Moulds are perhaps the most opportunistic of the microorganisms, and are found virtually everywhere, indoors and outdoors. They thrive wherever there is the least bit of moisture and nutrition - in fact, they are tiny, enzyme producing and cellulose eating factories. There is a mould for every occasion and almost every material. They work continually on organic materials, breaking them down. Moulds are vital in the process of decomposition and recycling of organic material, and are essential and beneficial for life. Indoors, however, where their populations can concentrate, moulds become a problem.
Fungi are the most frequent cause of biodegradation of building materials. This "biocorrosion" happens to building materials, such wood, chipboard and plaster, as organic and inorganic acids are released from the fungi. This is not surprising as fungi are capable of breaking down rock in nature. Ideal conditions for fungi growth are damp, humid conditions. In recent years, the opportunity for growth of fungi and hence mycotoxin release has increased with increased flooding and thermal modernisation of residential buildings. Allergies and mycotoxicosis can be caused by extended periods of mould exposure.
Mould growths can often be seen in the form of discolouration, ranging from white to orange and from green to black, and present many textures, including slimy, powdery and hairy.
Moulds have diverse effects on our health due primarily to their production of spores and toxins, some of which are Volatile Organic Compounds (VOCs). Symptoms caused by moulds range from allergies to liver cancer. Mould can also cause conditions such as Sick Building Syndrome (SBS) and skin infections. It is inadvisable for anyone to live or work in a mouldy indoor environment.
Much of the mould found indoors comes from outdoor sources. It is common to find mould spores in indoor air and growing on damp surfaces. Everyone is exposed to mould on a daily basis without evident harm. The spores are tiny and readily airborne. Their dispersal is assisted in the indoor environment by air conditioners, humidifiers and human activity. When inhaled in large numbers, they cause health problems.
The vulnerability of an individual varies greatly, and depends upon the nature of the mould material (allergenic, toxic, or infectious), the amount of exposure, and the susceptibility of the exposed person. Some spores are allergens and may trigger a full allergic response if the person is susceptible, causing symptoms such as red and watery nose and eyes, coughing, sneezing, itching, lowered blood pressure, rapid and strained breathing and increased heart rate. In severe cases, anaphylactic shock may occur, which is fatal without immediate medical assistance.
For humans and animals, the greatest danger posed by fungi is the ability for some species to produce mycotoxins. Mycotoxins are the secondary metabolites of mould and fungi and are a chemical combination of organic acids and aromatic compounds. Of the 300-400 mycotoxins recognised, only about a dozen receive regular attention for their potential threats to human and animal life.
There are two distinctly different indoor environments which harbour mould - mould reservoirs and mould amplifiers. A reservoir is where mould can be deposited and even accumulate, but will not necessarily multiply. Carpets are perhaps the best examples of mould reservoirs.
A mould amplifier is an environment which enables the mould to grow. This can be any material with a relative humidity of more than 65%, with the ideal range being 85% - 90%. The mould will flourish and is able to develop and release its spores. Bathroom ceilings or wet carpet become mould amplifiers. The prime area is in poorly designed bathrooms where the ventilation is via a small window.
Some moulds produce toxins. These varieties, such as aspergillus, penicillium, stachybotrys and arimonium, are water loving and their growth is harmful, but does not usually occur in concentrated amounts indoors. In order to grow, mould needs water, warmth and a food source. A leaky roof, burst pipe or other type of water penetration provides a moist area suitable for growth, especially if the area is never thoroughly dried out. Cellulose-based sheet rock, gypsum and other standard building materials provide a nutrient smorgasbord for mould. Many common building techniques can prevent moisture from drying up and incidentally promote mould growth. The problem is often exacerbated by tearing down a contaminated wall and enabling the mould and its spores to become airborne.
Mould contamination occurs most frequently in grouting and behind silica beading. The staining from mould growth is obvious in these areas. Overflow from pot plants may appear innocuous, but if an underlying surface such as carpet or matting becomes damp, mould will thrive. Stains can be removed, but if action is delayed, mould will permanently damage the carpet fibres.
Areas of major concern are those that have become water damaged from leaking pipes or rain. These areas are often overlooked until they start emitting unpleasant odours. By then the mould is already producing toxic chemicals - gases and allergens in the form of tiny spores and particles. If you identify any mould or water damage, act quickly. It only takes a few days for a serious problem to develop, not only in terms of health, but also in terms of cost, as both your health and the contaminated materials deteriorate quickly.
