SEATTLE—Exposure to mold, whether indoors or outdoors, seems to play a part in the development or worsening of respiratory problems, including asthma. Although researchers generally agree that mold affects respiratory health, they are uncertain if it is the mold itself that causes symptoms or the dust mites that flourish in damp environments. Furthermore, if mold is the culprit, exactly how does it affect the lungs?

A symposium at the 2003 annual conference of the American Thoracic Society in Seattle featured researchers from Europe and the United States. They presented their findings on the respiratory effects of mold in children and adults and the effects of outdoor fungal spores on asthma.[1]

Bert Brunekreef, PhD, a Professor of Environmental Epidemiology at Utrecht University in the Netherlands, posed the question, “What is a damp space?” It can involve visible water, water damage, damp spots, leaks, flooding, and/or mold. The effects of dampness and mold are hard to study, Dr. Brunekreef noted, because of the broad definition of dampness and the wide range of health problems related to dampness (eg, dust mites, bacteria from rotting wood or other materials, allergens, endotoxins, and mycotoxins).

“The effects of mold can be of various types also,” said Dr. Brunekreef, “including respiratory symptoms; lung function changes; specific and nonspecific bronchial hyperresponsiveness; sensitization to molds, mites, and other allergens; airway inflammation; and nonspecific symptoms like nausea and headaches.”

Rylander et al[2] studied two schools in Sweden—one that had a documented mold problem and one that had no mold problem—to measure the effect of mold on airway inflammation and atopy in schoolchildren in the first to fifth grades. Atopy was assessed using a skin test, and levels of airborne (1->3)-ß-d-glucan (a component of the mold cell wall) were measured in several classrooms in both schools.

The amount of (1->3)-ß-d-glucan in the control school averaged 2.9 ng/m3, while in the problem school it averaged 15.3 ng/m3. Approximately 20% of the children in both schools had an atopic reaction against one or more allergens. Interestingly, though, only one of the 206 children in the study had a positive skin test reaction against mold.

The incidence of respiratory symptoms was higher in the problem school than the control school regardless of children’s atopic status. However, atopic children in the problem school had more respiratory symptoms—specifically, cough with or without phlegm, dry cough at night, or hoarseness—than did either the atopic children in the control school or the nonatopic children in the problem school.

During the summer, the extent of symptoms decreased and was similar among children from both schools. However, after the start of the school year, nasal symptoms increased rapidly in children attending the problem school but remained the same for children in the control school.

Rylander et al admitted that it was not possible to determine whether (1->3)-ß-d-glucan was the causative agent for the mold-exposure–related effects, but they noted that the cell-wall component is biologically potent in low doses and remains suspect.[2]

A population-based cross-sectional study from Finland studied respiratory health and the occurrence of water damage in the homes of 2,568 children ages 1 to 6. A dose-response relationship was observed between mold odor and water damage in the past year and respiratory symptoms.[3]

Dampness seems to be associated with poor ventilation, observed Dr. Brunekreef. “Where there is little ventilation, there are perhaps more dampness problems, more accumulation of relevant substances, and the association [between mold and respiratory symptoms] becomes more clearly visible.”

In both the home and the workplace, “indoor mold and dampness problems have been reported to be common all around the world,” said Maritta S. Jaakkola, MD, a researcher at the Finnish Institute of Occupational Health in Helsinki.

Dr. Jaakkola agreed with Dr. Brunekreef that there seems to be a dose-response relationship between mold and asthma. However, she added, “We don’t know the mechanisms by which indoor molds cause asthma and respiratory diseases.”

The European Community Respiratory Health Survey was an international 38-center study on adult asthma that assessed participants’ exposure to dampness, mold, and house dust mites, and also measured levels of allergic sensitization, asthma, and bronchial hyperresponsiveness.[4] One fifth of the 18,873 persons included in the study were sensitized to house dust mite. Overall, about 5.9% of the study population had a positive skin response to either Alternaria alternatum or Cladosporium herbarum, two common species of mold.

