Mould and Your Home - Cont'd

Neil McManus with NorthWest Occupational Health and Safety (www.nwohs.com, 604-980-8512) discusses whether B.C. residents should be concerned about the presence of mould in their homes. Mr. McManus holds a B.Sc. in chemistry, a M.Sc. in radiation biology, and a M.Eng. in occupational health and safety engineering, a B.Ed. (Chemistry and Biology) and certifications from the American Board of Industrial Hygiene (Certified Industrial Hygienist) and the Canadian Registration Board of Occupational Hygiene (Registered Occupational Hygienist). He has almost 25 years of field experience. (Industrial/occupational hygiene is the professional discipline devoted to the anticipation, recognition, evaluation, and control of health hazards in the workplace and in the community.)

We tend to forget that we live in a temperate rainforest. That liquid snow that we don't have to shovel during the winter and most of the year, for that matter, is an insidious enemy to all homes. One need only walk in the abundant forests in our midst to view the effects of mould in the ecological cycle of growth and decay. Moulds are decomposers. Without them, organic carbon would not recycle. Our planet would be uninhabitable. When they cause problems in our homes, they are only doing their jobs. They were here first. We humans with our attempts to control nature through our living accommodations, and so on, are the interlopers.

Most moulds prefer room temperature for growth. Their favourite food is cellulose. Our homes contain lots of cellulose: in paper, fabrics, wood structures, settled dust, gypsum board, and so on. Moulds also need for growth, moisture in the air and the substrate on which to grow. They prefer airborne humidities in the range of 60% and higher. These are the typical conditions in which we, humans, prefer to live. In light of these facts, is it any wonder that moulds are part of our everyday surroundings both inside and outside our homes?

The earliest references to moulds in dwellings are biblical. Residents of that time were advised to maintain their dwellings in a state of cleanliness. So, if moulds have been with us throughout our history, why then is there the emphasis on them now? Well, that's a question that many people are pondering. Below are some of the things that can result in mould growth in the home:

* Our choice of building materials: older homes contain old-growth wood  that contains anti-fungal components. New homes have chipboard.

* Most homes of today have carpets. Carpets have a three-dimensional structure. That three-dimensional structure provides the quiet, dark, moist environment that many moulds prefer. Carpets laid on concrete in basements receive moisture diffusing up from the soil underneath.

* Lack of sufficient overhangs that do not protect walls from driving rain.

* Improper installation of windows. The result is that the slope at the top of the frame, instead of directing water away from the building, directs flow toward the wall.

* Sealing houses and residential buildings to keep the heat in. Keeping the heat in invariably keeps in the accompanying moisture.

The humidity of the air is the moisture it contains. Relative humidity is the humidity compared to the water-carrying capacity of the air at that temperature, expressed as a percent. Since the higher the temperature the more air holds moisture, our warm homes combined with our activities make for moisture saturated air. Most homes exert little control over interior moisture. The last thing we need is condensing levels of humidity indoors. Air in bathrooms becomes saturated when we take showers because of the presence of airborne droplets of water. These result from bounce back following collision with body surfaces. The other place is the kitchen. That kettle, that is allowed to boil too long coating the windows and interior wall surfaces in a film of moisture, is an obvious source. So also is the electric clothes dryer that vents to the basement or crawlspace in order to save money on heating, instead of outdoors. The latter is false economy, since this provides the moisture needed for growth of mould.

Buildings often lack proper maintenance including paint or stain rejuvenation, and caulking around windows to limit moisture and damaged roofs. The consequences of not fixing a damaged roof are great. Prolonged growth of moulds in wall cavities due to an unrepaired roof can lead to pancaking and other structural collapses.

Mould allergies are well known. They manifest themselves through hay-fever-like symptoms when the upper airways are involved: irritation of eyes, nose, throat, runny nose, non-productive cough, and nosebleeds. About 16 to 20 percent of the population are more susceptible to develop allergies than other people. If and when people develop an allergy to something is not predictable. Once people develop allergies, they are sensitive to very small levels of the test challenge.

If the allergy affects the middle airway, the result is allergic asthma. An allergy can affect the bottom of the respiratory tree where gas exchange occurs. This condition is called extrinsic allergic alveolitis or hypersensitivity pneumonitis or farmers' lung. So, if this condition affects only farmers, why should city slickers be concerned? Well, this condition is a result of exposure to mould spores. And, as noted previously, moulds can easily gain a foothold in our homes and places of work if we give them the opportunity.

Some people develop mould related conditions that are building related. This means that the condition gets worse when they occupy a certain building and gets better when they are away from it. People have been affected by mould in their places of work, as well as their homes. Condo owners have forfeited everything in an attempt to try to better their health by abandoning their leaky homes. They then end up in basement suites that often are damp because of lack of moisture control and contain carpeted concrete floors that harbour mould. Allergic processes are unforgiving of one's circumstances.

Chronic fatigue seems to be associated with mould exposure. What that means is that a person sleeps a lot, especially on weekends. I know from personal experience. Can one overcome this? The answer, fortunately, seems to be yes. Minimize the exposure to mould spores in the affected premises. This is the only solution.

