The key to preventing household mould is reducing moisture, rather than using expensive mould removal products.
It’s been a wet few years around Australia. Flooding and heavy rain have been widespread throughout the country, and they’ve brought with them a noxious piggy-backer – mould.
Mould, a type of fungi, serves an important purpose: to break down organic matter. Outdoors, it is an important part of our ecosystem and is a necessary waste removal mechanism. “If there was no mould on earth our rubbish tips would fill up, there wouldn’t be rotting or organic matter, and we’d have a lot of waste,” says Cedric Cheong, an environmental scientist and a director of mould investigation company Mycologia.
Indoors, however, mould is an unwelcome intruder – aside from possible health problems associated with mould exposure, it can damage clothes, shoes and textiles, and generally looks unsightly. And despite all the advertised claims of their killing power, off-the-shelf mould cleaners may not be the best way of dealing with an outbreak.
For more information about floors and surfaces, see Laundry and cleaning.
Health impacts of mould
Mould is particularly problematic for the young, elderly or sick, and those with asthma and allergies. And an allergy to mould can develop as a result of high mould exposure, says Professor David Guest of the Plant Pathology Faculty of Agriculture and Environment at the University of Sydney.
In addition, moulds can trigger severe asthma attacks in those living in mould-affected homes. “Patients would have an asthma attack, they’d go to hospital, their symptoms cleared up after a few days, they’d go home, and they’d have another attack,” Prof Guest says. “When nurses went to their homes they found a lot of mould… we found that the two things to do were clean up the mould, and address the problem causing the mould to grow.”
Dr Sheryl van Nunen, spokesperson for the National Asthma Council Australia and Clinical Associate Professor of the Sydney Medical School – Northern, says asthma is made worse by the presence of mould. “It increases your asthma symptoms in several ways. You can be sensitive to mould, and it can irritate you further. Sometimes moulds can infect the sinuses, they can grow within the nose for example, and patients need to get the fungus removed surgically.” In rare, worst-case scenarios, moulds can invade the lungs, taking root inside the body.
Even in otherwise healthy people, mould can create health problems. “The problem is that if you have a genetic predisposition, or if you’re exposed to high levels of mould spores over a long period… you can develop the allergy,” says Prof Guest.
Prof van Nunen says: “About 50% of people who live in mouldy conditions will have upper respiratory symptoms, a non-allergic rhinitis that presents like hay fever,” she says.
Associate Professor Dee Carter, of Sydney University’s School of Molecular Bioscience, says one of the most interesting cases she has ever dealt with came from the curator of a local art gallery. “She had been sent an ‘artwork’ to exhibit, which was an upholstered armchair that had food liberally applied to it. The concept was a piece of living art that would change over time as things grew… The poor curator called because she was in a smallish gallery and was feeling more and more ill due to the growing mould and the volatiles it was making. The gallery was closed and the armchair doused in bleach, wrapped in plastic and taken to the tip.”
Commercially available mould cleaners
While most commercially available mould killers use bleach as an active ingredient, several sources tell CHOICE they do not work effectively.
Although there’s evidence that bleach can kill fungi, the concentration of bleach in products marketed as mould killers, including Power Force Mould Away, Woolworths Mould Cleaner, Coles Ultra Mould Remover, Selleys Rapid Mould Killer and Exit Mould, is less than five per cent. Bleach has a short shelf life and loses potency quickly, so the longer products sit on shelves, the lower their bleach concentration becomes.
A product that starts out with a concentration of about four per cent states on its packaging that by the end of its shelf life it may contain just 0.6% bleach. Experts we spoke to recommend a 10% bleach concentration for killing mould. “Over time [what is] in the bottle will change,” says Cheong. “Bleach concentration will also change. Manufacturers usually put the bleach at a higher concentration initially, but on the shelf it decreases.”
In addition, several of our experts claim bleach is in some cases a masking agent. “Bleach takes the colour, the melanin, out of fungi, making it invisible,” says Cheong. “You can’t see it there anymore, so you think [the bleach has] done its job. But it hasn’t necessarily – you’ve taken the colour out, but the growth may still be there. Strong bleach is also harmful to grout and tiles as it erodes and corrodes the surfaces, making them more porous. You’re eroding initial surface protection, which makes [surfaces] more vulnerable to further fungi growth. That’s why we don’t recommend using bleach.”
Prof Carter says bleach, so long as it’s active, is a good way to kill off surface growth and spores on non-porous surfaces, but will not penetrate porous materials, contrary to claims made by several products we purchased. “If the mould is growing on plaster or grout or wood it will kill mould on the surface, but not below it.”
can be an effective and cheap means of dispatching mould.