Water damage and mold in the home were both related to asthma symptoms and bronchial responsiveness. The investigators noted that it is often difficult to attribute asthma to mold sensitization or exposure because people who are sensitized to mold are often sensitized to other inhaled allergens. However, this study showed that those who were sensitized to either of two common molds had more asthma symptoms in the presence of mold than did other persons.

“We speculate that the relationships between indoor mold exposure and current asthma are caused by a combination of allergic and nonallergic mold-related effects, leading both to new-onset asthma and aggravation of asthma,” the authors wrote.[4]

One criticism of studies in which dampness in the home is self-reported is that there may be a tendency for patients to overreport damp conditions. A case-control study by Williamson et al[5] used independent assessment of homes along with spirometry and questionnaires. They found that both asthma patients and controls tended to underreport dampness. In this study, a significant association was found between severity of asthma and total dampness and total mold scores. The greater the dampness or mold in the home, the greater the severity of asthma.

If indoor mold has been implicated in respiratory problems, what about outdoor fungal spores? Ralph J. Delfino, MD, PhD, an Associate Clinical Professor of Medicine at the University of California, Irvine, addressed this question.

In 1997, Dr. Delfino and colleagues conducted a study measuring the day-to-day changes in asthma severity in 22 patients for eight weeks.[6] During the study, daily outdoor concentrations of fungi, pollen, and particulate matter were measured. After controlling for variations in the weather, total fungal spore concentrations were associated with all outcomes: When spore concentrations were high, so were asthma symptom scores and inhaler use. Evening peak expiratory flow rates decreased as spore counts increased.

This study suggests that outdoor fungal spore concentrations can affect the daily respiratory status of patients with asthma. In fact, Dr. Delfino was involved in several similarly designed studies, all of which found an association between outdoor mold spores and asthma symptoms.

“It appears that outdoor fungal spores are associated with acute asthma,” said Dr. Delfino. “A variety of spore types appear to be driving these associations, and they may be independent of each other.”

Prognostic studies and interventional trials are needed, said Dr. Jaakkola. Several questions remain unanswered: What mold species are relevant for health effects? What is the mechanism by which molds induce asthma and respiratory symptoms? Is there synergism between mold and other indoor environmental exposures?

“There is strong evidence that indoor molds at home increase the risk of wheezing and respiratory symptoms and asthma,” Dr. Jaakkola said. “There is also increasing evidence that molds in the workplace increase the risk of wheezing and [other] symptoms. And, there is evidence that indoor mold increases the severity of already established underlying disease and that repair of the mold problems alleviates asthma symptoms.”

—Gale Jurasek

References
1. Jaakkola MS, Williams D, moderators. Respiratory health effects of molds. Presented at: annual conference of the American Thoracic Society; May 19, 2003; Seattle, Wash.
2. Rylander R, Norrhall M, Engdahl U, et al. Airways inflammation, atopy, and (1Æ3)-ß-d-glucan exposures in two schools. Am J Respir Crit Care Med. 1998;158:1685-1687.
3. Jaakkola JJ, Jaakkola M, Ruotsalainen R. Home dampness and molds as determinants of respiratory symptoms and asthma in pre-school children. J Expo Anal Environ Epidemiol. 1993;3:129-142.
4. Zock J-P, Jarvis D, Luczynska C, et al. Housing characteristics, reported mold exposure, and asthma in the European Community Respiratory Health Survey. J Allergy Clin Immunol. 2002;110:285-292.
5. Williamson IJ, Martin CJ, McGill G, et al. Damp housing and asthma: a case-control study. Thorax. 1997;52:229-234.
6. Delfino RJ, Zeiger RS, Seltzer JM, et al. The effect of outdoor fungal spore concentrations on daily asthma severity. Environ Health Perspect. 1997; 105:622-635.

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