Exposure to mould also appears to be related to impaired information processing (cognitive function). This means that short term memory is impaired and the person garbles such things as strings of letters and numbers in telephone numbers and web addresses, among other things. The ability of these people to earn a living in the information-processing-intensive society in which we live is severely impaired. This situation is receiving increasing attention from researchers in this field. If this correlation is shown to be true, this is a bridge that none of us should allow ourselves to cross. There appears to be no going back. Individuals afflicted with this condition are engaged in battle for disability pensions with the workers' compensation system over inability to work because of an as yet unrecognized condition, and in the courts over dwellings in which they cannot live in comfort and good health.

Some members of the Aspergillus family of moulds can grow at body temperature. This means that they can grow inside the passages of the respiratory system in the lung and possibly the sinuses. Fighting a mould infection within the body is extremely difficult because agents that kill mould cells can damage human cells as well. An internal mould infection is extremely serious.

So what can the homeowner do about this? There are two key actions: keep it clean and keep it dry. By now, it should be obvious that we have little control over growth of mould, given the climate in which we live. Is it possible to have a house free from mould growth? The answer is a qualified yes. Through attention to detail, we should be able to eliminate all visible mould growth. Visible growth is a large colony formed by many cells. Mould colonies start from individual spores. Hence, the colonies are invisible until they become large enough to see and recognize.

Mould growth is not the same as mould spores in air, since air transport of spores is the way the mould plant 'seeks' new growth opportunities. Hence, without maintaining a controlled environment, keeping spores from the interior of a dwelling or place of work is impossible. Spores are present in widely fluctuating levels in outdoor air. Every time we open a door or window (remember all that fuss about indoor air quality and windows in work buildings that cannot be opened?) spores enter the premises.

The hardest place to control moisture is the bathroom. Bathrooms containing tubs and shower enclosures must have a fan to remove moisture. Opening a window in a bathroom lacking a fan in cool or cold weather merely cools interior surfaces so that condensation can occur. Also essential to removing moisture is wiping down the tiled area around the bathtub with a cloth after taking a shower. There can easily be 10 times as many mould spores in the air in the tub area as anywhere else in the house. I know from measurement experience. As well, mildew (a form of mould) that develops in and around shower enclosures and at the tub-wall interface must be killed. Products for performing this task are available in the supermarket. Be sure to follow directions!!

Poor drainage is another concern. Water seepage into basements and crawlspaces provides the moisture needed for growth. Crawlspaces under homes and industrial and commercial buildings are major habitats for mould growth. A vapour barrier is essential to prevent entry of moisture from the ground.

Brush that is allowed to grow near buildings is another source of problems. Foliage prevents passage of sunlight and air motion needed to dry out soil and building surfaces. As well, roots can enter, and impede and affect drainage systems.

Duct kitchen and bathroom fan discharges, and clothes dryer discharges outside the building. This may require discharge through the roof if air circulation at the point of discharge is inadequate because of confinement by walls and other structures (horizontal venting may not exhaust moisture to the outside).

Use a high efficiency filter in the furnace (about $15). Homeowners with gas furnaces that circulate the air have a tremendous advantage over those with other forms of heating in this battle. The furnace circulates the air through a defined path in ducts. This provides the opportunity to remove spores from the air through a filter or electrostatic air cleaner. In addition, the turbulence created by the moving air renders some spores airborne potentially enabling filtration. In my household, a high efficiency filter stopped a long-term non-productive cough likely due to mould spores in air within one hour following installation.

In homes lacking a circulating fan, portable HEPA-filtered (High Efficiency Particulate Air) air cleaning devices can provide some benefit. Unfortunately, the spore must reach the filter before reaching the nose in order to produce benefit.

Remove dust from horizontal surfaces. The dust that is carried on air currents and settles in our homes is mostly cellulose. Since cellulose is the favourite food for many moulds, growth in dust and fluff that has been allowed to accumulate should be expected.

Vacuum cleaning is another major defensive strategy. Recent additions to the family of home vacuum cleaners have HEPA filters. HEPA filters stop tiny particles in air including spores. Hence, a HEPA filter coupled with high suction in a vacuum cleaner provides the means to remove mould spores and the plant itself from carpets. Keeping carpets clean through vacuuming is essential to minimizing exposure to spores.

So, what should one do in a situation where mould growth is extensive? This happens in grow ops and similar crime scenes where abandonment occurs, but also in situations where leakage and growth develop during absences, such as vacations, and so on. There are as many legitimate reasons for development of extensive growth of mould as there are illegitimate ones. Many people don't have support from an insurance company. This is especially the case where the situation occurred as a result of criminal activity.

Where insurance companies are prepared to shoulder the cost, external consultants, such as industrial hygienists, often are brought in to liaise with the restoration company. The consultant will examine the premises and assist in developing the scope of work to be performed, and ascertain that it has occurred successfully and appropriately.

Increasingly there are circumstances where insurance companies refuse to shoulder the cost, despite the assumptions of homeowners about coverage of their policies. Be sure to read your policy to determine what is and is not covered. In these circumstances, many homeowners decide to perform the work themselves. There is nothing wrong with this decision as long as you do your homework first since removal and disturbance of mould-infested materials can lead to spreading of spores throughout the structure. This can jeopardize the health of the cleaner and occupants and could compound the existing situation. In addition, building materials in older homes (pre-1980) are likely to contain asbestos. Homeowners planning to do-it-themselves should seek guidance about safe work practices. Some consultants will share this information.

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