Fungi love the wet but what are the health consequences?
In Sydney and in the surrounding country areas of NSW, Australia, we have recently experienced several weeks of storms and very heavy rain. In our local area, this was preceded by a weird mini cyclone where a very large number of trees were blown over or uprooted. The sounds of tree lopping fill the air and damage to roads, houses, parks, and recreation facilities has been considerable.
Cities, towns, and homes near rivers have suffered enormous damage and whole towns will have to be rebuilt. The health consequences of this are especially dangerous in areas where sewerage systems have been broken and raw sewerage has seeped into water supplies, crops, and golf courses to name just a few places. But what of the moulds and fungi that flourish in wet environments? Are they a risk to health and if so, what can and should be done?
When we go out into the garden or perhaps walk along a bushland path, we are likely to see mushrooms and toadstools. If like me, you can’t identify the toxic forms from the non-toxic, don’t touch any of them! I had a mass of small, yellow fungi grow up in one of my plant pots last week, but they disappeared as quickly and mysteriously as they appeared.
Fungi are classified by scientists as their own ‘Kingdom‘ – they are neither plants nor animals. They include many species that are used in the manufacture of foods, including alcohol, cheeses and breads and many types of mushrooms that are eaten as foods. Many are also used to produce medicines.
Moulds and Mildews
Moulds and mildews are the more common fungi around and in our homes. We often see mildew growing on the leaves of flowering plants (usually powdery mildew) or on grapes and potatoes (downy mildew). However in very humid conditions, mildew likes to come inside and grow on our clothes and some furniture . Mildew is always flat, is grey or white and has a mild smell that we might call ‘musty’. It can give us a slight respiratory reaction but it’s more a nuisance than of any danger to us.
Moulds on the other hand, can be dangerous to the integrity of buildings and to our health. Apparently more than 10,000 different species of mould can live indoors but most commonly, there are six types: Alternaria, Aspergillus, Cladosporium, Penicillium, Chaetomium and Stachybotrys. The last two of these have recently been identified as the cause of serious but underdiagnosed health issues.
Alternaria is primarily an outdoor fungus found in soil. It is blown around in the wind on dry, warm windy days and is often responsible for outdoor allergy reactions. However, like most fungi it grows in damp conditions and is often found on materials such as paper and cardboard when they have been exposed to damp environments. If you find you are coughing and sneezing when you are reading an old book, then this could be the cause! Alternaria also grows on walls and around windows, under sinks and other damp places and especially in shower recesses.
Buildings that have suffered some type of water damage are very likely to have an infestation of Alternaria and this may be one of the causes of ‘sick building syndrome‘. This mould can be coloured black, grey, or dark brown and has a woolly type of texture.
Aspergillus is the most common type of indoor mould. It can grow on bread as well as on walls, paper, and clothing. It can vary in colour from yellow to green, grey, black, brown, or white depending on the species.
Cladosporium differs from the other household moulds in preferring a cool environment. It isn’t likely to grow in the bathroom but prefers to grow on fabric such as curtains and wood surfaces like flooring. It is black or green.
Penicillium is well known because it led to the discovery of the first antibiotic. It grows on materials that have been wet from contact with water. This includes a large range of materials from carpet to mattresses and is likely to be prevalent in flood damaged houses and their contents. It is blue or green and produces strong, musty odours.
In some cases, being exposed to mold for extended periods of time can cause very serious, and even life-threatening, health complications.
Chaetomium mold produces high quantities of toxic substance known as biotoxins or mycotoxins. These toxins can be breathed in or absorbed through the skin and are the cause of many serious mold-related health symptoms.
Chaetomium can cause skin and nail infections, brain infections, serious ongoing allergic reactions, and asthma. Recently, autoimmune diseases such as lupus and multiple sclerosis have been linked to exposures to Chaetomium mold.
Stachybotrys chartarum, known as ‘black mould’ is rated as the most dangerous type of household mould. This is the mould that grows in areas that are constantly wet. In your home, this could be mould under the house if there is a place where water collects or areas around leaky pipes or inside air conditioning ducts where condensation collects.
Risks to houses and their contents
A little like the children’s story of The Three Bears, we and our homes need the humidity to be not too dry, not too wet but JUST RIGHT! If our homes are too dry our furnishings and our health suffer but probably being too wet is more of a problem. Fortunately, most of us can easily equip ourselves with fans, air-conditioners, air-purifiers, humidifiers, or de-humidifiers (whichever is needed) to balance the humidity to a comfortable level. But we should keep aware of the humidity and develop habits to make sure that our homes don’t become mouldy. Simple habits such as always wiping the shower recess area after use and running a fan until all steam and condensation is removed from the bathroom are essential.
Risks to health from moulds
Indoor dampness and the moulds that grow in damp environments cause respiratory problems in many people but particularly in young children. There are a range of allergies, hypersensitivity responses and asthma that are recognized as mould-related health problems throughout the world. Of the common mould types Aspergillus may cause the most indoor allergic reactions. It also causes infections and inflammation in the lungs of people with weak immune systems. Cladosporium can also cause of range of respiratory problems while Penicillium usually causes relatively mild allergic reactions.
Unlike the relatively benign effects of the other moulds, Stachybotrys chartarum and Chaetomium globsum produce mycotoxins. These toxins not only cause the usual allergic types of responses but symptoms that include recurring flu-like symptoms, coughing, chronic bronchitis, sore throat, diarrhoea, fevers, headaches, chronic fatigue, rhinitis, neurological symptoms and general malaise. Approximately 70% of people with confirmed exposure to toxigenic moulds exhibit neurotoxicity. The toxins released by S. chartarum are extremely toxic to nerve cells and in addition to being neurotoxins, they suppress the immune system leading the affected person more vulnerable to other infectious agents.
The mycotoxins released by these moulds underlie a debilitating illness currently known as ‘Chronic inflammatory response syndrome’ but research in this area is limited. One recent publication ‘Fungal toxins and host immune responses‘ attempts to summarise our current knowledge.
Fortunately, it seems that people usually recover once the fungal exposure is removed but this takes time. The key message is to make sure you are not living in an environment that harbours fungi.
Not all bad!
Like most things in life, fungi have their very good and very bad side. We humans need to understand and respect our fungal friends and make sure we are creating living environments where we can all live together in harmony. Building in flood plains is clearly not an option as is having a home with insufficient ventilation.