Some people are more sensitive to Damp and Mould than others, including:
babies and children
elderly people
those with existing skin problems, such as eczema
those with respiratory problems, such as allergies and asthma
those with a weakened immune system
I’ll start by explaining a bit about the different microbes and their spores that are present in the home. These are too small to be seen with the naked eye and it’s when they grow out of control that they may become a health hazard.
Moist building materials may support the growth of several microbes that are normally not present in indoor air. The growth of microbes depends mainly on the level of the moisture present and temperature conditions. It also depends on how nutritious the material is that the microbe is present in or on. However, in buildings, moisture is typically the only limiting factor. The presence of some of the microbes, especially mould fungi, have been associated with different health effects.
Indoor and outdoor air always contain several different microbes and their spores. In a normal building, the species present in the indoor air are the same as outdoors. However, in a moisture damaged building the range of microbes is different. Some species, referred to as ‘indicator microbes’, are typically found in moisture damaged buildings.
Hydrophilic microbes (microbes that have a special affinity for water) may grow only in very moist conditions, while xerophile microbes may grow in drier conditions. As a consequence, at an early stage of a moisture damage, the damaged material may be occupied by xerophile microbes who can grow and reproduce in conditions with a low availability of water. If the damage is prolonged, they are gradually pushed out and replaced by microbes that require moister conditions until only hydrophilic microbes remain. This phenomenon is known as succession.
Microbe growth in buildings may manifest itself in several different ways. Even if the growth is not visible, it may be recognized from a mouldy or cellar-like smell or from the symptoms of the people using the building. Microbe-related health effects may be caused by several factors including microbial volatile organic compounds (MVOCs), mycotoxins, allergens, and airborne microbe spores and fungal particles.
MVOCs are chemical compounds that are released when some microbes grow. In fact, they are typically the same compounds as the VOCs of chemical origin. MVOCs also cause the typical smell of mould. Mycotoxins are toxic compounds produced by some microbes. Stachybotrus, Fusarium, and Aspergillus versicolor are toxigenic. In addition, some microbes include proteins that are allergens, i.e. compounds that have the ability to cause allergy. Microbe spores and fungal particles may both cause symptoms themselves and transport toxins in the indoor air.
Aspergillosis is the name of a group of conditions caused by a mould called aspergillus mentioned above. This family of moulds usually affects the respiratory system (windpipe, sinuses and lungs), but can spread to anywhere in the body. Symptoms can vary from mild wheezing to coughing up blood and people with weakened immune systems are at a greater risk of being more severely affected. You can get more information from The National Aspergillosis Centre. They set out to better understand and diagnose and treat illnesses arising from damp homes. http://www.nationalaspergillosiscentre.org.uk/
Black Mould
Black mould is a generic name used to describe the Stachybotrys Chartarum species of mould.
Each type of microbe has unique preferences for the growth conditions. The growth of xerophile microbes may begin when the relative humidity of a material is 65–70 %. On the other hand, the probability of microbe growth on building materials seems to increase considerably when relative humidity exceeds 80 % . The relative humidity of 75 % seems to be a sensible critical moisture condition for microbe growth in buildings materials. For example, a typical xerophile microbe Aspergillus versicolor (which affects the respiratory system) has been reported to require a relative humidity of approximately 75 % for growth on a nutritious material at 20 ℃.
Dust mites especially love warm temperatures (23-27 degrees C) and high humidity levels of 70-80%. One study has found that mite populations stop growing and die out when relative humidity levels drop below 60%. Dust mites don’t drink as they get their moisture from the air. When the Humidity drops the dust mites dry out and die.
Maintaining relative humidity between 30% and 60% is a comfortable range for us humans with the temperature around 18-25 degrees Celsius. If you have a Humidity switched Extractor fan in your kitchen and bathroom set it for 60% RH.
Some other commonly reported mould or moisture related health effects are for example:
Irritative and general symptoms such as rhinitis, sore throat, hoarseness, cough, phlegm, shortness of breath, eye irritation, eczema, tiredness, headache, nausea, difficulties in concentration, and fever.
Infections such as common cold, otitis, maxillary sinusitis, and bronchitis
Allergic diseases such as allergy, asthma, and alveolitis.
The irritative and general symptoms in the first group do not cause permanent health hazards. The symptoms typically disappear within a few weeks after the end of the exposure. This is the same for repeated infections, but possibly not until after several months. However, a prolonged moisture damage may also lead to allergy or allergic hypersensitivity.
Reviewed studies show that there is a significant association between respiratory symptoms, especially cough and wheeze, and the presence of damp and mould.
Among other sources of moisture, one of the most common is condensation. Condensation forms when the air indoors can’t hold any more moisture. Cooking, showering, drying clothes indoors and breathing without adequate ventilation can all cause excess moisture. Droplets can form on indoor surfaces such as mirrors, windowsills and on walls, particularly when they’re cold.
You can help prevent the build-up of condensation by:
putting lids on saucepans, drying washing outside and avoiding using paraffin or bottled gas heaters
opening the bedroom window for 15 minutes each morning
making sure your home is well insulated
heating your home a little more
ventilating rooms regularly and leaving doors open to allow air to circulate, unless you’re cooking or showering
if you’re cooking, showering or bathing – opening the window, putting the fan on and closing the door of the room you’re in.
For those of you interested in the effects of dampness and mould on your quality of life and living conditions I would suggest you download ‘WHO guidelines for indoor air quality: dampness and mould’. https://www.who.int/publications/i/item/9789289041683
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