Dampness, Mold and Water-Damaged Buildings

Mold Growing on a Wall

When I used to live in Seattle, I was trained by the American Lung Association in a special program to do home inspections. The focus was to help individuals understand if they had indoor air quality problems. While we covered a lot of issues that affect air quality, we also touched on water damage and mold. Mold growth in homes often occurs due to elevated humidity or water leaks that cause building materials to stay damp, allowing for mold growth. During the training course, they told us to trust our nose: if we could smell a problem, there likely was a problem. 

Water-damaged buildings, where mold growth occurs, are common. And studies show that after being water damaged, air within the damaged buildings contains heightened levels of fungi (mold), mycotoxins (fungal toxins), bacteria, bacterial toxins, allergens and other volatile compounds produced by the bacterial and mold growth present (Hope 2013).

Estimates suggest that in colder climates, between 5% and 30% of homes have a problem from water damage or dampness, while in warmer climates, between 10% and 60% have potential concerns (Quansah 2012). Estimates for the United States suggest that approximately 47% of homes have water dampness and mold problems (Park 2022). For commercial buildings, estimates suggest that 85% have water damage with 45% currently having a water leak (Park 2022).

Water-Damaged Buildings and Symptoms   

The strongest evidence of health conditions caused by water-damaged and damp buildings are for respiratory symptoms. Asthma rates are 1.5 times higher for individuals exposed to indoor dampness and mold as compared to unexposed individuals (Quansah 2012).

Rhinitis, a condition that includes a runny or stuffy nose, can also be caused by exposure to allergens. Living or working in damp or moldy buildings increases the risks for rhinitis symptoms between 1.5 and 2.2 times (Jaakkola 2013). Data from exposure to dampness and mold in schools also suggests increased risks for coughing and wheezing in exposed children (Fisk 2019).

Studies on children exposed to indoor mold show significant reductions in IQ (Jedrychowski 2011). Rates of depression are also higher in those exposed to damp living environments and mold (Shenassa 2007). Mold exposure has even been reported to cause or contribute to chronic pain, dementia, balance problems and loss of coordination (Empting 2009).

How Mold Affects Health

The mechanisms that cause health problems in water-damaged buildings include heightened exposure levels to mycotoxins. In damp buildings, excess mold growth causes the release of mycotoxins into the environment (Straus 2006, Richard 1999). These mycotoxins can be inhaled, swallowed or even absorbed through the skin (Hooper 2009, Brasel 2004, Boonen 2012). 

Mycotoxins are known to disrupt health in a number of ways. They can be both allergenic and directly toxic. Some mycotoxins are known to suppress immune function, which can cause building occupants to be more susceptible to infections (Reijula 2003). Other mycotoxins are liver and kidney toxic or carcinogenic, potentially increasing cancer risks or disrupting liver and kidney function (Engelhart 2002). Research also shows that mycotoxins are neurotoxic: they can damage the brain and nervous system (Doi 2011).

With any significant mold exposure, there is also a possibility for a direct fungal infection. 


Flooding Is a Common Cause of Water Damage to Buildings

Some of the strongest associations with health effects, outlined above, are from buildings that have a moldy smell. In cases where there is visible mold, water staining, or a mold-type odor, it is important to fix the mold and dampness problems. First and foremost, sources of water, from plumbing, leaks and condensation that allow for mold growth, have to be eliminated. The Environmental Protection Agency has some good resources outlining approaches to clean up water damage and mold. However, attempting to clean up a serious mold problem can also cause a much larger exposure if done improperly. This can be especially relevant in someone who has had ongoing exposure or who is displaying potential symptoms. 

In general, porous items, like carpet, wallboard or ceiling tile that gets contaminated should be removed and thrown away. For porous materials, no treatment has been shown to be effective at completely removing mold (Peitzsch 2012). Mold should not be painted or caulked over. If humidity levels are too high, generally over 60%, measures to lower humidity, like increased ventilation or dehumidification should be utilized. Mold growth readily occurs on building materials once humidity is greater than 75% (Johansson 2012).


In those exposed to damp buildings and mold, there is the question of how best to treat the exposure. First, and most obvious, continuing exposure to mycotoxins needs to be eliminated. Remediation needs to take place to correct the source of the exposure. In many mild to moderate cases, this may be enough to significantly improve symptoms. 

While beyond the full scope of this article, antioxidants, dietary measures, sauna, and compounds that sequester mycotoxins in the digestive tract all appear to have their place in the treatment of more severe cases of exposure (Hope 2013). These treatments can help in removing mycotoxins from the body, which may also help to reduce the symptoms associated with long-term exposure.


Both residential and commercial buildings are often water damaged and can easily develop a mold problem. Considering the concerns around mycotoxins, identifying problems and addressing water-damaged buildings appropriately can be an important component in maintaining and supporting health. In cases of more significant exposures, seeking a knowledgeable health-care provider may also be helpful for assessing symptoms and providing appropriate treatment. 

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