Visible Mould and Odour Is Related to Childhood Asthma
Asthma is a very common chronic respiratory disease that narrows the airways and causes breathing difficulty. A good deal of research evidence is increasing in the literature linking indoor dampness and mould with the development of asthma.
Although many of the underlying mechanisms remain unknown, countries such as Australia and New Zealand have high rates of both asthma and indoor mould. This blog post reviews a recent paper from the literature that examined the association between childhood wheeze and the presence of indoor visible mould and mould odour.
In this experiment 150 children who were diagnosed with new onset wheeze and were aged between 1 and 7 years were each matched with two children that did not have any history of wheeze. Each child’s home was then assessed for the following factors: (i) presence of moisture damage, (ii) presence of condensation, and (iii) mould growth.
Three types of assessors were used to investigate these factors and included (i) an independent building assessor, (ii) the parents own first person account and then (iii) the academic researchers themselves who also visited each property.
The following tests were performed inside each dwelling and included measurement of temperature, humidity, and collection of airborne microbes using cloth wipes. Children were also skin pricked to determine that they were in fact allergic. The results showed a very strong positive association between observations of visible mould and new onset wheezing in children which was a dose dependent correlation. Interestingly, measurement of microbial levels using qPCR was not associated with identification of children having new onset wheezing.
The practical implications of this study mean that actually seeing dampness and mould is the best indicator of an increased likelihood of conditions conducive to new onset wheezing whereas measuring temperature or humidity and even surrogate microbial sampling with dust cloths were not good indicators.
These studies show us with evidence that indoor dampness and mould is strongly associated with the development of asthma and indeed it is those fungal fragments, spores, cell wall components, volatile organic compounds, and secondary microbial metabolites such as mycotoxins that are normally present inside buildings showing signs of visible mould that are thought to cause the wheeze.
This study is particularly important because three different types of people were used to make the assessments. By including the parents as well as an independent building inspector along with the scientists it is possible to examine the correlation between their interpretations of dampness and presence of mould with the epidemiological results of allergy and asthma which occurred versus the control group of children.
The scientists designed a simple scale for mould between zero and three which categorised visible mould for each room in the home as either none, small, moderate or large. Similarly, mould odour in bedrooms was categorised on a 0 to 3 scale of none, mild, moderate and severe. Because mould odour is a subjective experience, the scientists trained both the building inspector and the other assessors using Petri plates on which Cladosporium, Alternaria, Aspergillus and Penicillium had been grown. This olfactory pretraining highlighted typical odours found in water damaged buildings.
Interestingly visible mould was most frequently detected by parents and the scientists whereas the building inspectors often missed mould that was detected by either of the other groups. One might interpret these results by saying that either parents are more vigilant or potentially over-report the presence of mould – however this connection was not observed for the scientists. In their conclusion to this research the academics wrote that while researcher/scientist and parental prevalence of observed mould was similar, the building inspector observed mould-prevalence was much lower. One of the recommendations of this research was that building inspectors require appropriate training in the identification of mould inside buildings which they may not be trained to detect and therefore may under-report this in their findings.
Another interesting finding of this study was that the researchers made sure to examine every room of the home and at minimum chose at least seven locations within the building using the scoring system between zero and three meant that across the seven rooms a home could be rated up to a total score of 21. In order to assess the accuracy of the building inspector that individual was blinded to the status of the child’s wheeze status at the time of each inspection in order not to bias the observations. The building inspector in many cases took repeated moisture measurements using a prong based moisture sensor. Despite the apparent objectivity moisture measurements were not found to be correlated with identification of building specific factors that could be connected with new onset wheeze in children.
Another interesting conclusion of this study was that no association was found between temperature, relative humidity, absolute humidity, due point, or building moisture and new onset wheezing in children and that the visible presence of mould itself was the most important factor in eliciting new onset wheezing in children.
The researchers conclude their paper by highlighting the fact that worldwide the prevalence of indoor mould is thought to occur in 5 to 10% of homes in cold climates and in as much as 10 to 30% of houses in temperate or warm climates.
If you are at all concerned about mould and mould odour whether it is visible or not you should have your home professionally tested. There are different ways to do this which are cost-effective and efficient. Obviously on-site inspections involve attendance by building experts but in many cases a simple visual inspection of the home may reveal hotspots (regions of interest) where moisture may be accumulating that is directly related to mould growth. For example, this research paper highlighted that the majority of visible mould found in children’s bedrooms was detected on or around windows followed by curtains followed by walls and then ceilings and to a much lesser extent on bedding, wardrobes or other areas. When in doubt, have your home professionally tested and beware of building inspectors who may underestimate what is quite obvious to others!
Source: Indoor visible mold and mold odor are associated with new-onset childhood wheeze in a dose-dependent manner. Shorter C, Crane J, Pierse N, Barnes P, Kang J, Wickens K, Douwes J, Stanley T, Täubel M, Hyvärinen A, Howden-Chapman P; Wellington Region General Practitioner Research Network. Indoor Air. 2018 Jan;28(1):6-15. doi: 10.1111/ina.12413,