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School of Engineering & Advanced Technology
Links between mould and health in New Zealand
homesAssociate Professor Robyn Phipps
Mould in homes
Moulds are ubiquitous in NZ homes
45% of NZ homes have visible mould
Mould are detrimental to the health of occupants and building structure
Why are NZ homes mouldy?• High rainfall, high humidity, wind driven rain• Lack of house maintenance• Construction defects• Poor construction and cold homes• Floods
House condition survey (Branz 2005)
• Deferred maintenance of $4500 per house for house components rated as poor to serious
• Extrapolated to a national maintenance deficient to $4.5 billion
• Yet on average NZers spend less than $1300pa on home maintenance
• Need to build in tolerances and resilience for lack of maintenance
Mould related symptoms
Eye irritation, runny nose, sneezing, coughing, nausea and diarrhoea,
Headaches, fatigue, inability to concentrate, constrictions of airways, skin irritations, respiratory congestion, shortness of breath, wheezing, aggravation of asthma
The link between dampness and health is proven.
People most at risk• Infants and children less
than 2 years old and elderly• Compromised immune
systems• Chronic inflammatory lung
disease such as asthma, hypersensitivity pneumonitis, severe allergies
• Those recovering from recent surgery or illness
Moulds are microscopic in size ranging from 2-20 µm (micron)
Their tiny size makes them easy to inhale, but also difficult to find, filter, identify and remove.
Stachybotrys chartarum
• Over 6000 genera of fungi, and about 1.5million species of fungi, of which only 69,000 have been described.
• The health effects of most species are largely unknown
• Fungi share many basic characteristics of genetic makeup similar humans, but the belong to a kingdom distinct from plants and animals.
• Consequently the biocides commonly used to kill fungi can also do damage to human cells
Mould GrowthMoulds are close to the perfect organism.
Hyphae are able to transport nutrients and water across great distances from areas of rich to short supply
They are highly efficient digesters of organic substances (solid, liquid or gaseous)
High degree of environmental adaptability – due to hybridisation, genetic mutation, and environmentally induced non-genetic mutation
Nutrients• Fungi produce exo-enzymes that can
digest complex organic compounds into smaller molecules.
• Fungi enzymes are able to digest almost any natural material and can have almost limitless growth
• There will always be sufficient nutrients for fungi to grow in a home
• Porous materials need to be dried within 48 hours of getting wet or they should be discarded. This includes gypsum plaster board, carpet, insulation and documents.
• Non porous materials can be cleaned
They have evolved to fight off and/or be defensive of other colonies for available nutrients and some species do this by producing mycotoxins.
Aflatoxins are potent carcinogens.
Therefore they evolved resistance to many of the biocides.
Mould growth• The most limiting
factors to mould growth are temperature and water availability
• Fungi can go dormant and wait out dry or cold periods
Mould classification systems• Grade 1 normal• Grade 2 visible mould less than 1m2 -
cleaning to remove mould• Grade 3 visible mould 1 to 10m2 - small
remediation job• Grade 4 visible mould greater than 10m2 -
large remediation job• Grade 5 strong signs of mould - not visible • Grade 6 cross contamination• Grade 7 clean room
• Grade 3, 4 & 5 jobs require a complex remediation process including;
• containment, • negative air pressure, • PPE for workers, • air scrubbers,• Systematic and thorough
cleaning and vacuuming of non-porous materials
• Safe disposal of porous materials
Thank you for your attention
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