Exposure to mould spores is more serious than previously thought. The effects of moulds and dampness on the respiratory health of children are comparable to the effects of passive smoking and can also cause asthma and chronic bronchitis. In a recent US study of asthma in inner city suburbs, the mould Altenaria was found to be the single most important factor associated with the disease.
In damp and mouldy houses, people are more likely to suffer from rhinitis, nasal congestion, coughs, wheezing and sore throats. Mould exposure is associated with being more susceptible to colds, lower respiratory tract infections and irritation of skin and eyes, fever and headache. In severe cases, exposure can cause death.
Mould is being called "the asbestos of a new generation" in the United States and a rash of lawsuits totalling $US600 million is pending. A recent legal case resulted in the payout of $US3.1 million dollars by a company which did not adequately clean up a mould contaminated home.
Around the world, mould is identified in up to one third of buildings. Even in dry climates, buildings may be closed up, allowing the humidity to rise and mould to flourish.
Closer to home, in Perth, Western Australia, a family became ill with respiratory complications, debilitating fatigue and candida when their bathroom became contaminated by mould. When the problem was remediated successfully, their chronic health problems disappeared over a period of a week.
A number of residents are now taking action against negligent landlords. In one case, a family was exposed for 18 months to mould on ceilings and most of their walls. All seven people in the home were ill with respiratory symptoms and all the children were asthmatic.
Fixing the problem
Humidity is an important consideration when controlling mould, but a more important factor is water content at the surface. Humid air condenses onto a surface as it becomes cooler, as when a steamy bathroom cools down. Materials like cement, wood and carpets then act as sponges and become a breeding ground for mould.
By keeping indoor surfaces clean and dry, and maintaining a relatively low humidity, that is, below 50%, growth can be prevented. Regular and thorough cleaning of appliances where micro-organisms can grow, fixing leaks, repairing tile grouting, thoroughly mopping up standing water and eradicating damp areas (which also helps to decrease humidity) will deprive mould of its growing conditions. Regular and quality maintenance of air conditioning equipment is also necessary.
Disinfectants, bleaches and phenols combat most contamination. However, these chemicals are themselves known to have adverse effects on human health. A low toxicity solution is advisable so that you do not inadvertently replace one problem with another.
Remedial action is easier if guidelines are followed. Check regularly for mould in wet areas, including air conditioning systems. Any amount on the walls and ceilings can be toxic and requires remedial action. If you can see mould anywhere, other than in the tile grouting (where it is almost impossible to eliminate) you have a problem. If there is an earthy, musty, or "old sock" odour, you can assume you have a mould problem. You or someone else in your household may be experiencing symptoms such those previously listed. Look for previous water damage. Visible mould growth is found underneath materials where water has damaged the external surfaces, or it may be growing invisibly behind walls or in the roof. Look for discolouration and leaching from plaster. Don't go to the trouble and expense of testing as a first step in detection, as reliable sampling is expensive and requires equipment not available to the general public.
The major focus of any remediation is to first control the water or moisture at its source. Follow the water tract and eliminate it. Then remove the colonised materials or decontaminate the surface.
Cleaning small areas
Prepare a solution of vinegar with clove oil. Wear protective clothing, such as rubber gloves and a long sleeved shirt. Apply the solution to the mouldy area gently with a sponge or mop - spraying is not advised as it can cause spores to become airborne and spread to other locations. Allow the vinegar solution to stay in contact with the surface for 15 minutes or more. Ensure the treated area dries out as moulds will regrow if the surface remains damp. If the surface is solid (not flaking or absorbent), a simple solution of detergent can be used.
Ventilation systems should also be visually checked, particularly for damp filters, overall cleanliness and for damp conditions elsewhere in the system. Ceiling tiles, gypsum wallboard (sheet rock), cardboard, paper, and other cellulose surfaces should be given careful attention during a visual inspection. Stop any water seepage. To limit mould growth, you must respond to water damage within 24 to 48 hours with a thorough clean up, drying, and/or removal of water damaged materials.
If your home has large areas of mould, a professional contractor should be called as removal must be done by someone with specialist training. Tenants should immediately contact their landlord if mould appears in any part of the home. Deal with mould problems quickly. Acting swiftly with preventative measures will protect health and may avert litigation.
Dr Peter Dingle (PhD) has spent the past 30 years as a researcher, educator, author and advocate for a common sense approach to health and wellbeing. He has a PhD in the field of environmental toxicology and is not a medical doctor. He is Australia’s leading motivational health speaker and has 14 books in publication.