Dampness-Related Health Risks
Indoor dampness or mold in homes, determined visually or via mold odor, is associated with increases in asthma exacerbation, cough, wheeze, upper respiratory symptoms, asthma development, shortness of breath, ever diagnosed asthma, respiratory infections, bronchitis, allergic rhinitis, and eczema. Meta-analyses of published literature often indicate 30% to 70% increases in the prevalence rates of these adverse health effects in homes with dampness and mold. High indoor humidity in homes increases the number of house dust mites present and the allergen from these mites is associated with increases in asthma and respiratory health effects. Dampness and mold in work places and schools are also associated with increased respiratory health effects. The specific agents, e.g., molds, bacteria, or organic chemicals, causing the health effects of dampness and mold are uncertain.
Based on multiple critical reviews and meta analyses of a large body of research, indoor dampness or mold, determined visually or via mold odor, is associated with increases in asthma exacerbation, cough, wheeze, upper respiratory symptoms, asthma development, shortness of breath, ever diagnosed asthma, respiratory infections, bronchitis, allergic rhinitis, and eczema. The odds ratios resulting from meta-analyses often indicate 30% to 70% increases in the prevalence rates of health effects in homes with dampness and mold. The specific agents, e.g., molds, bacteria, or organic chemicals, causing these health effects are uncertain and insufficient scientific data are available to draw conclusions about the association of dampness and mold with several other health effects. Overall, research indicates that building dampness and mold represents a significant public health problem and that steps should be taken to reduce building dampness and mold.
Based on 16 studies published in 18 papers, visible dampness and mold or mold odor in workplaces is also associated with increases in adverse respiratory health effects, particularly respiratory health effects associated with asthma. Damp microbially contaminated sections of heating, ventilating, and air condition systems may contribute to these health effects.
The relatively consistent findings of a substantial number of quality studies indicate that there is an association of dampness and mold in schools with increased respiratory health symptoms, such as cough or wheeze, among occupants of the schools. Visible dampness and mold or mold odor are more clearly associated with symptoms than are higher levels of measured mold in air or dust. Objective health measures are, however, less consistently associated with dampness and mold in schools.
Research has clearly demonstrated that dust mite allergen increases the risk of various health effects. Nearly all of this research has been performed in houses. Where concentrations of mite allergen in house dust are greater than approximately 2 micrograms allergen per gram of dust, susceptible people have a much higher risk of becoming sensitized to (i.e., have an allergic response to) dust mite allergen. Those who are sensitized to dust mite allergen have a several-fold increased risk of asthma. Mite allergens exacerbate allergic rhinitis (inflammation of the nasal tissues due to allergen exposures causing sneezing, runny nose, postnasal drip, and congestion) and atopic dermatitis (allergen-caused inflammation of the skin resulting in rash and itching). A National Academy of Science committee concluded that the evidence was sufficient to conclude that dust mite allergen caused development of the disease of asthma and caused exacerbation of asthma in those with asthma. Unfortunately, control of indoor dust mites has proven difficult. At the present time, the health benefits of humidity reduction interventions designed to reduce indoor dust mites are not well documented.
Some molds can produce highly toxic chemicals called mycotoxins under some growth conditions. Some bacteria can also produce toxic chemicals. The potential health effects of mycotoxins have been reviewed by a committee of the National Academy of Sciences, Institute of Medicine. Studies with exposures of living cells and animals to mycotoxins indicate that some mycotoxins are very potent, i.e., only very small amounts of some mycotoxins can produce substantial effects in cells or animals. However, it is not known whether the indoor air concentrations of mycotoxins caused by microbial growth in damp buildings can become high enough to cause health effects.
The health risk of the increases in microbial and non-microbial indoor gas-phase chemical chemicals in indoor air from building dampness are not well understood.
The estimated annual health related costs of dampness and mold in the U.S. are as high as $17 billion for asthma morbidity and mortality, $3.7 billion for allergic rhinitis, and $1.9 billion for acute bronchitis.