Indoor Mold and Asthma

Science of Fungus

(1) Asthma is estimated to affect 300 million people worldwide and may cause up to 250,000 deaths per year. Many studies and meta-analyses have linked exposure to indoor visible mold or water damage and asthma/wheezing incidence in both children and adults.

Estimates as to the number of homes with mold and moisture damage vary greatly-but are as high as 47% in some studies. Water damaged indoor environments contain a wide range of agents that can cause respiratory problems including molds and their allergens and toxins, bacteria and bacterial endotoxins, viruses, and dust mites and their droppings.

A 2012 meta-analysis of 16 studies reported that indoor visible mold, mold odor, and moisture were significantly associated with greater risk of asthma. Residential Moisture (EE=effect estimate 1.33, 95% CI= confidence interval 1.12-1.56 ), visible mold (EE 1.29, 95% CI 1.04-1.60) and mold odor (EE 1.73, 95% CI 1.19-2.50) were all associated with statistically elevated asthma risk. A recent New Zealand study measured the relationships between housing conditions and presence of new onset wheezing in young children- including 150 wheezing children (median age 32 months) and 300 control children (median age 33 months).

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New onset Wheezing was associated with many medical factors including: Presence of atopy in the child (Odds Ratio= OR 3.25 (95% CI= Confidence interval of 2.03 to 5.22) and family history of atopy (OR 6.97, 95% CI of 2.03-5.22).

New onset wheezing was associated with the following housing factors (partial listing- conditions were assayed by researcher, inspector and parents):

  • Visible mold in bedroom-parent identified 1.80 OR odds ratio risk (95% CI 1.44-2.25)
  • Visible mold in house- parent identified 4.89 OR risk (95% CI 2.15- 11.09)
  • Mold odor in house- parent identified 2.25 OR Risk (95% CI 1.47-3.46)
  • Condensation in house- parent identified 6.65 OR Risk (95% CI 2.01- 22.04)
  • Leaks and water damage- inspector identified 3.56 OR Risk (95% CI 1.46-8.67)

The presence of visible mold and mold odor were associated with a significantly increased risk of wheezing in a dose dependent manner, ie. the risk of asthma became significantly greater within the presence of larger degrees of water damage and mold growth. A child living in a bedroom with the highest degree of mold growth and mold odor had a 14.1 times greater risk of developing wheeze than a child living in a bedroom without visible mold/ mold odor. Controlling mold and moisture in buildings is the best way to control mold growth.

References / Sources:

1. Quansah R JM, Huggt, et al. Residential dampness and molds and the risk of developing asthma: A systematic reveiew an meta-analysis. PLOS ONE. 2012;7(E47526).

2. Caroline Shorter et al,. Indoor visible mold and mold odor are associated with new—onset childhood wheeze in a dose-dependent manner. Indoor Air. 2018 Jan;28(1):6-15. doi: 10.1111/ina.12413. Epub 2017 Sep 11 

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