Black Mould: Causes, Health Risks & Solutions
Are you still putting up with the black mould that is growing by the day in your bathroom? Many property owners, tenants and landlords tolerate it – viewing it as unsightly but harmless. As a result, it is often overlooked and does not receive nearly enough exposure.
That black mould growing and spreading further along the sealant and into the corners every day does look unsightly, but it also has real health implications and is a worrying health concern for all of us – or at least it should be.
When we go to a silicone resealing job the customer always asks, “Why does bathroom silicone get so mouldy?” In most cases that we deal with the primary cause is quite simple; poor ventilation. Poor ventilation is one of the primary drivers of mould growth. Bathrooms tend to be used frequently and, particularly when showers are used, quickly become very steamy, humid, and damp environments. If there is no system in place to ventilate the bathroom, the moisture will remain suspended in the air and as it cools and the vapour droplets become larger, they will descend and settle on the surfaces – including the silicone sealant – eventually providing the ideal conditions for an eruption of mould growth.
Many clients are surprised at the health implications of the black mould – which may be black, greenish-black, or greyish-black in colour – growing in their bathrooms. Yes, they know it looks terrible and often report the lingering stale potent smell of the mould – often likened to wet soil or wet, decaying cardboard. This odour builds up in the bathroom due to a lack of ventilation – which is often also the cause of the slimy, sometimes furry-skinned, mould growth in the first place. However, the health implications of the black mould should be much more of a concern than either appearance or odour.
There are many different varieties of mould which we find growing in damp environments such as our bathrooms – some are less dangerous than others. However, all types can trigger allergic reactions and all can cause a marked deterioration in the health of individuals with existing respiratory conditions. Some of the most common moulds you can encounter in your bathroom are Aspergillus, Cladosporium, Penicillium and Stachybotrys – or black mould as we all know it. There are, at least, one hundred and twenty-three species within the black mould genus. Arguably, the most dangerous of those which take over our damp and humid bathrooms is Stachybotrys Chartarum.
While many moulds can and do emit toxins, Stachybotrys Chartarum is different. As a filamentous fungi, it can produce mycotoxins. Mycotoxins are toxic chemicals and can cause serious health problems if inhaled or ingested and can affect our internal organs.
Stachybotrys chartarum, known more widely and simply as black mould, thrives in the moist environment of a bathroom or shower. Stachybotrys chartarum has a fondness for silicone sealant and thrives on particles of dead skin, soap scum, shampoo residue, natural body oils, body fluids, sweat, body oils and rinsed off moisturising products. These are all perfect food sources for Stachybotrys chartarum and the silicone sealant provides the perfect gathering place for all these elements.
The silicone sealant is by its nature porous, which in turn allows the surface layer to trap water, moisture, shampoo residue and all the other elements mentioned. This layer of organic material – often not even visible at first glance – is like a buffet meal for the mould. Additionally, a poorly ventilated bathroom such as some of those in Edinburgh’s older tenement buildings adds enormously to the issue. Many of these tenements were often built without an indoor bathroom or toilet and the bathrooms have sometimes been converted from an internal cupboard and have no window for air circulation. After a hot shower you have perfect damp and humid environment for the black mould to spread across the bathroom.
In a short space of time your bathroom silicone can go from new to slightly discoloured silicone – often pinkish or orange – as the layers of residue build up and then, shortly after, you have black mould patches appearing on the silicone seals and climbing the grouting around the tiles. In no time at all it will be reaching for the moisture on the ceiling above. It is a nightmare for homeowners and tenants alike. A potentially deadly one.
Those most at risk from black mould are children who still have developing respiratory systems, the elderly who may have weakened immune systems, and other individuals with weakened immune systems or pre-existing respiratory conditions that make them more susceptible to the harmful effects of mould exposure.
