissoneault is a science and history writer based in Chicago. Her book Body Weather: Notes on Chronic Illness in the Anthropocene looks at the links between illness, the environment, and severe weather. You can follow her on Bluesky, Substack, and Instagram.
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