By Angus Dalton
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We inhale about 15 cubic metres of air every day, and you can bet that air contains a good dose of mould spores. We live in a fungal world, and mould in particular grows in at least 30 to 40 per cent of our homes and office buildings.
But when does it become risky to health? And is the much-reviled black mould really the most toxic and dangerous of them all?
A roof in Randwick, Sydney, infested with mould and black mushrooms after tenant Holly reported a drip five weeks ago.Credit: Janie Barrett
It turns out our understanding of this issue was warped by bad science undertaken by the US Centres for Disease Control (CDC) way back in the ’90s.
The toxic black mould myth
Fear of toxic black mould still infects public consciousness. But as far as the evidence goes, black mould (the species Stachybotrys chartarum) is no more harmful to human health than any other kind of mould.
The demonisation of Stachybotrys began in the mid-90s with a cluster of 139 babies coughing up blood in eastern Cleveland, Ohio. The infants were diagnosed with pulmonary hemosiderosis, or bleeding lungs. At least 12 died.
A CDC investigation linked the sick babies with homes contaminated by Stachybotrys. Intense media coverage of the CDC’s study ingrained a public paranoia of black mould that would last decades.
But as black mould became the boogeyman, concerned scientists within the CDC assembled a taskforce to scrutinise the study. They uncovered several flaws.
The initial study calculated that for every 10 colony-forming units (spores captured from the air and grown on agar plates) within one square metre of a home, the chance of a resident infant having pulmonary hemosiderosis was 9.8 times higher.
But the airborne mould concentrations were calculated incorrectly. When reviewers corrected the mistake, the calculated risk almost halved.
Hidden black mould revealed after renters pulled a couch from the wall, submitted to the Facebook page Don’t Rent Me.
They also discovered a suspicious sample taken months apart from the others, which had a wildly different diversity of fungi. Worried that the time of year had affected the sample, or that a different sampling method had been used, they discounted it from analysis. Doing so reduced the odds ratio from 9.8 to 1.9.
And there was another clanger. The study was supposed to be “blind”, which means scientists take measurements without knowing which study sites are the controls to reduce bias. But one investigator admitted they knew which houses the sick babies were from.
Not wanting to miss any spores, the investigator pounded air ducts and furniture, stirred up dust, and took twice the number of samples in the sick babies’ homes compared to the control houses. That totally skewed the data.
As a result, two teams of reviewers concluded the link between black mould and sick babies was inflated, statistically unstable and unproven.
The debate around health risks
That’s not to say black mould is safe to be around. The truth is mould of any species and colour can release spores, fragments and toxins that pose health risks.
The black mould saga highlights the challenge in investigating these health risks, because it’s very hard to accurately measure spores in the air.
Measurement methods have error rates between 30 and 200 per cent, and the concentration of airborne mould can fluctuate by a 10,000-fold difference over a single day.
That makes it hard to tie a certain level of mould to any one symptom. As the federal Health Department points out: “A causal relationship to any health effect from exposure to indoor damp or mould in the general population is yet to be established.”
Holly Konopka in her rented Coogee apartment. She has had to move her bedroom furnishings into the lounge room because of mould growing on the ceiling. Credit: Janie Barrett
In a 2018 parliamentary inquiry into biotoxins, the real estate industry seemed to use this uncertainty to hose down fears people had about living alongside mould.
The Real Estate Institute of NSW (REINSW) told the inquiry there’s “a general unwarranted fear surrounding the identification and presence of mould with little medical or scientific evidence to support such fear”.
(A spokesman for the organisation told me that conclusion was based on a New Zealand report into the dangers of living in a house previously inhabited by people who smoked meth, which included a section on mould. The report was not available.)
It’s true many of us live alongside mould with no obvious issues. But just because we don’t know how much mould makes us sick doesn’t mean it’s safe to live with.
Three reviews – including one produced by the World Health Organisation – have confidently linked mould and dampness to coughs, wheezing, respiratory infection, allergic rhinitis, eczema, bronchitis and the serious lung disease hypersensitivity pneumonitis.
“If you’re perfectly healthy, and you have a lot of mould in the house, you can still get very, very sick,” says Dr Heike Neumeister-Kemp, an international expert in indoor mould.
Landlords behaving badly
People who have lived with mould long-term told me they experienced headaches, coughing, hallucinations and vomiting.
One man was diagnosed with mould-induced hypersensitivity pneumonitis, which cut his lung capacity by 50 per cent and left him reliant on an oxygen mask during flights. Industrial testers later found mould in his basement.
It’s clear mould should be removed from people’s living spaces as quickly as possible.
Sydney renters living alongside entire walls contaminated with mould.
Yet dozens of renters I spoke to had to go through a tribunal to get drips, leaks or poor ventilation – the underlying causes of mould – fixed. One group of housemates won $5000 from their former landlords for living alongside mould-covered walls, but the landlords simply never paid.
It’s obvious some landlords and property managers continue to dismiss or downplay mould contamination. (One woman was told the dark stain on her bathroom wall was “mould-like dirt”. Curious, then, that it grew back every two weeks.)
But the WHO is clear: there’s enough epidemiological evidence to show mould increases the risk of respiratory illness, asthma, serious lung infection and “diverse inflammatory and toxic responses”.
Landlords are responsible for ensuring homes are free from drips and leaks, and they must ensure rooms and bathrooms are well-ventilated with working fans and windows, the spokesman from REINSW said.
Says Neumeister-Kemp: “The WHO has said we shouldn’t have mould in any building. So if you can see it, do something about it. If it’s wet, dry it. If it smells, go find out why.”
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