Moreover, all black mould releases spores that can irritate the airways, leading to coughing and shortness of breath. Inhaling, ingesting, or even touching mould or its spores can also trigger allergic reactions such as congestion, a runny nose, sneezing, and skin rashes – so never touch it with bare hands or skin. Black mould can also exacerbate other medical conditions such as asthma, COPD, and similar respiratory illnesses. In some cases, mould can even cause fungal infections, such as aspergillosis.
The mould can also damage the sealant itself, causing it to degrade, deteriorate and potentially allowing mould to spread to other areas of the bathroom such as the tiles and grout. Some people claim, online and elsewhere, that it is impossible to stop black mould growing on the silicone seals and the grouting around the tiles. This is nonsense.
In my own – windowless – bathroom, the silicone was resealed in 2019 and it is still providing a prefect seal and preventing water egress. Furthermore, there is still not a single spore of mould on any of the sealant. This is the result of a frequent, thorough, cleaning and, crucially, drying regimen in the bathroom. Using a premium sealant product that provides maximum adhesion and protection is also vital.
However, once the mould is growing thickly in a damp, furry topped and slimy forest – spreading across the bathroom silicone – there are few options. It is now critical to remove the mould as soon as possible and at this point that means removing the silicone. Making sure to remove any remaining pieces of silicone from the surfaces and any mould that has started to grow on secondary areas such as some of the grouting lines, corners, or around the base of taps. Allow the area to dry and if there is still any moisture, dry it off and even leave it for 24 hours if necessary – then apply the new silicone. Always use high quality silicone – even if it costs a little more it will be worth it in the long term. Less mould or even no mould growth, stronger, more flexible silicone seal, easier to clean and much greater longevity.
Once you have cleaned up your bathroom and resealed with quality silicone there are many things you can do to prevent further future outbreaks of mould growth.
The starting point is ventilation, ventilation, and ventilation! Open the bathroom window. If, like me, you do not have a bathroom window then keep the bathroom door open and open the closest window. Dry off the shower screens with dry cloth, towel, or squeegee. Be sure to dry off the edges of bath or shower tray along the silicone seal. A dehumidifier may also help and, although it is not a solution in itself, a good quality dehumidifier is another great tool in the armoury for the battle against the bathroom mould.
If the outbreak of mould growth was very large and extensive and you are concerned about the potential health risks, then it will be necessary to find the cause and source of any dampness or moisture. For this you may need to contact damp and mould specialists who can identify and address any sources of moisture such as hidden leaks or condensation build up that could contribute to further mould growth.
However, if the mould growth had, for example, started on the silicone and spread from that source then there is much you can do without resort to damp and mould experts. Prevention is always better than cure and one of the easiest ways to prevent a return of the mould is a regular cleaning schedule. At least once a week or, if time allows, after every use, clean the bath or shower tray and the walls around them so that there is no build up organic material. Remember to clean and dry off the shower screens too – use a squeegee or dry towel to remove any excess water from them. If you use a shower curtain then you should wash it regularly to remove any build-up of organic materials which the mould will use as a feeding ground before spreading spores further afield.
Mould in the bathroom should never be ignored for both health reasons and in case there is an underlying issue with dampness or hidden leaks that can also cause unseen structural damage. Black mould can be dangerous, particularly for those with existing respiratory issues, the elderly, children, and those with weakened immune systems. Exposure to black mould can trigger allergic reactions, asthma attacks, and respiratory infections so it is extremely important to address any mould growth quickly – with professional help if necessary.
However, it is also worth noting that not all moulds are toxic and not everyone is susceptible. Some moulds do produce harmful mycotoxins but not all moulds are harmful. Some moulds – as Alexander Fleming discovered – are even beneficial. Not every mould, in every bathroom, is the same type and there are still many studies ongoing into the effects of mould and mycotoxins including airborne mycotoxins.
You are always best to focus on prevention – it is much easier than fixing the problem later and your bathroom will look, smell, and feel a much more pleasant place to be. What are the best preventative measures you can apply? Keep your bathroom clean, dry, and well ventilated – even in winter, even in Scotland.