In a recent news story extensive mold infestation was found in a house that had oriented strand boards (OSB) instead of plywood walls. The house also was tightly sealed trapping moisture, which contributed to the extensive mold problem.
Mold problems have been around for centuries, but only in the past few decades allergists have pointed out to their patients how important it is to prevent this from happening.
In the following I will review a few typical scenarios that can lead to mold accumulation.
1. Mold from airtight house construction
The homeowner described in the link above is not the only case in the world that has a mold problem. Energy efficient homes are popular because they save energy costs; homeowners often also respond to gas companies, electric utility companies and government incentives to convert to airtight home construction.
In the 1980’s the construction industry introduced the cheaper OSB products to replace the more expensive plywood for wall construction. This is often the problem with newer house construction. However, older homes are not immune to mold development.
2. Roof leaks in older homes
Older homes that were built in the 1970’s may have plywood walls and have a bit of airflow from poorer wall construction, which would prevent mold formation. But roofs are older and do not always get replaced right away when a leak is detected. It may even take some time in areas where there is less precipitation before it is picked up during a particularly heavy rainstorm. Water that enters from a leaky roof can form a puddle on top of the ceiling where mold softens the drywall material until a leak in the ceiling causes water to drip down onto the floor. The mold spores multiply particularly well in wall-to-wall carpeting, but OSB material is also a good growth opportunity for molds due to the mini air spaces between the glued wood pieces. Plywood with its several tight layers is much more resistant to water penetration and mold growth.
3. Mold growth after hurricanes
After hurricane Sandy images of “black mold” were frequently shown in the media. The problem is that after 48 hours anything that was in contact with water produces mold. However, often with disasters like hurricanes there are evacuation orders and you cannot return to your home for several days. There may be further delay because there is a waiting period for insurers to assess the amount of damage, before you can clean all surfaces affected by mold.
The end is result often that expensive mold sanitation is needed or the person ends up moving away and the house is levelled before a new house can be built.
4. Effects of molds
People with preexisting allergies and asthma are more susceptible to the effects of molds. It leads to itchy eyes, wheezing, coughing, and exacerbation of asthma.
Here is a brief overview what the CDC is stating about mold. This site also explains that you can recognize a mold problem because of a musty smell or foul stench in the air and because of the appearance (discoloration of ceilings or walls, water damage).
You can clean hard surfaces with bleach water. Bleach kills molds, but it may have to be cleaned several times within a few days to get rid of the last spores. Whatever cannot be sanitized in this way must be removed or replaced.
5. Health concerns regarding molds
Ref. 1 reviewed the public concern about the toxic effects of molds. It noted that with the Internet and the popular press having exaggerated some of the connections of symptoms with mold allergies, the term “mold madness” has been coined (Ref.2). Despite the paranoia in the general public about toxins from molds, there is only a small percentage of the population that is sensitive to molds where IgE antibodies and IgG antibodies against molds can be determined through blood tests. These individuals often are also allergic to other environmental allergens like grass pollen and dust mites. The asthmatic reactions in sensitive people are not as severe as what peanut traces would do to peanut sensitive patients, but skin testing and blood test screening for specific IgE and IgG antibodies do often confirm that sensitive people indeed can have specific mold allergies. In the vast majority of people these tests are negative and correlations between mold infestations and allergic reactions could not be verified (Ref.1).
6. Fixing mold damage and dealing with allergies
It follows from this that you should remove any visible molds and fix whatever the cause was for its appearance. Carefully disinfect the areas with diluted bleach water (the CDC recommends 1 cup of bleach per 1 gallon of water) several times. Make sure the areas are dry and not musty otherwise you have work on improving ventilation. If you are not one of these hypersensitive persons, there is nothing to worry further. However, if you are hypersensitive an allergist should examine you. Common indoor molds that cause the so-called “immediate type hyper reactivity” are due to the mold species Aspergillum and Penicillium. Most outdoor molds that can cause problems for sensitive people are due to Alternaria and Cladosporium species. The latter would be the ones found in carpets after a leaky roof has caused problems. When the allergist has found specific allergies to one or several of the mold species, allergy shots may be prescribed that would have to be given weekly to the sensitive person who was found to have environmentally induced asthma. Often it takes several years for these desensitization shots to stop the affected person from reacting to molds. In some cases patients need to stay on these shots life-long.
The key with regard to mold allergies is to prevent mold growth by being vigilant about detecting early problems with leaky roofs, walls and cleaning up water damage right away. When there is a musty tell- tale smell, investigate right away and remedy the problem. For most people this is the end of the story. However, a small percentage of very sensitive people need to consult with an allergist who should investigate whether or not these people would benefit from allergy injections.
In some rare cases the affected person may have to relocate to another house that is free from molds.
More information about asthma: http://nethealthbook.com/lung-disease/asthma-introduction/
1.Shannon: Haddad and Winchester’s Clinical Management of Poisoning and Drug Overdose, 4th ed. Copyright 2007 Saunders
2. Zacharisen MC, Fink JN: “Is indoor “mold madness” upon us?” Ann. Allergy Asthma Immun. 2005; 94:12-13.
Last edited Nov. 7, 2014