Moulds are a form of fungi that help to break down organic material and can grow indoors or out on nearly any surface, from food in the fridge to building materials left out in the rain.
When mouldy material is disturbed, spores are dispersed into the air and can be inhaled. The worst offender is stachybotrys chartarum, a greenish-black mould that grows easily on drywall, drop-ceiling tiles and wood, and which is known to have health effects.
Health Canada guidelines endorse a ban on indoor moulds, noting that “exposure to fungi in occupational environments causes allergic and toxic diseases,” but there is no official policy on testing for mould in schools or workplaces.
Even when tests are carried out, they can be inconclusive: Most tests begin with air quality, which is problematic for a number of reasons, including the fact that the indoor environmental and air-quality industry is unregulated in Canada. Consultants can pick and choose from a patchwork of standards set by industry groups, which do little to scrutinize members' quality of work, said Bruce Stewart, senior vice-president at Pinchin Environmental Ltd., a Mississauga-based national environmental-consulting company.
According to Mr. Stewart, 80 per cent of indoor mould grows in wall cavities and other hidden places. Buildings that have had water leaks, a fire or poor air quality are the most susceptible.
“When it starts growing inside, mould is a symptom of a building system that is failing,” said Om Malik, an industrial hygienist and indoor-air-quality expert who heads the Mississauga-based firm Environmental Consulting and Occupational Health Management Inc.
One thing known for certain is that water is a major factor.
“Mould and moisture are interchangeable,” Mr. Malik said. “You have to find the cause of the moisture.”
Once the moisture source – often a leaky roof or wall – is taken care of, any mould-ridden areas of drywall, carpeting or insulation should be cut out and patched with new, clean material. Do not try to scrub or clean the mould away, Mr. Malik warned. Even bleach is useless, as it targets only bacteria, not fungus.
Leaks of what he calls “black water” – extremely contaminated water from something like a sewage backup – leave only a six-hour window for cleanup before mould begins to grow. “Grey water,” mildly contaminated rainwater, or sink or toilet overflow, will lead to mould growth within 12 to 24 hours. With clean water, the window is 48 to 72 hours.
But the best way to deal with mould, Mr. Malik said, is to stave off its growth in the first place: “If things get wet, we must dry them.”
