There have been many published studies linking indoor dampness and mould with illnesses such as asthma and rhinitis. Obvious signs such as visible mould spots on walls or ceilings, damp odours or a history of water damage can point to a higher risk of occupants suffering from an allergenic illness. But how do you know if you’ve been exposed to mould if you’re not seeing any of these classic signs? This post will be looking at other sources of mould exposure. One such study examined the connection between common household risk factors and rhinitis (an inflammation of the nose) and concluded that high humidity was a major factor contributing to above average indoor fungal levels. With over 400 million people suffering from allergic rhinitis annually, there is a need to properly explore practical reasons why and how the built environment contributes to this disorder, and what you can do about it.
The Risk From Domestic Showers
Real estate agents report that many of their wealthier clients’ demand at least two bathrooms for every one bedroom. The main offender that amplifies your mould risk in many homes can be your ensuite bathroom shower. Despite being convenient, hot showers can inadvertently spike humidity levels, not only in the bathroom, but also leading to surface dampness and condensation issues impacting on the adjoining bedroom and walk-in-robe areas if your home has one. This can lead to ideal breeding conditions for yeasts, bacteria and fungal growth and can cause mould to grow on clothing, handbags, suitcases, shoes, curtains and carpets. Now add to this mix, the unwanted spore contamination of indoor air and your bedroom may not be the oasis you thought it was! So how can our DIY mould testing kits help you work out if you might have this silent problem? Well obviously, you can use the swab to reach down into your sink drain and test these areas and see what grows. But you could also swab suspect surfaces as required. In fact, swabbing the environment is catching on. The 'Swab and Send' citizen-science project by the University College, London is being used to raise awareness about antibiotic resistance and help find novel antibiotics. Therefore, this post is premised on providing a practical discussion of how anyone can become intentionally involved in the scientific process by engaging people with data collection and problem solving.
Microbial spores are prime allergens associated with home dampness, mainly due to their microscopic size. When you consider that the average width of human hair is 100-150 microns, compare this with mould spores that are between 3-40 microns in diameter. No wonder this can lead to sneezing, and even worse. Spores can elicit an immune reaction or cause harm through infection or from their mycotoxins.
Domestic shower hoses and faucets can harbour potentially hazardous bacteria, yeasts and fungi. Samples taken during one experiment inside homes revealed a diverse array of fungal pathogens, but in particular, many species of Mycobacteria. This group of microbes have been linked to many illnesses, including cervical lymphadenitis and Chrohn’s disease and typically live in water. The more famous member of this genus is M. tuberculosis complex, which can cause tuberculosis. It is thought that the galvanised protective zinc coating applied to steel or iron shower hoses plus the use of common disinfectants may actively encourage Mycobacterial growth.
Other studies have found large concentrations of Exophiala mesophila which is a microbe causing skin infections. More well-known water-borne pathogens include Legionella which causes a pneumonia-like illness and has been detected inside shower fittings.
These pathogens thrive on a microbial matrix called a biofilm. Biofilms occur when a group of microorganisms form a layer by clumping to each other. Typically, biofilms will cover synthetic surfaces such as the inside of a shower hose or fitting. To survive, the biofilm needs to adhere to this surface. Surface proteins and polysaccharide structures present in biofilms play a part in this adhesion. The risk of illness occurs when pathogens slough off from the biofilm and contaminate the air as an aerosol that can be easily inhaled.
There are a wide range of fungal infections caused by Fusarium species. Superficial infections include keratitis and onychomycosis, allergy and sinusitis and mycotoxin illness as well a more serious co-infections like pneumonia and fungemia in immunocompromised persons. Recent research published in The Journal of Clinical Microbiology (2011) showed that plumbing systems can serve as an important environmental reservoir for human-pathogenic isolates of Fusarium fungus. The research showed using a swabbing method that out of 471 tested drains: 66% of the sinks and 80% of the buildings that were surveyed, tested positive for Fusarium. Further molecular screening of those cultures that grew revealed that the six most common genetic sequences found in the drains were identical to the topmost six genetic sequences associated with human infections.
How Hospital Plumbing Puts Your Health At Risk
It’s not only in domestic households that showers can pose a health risk. It’s a problem seen in hospitals where many patients already have compromised immune systems. Groups who should be concerned include the elderly, people about to have surgery or post-surgery, or those being treated for infections or cancers.
In fact, the drinking water systems used in hospitals have also come under scrutiny. Known methods for disinfecting hospital water sources unfortunately won't kill all the pathogens found inside water pipelines. Bacterial colonies grow in many of the plumbing fixtures of the aptly named: drinking water distribution systems or DWDS. They often form a tolerance to disinfectants and chemical cleaning agents. Biofilm bacteria are 1000 times more resistant to sterilisation than planktonic bacteria. This is one reason why multi-drug resistant bacteria can arise in hospitals.
Remember that pathogen transfer from biofilms is not just from inhaling bacteria in an aerosolised form. Simple touch-transfer can spread bacteria, yeasts and fungi to surfaces and sensitive medical equipment. Think also about other transfer pathways in your home such as from kitchen sink or bench to your smartphone or onto your TV remote! Now isn’t this an interesting set of common yet suspect objects in your home that you could test with our DIY mould testing kits?
The Sink - A Trap For Microorganisms
Sinks are another ideal reservoir for bacterial contamination. Their basic design contributes to unwanted microbial growth. This makes them prime offenders for producing infections. Often plumbing fixtures contain standing water. The P-trap is a typical example. Here a small reservoir of water acts as a physical barrier to prevent off-gassing sewage odour entering the room where the sink is located. Unfortunately, this reservoir creates the perfect humid breeding conditions needed for bacterial colonies to grow. Now add to this the fact that kitchen and toilet water (termed, blackwater) contains oils, greases and fats as well as food wastes and other organic matter. Not to mention the greywater from shower, baths, sinks or your laundry which also introduce organic solids along with skin and hair debris.
But how do the scientists work all this out? If you said: can they make the bugs light up?, then you’d be correct. A recent study was carried out using the green fluorescent protein (GFP)-expressing Escherichia coli to model the dispersion of hospital sink water. The GFP-expressing E. coli wasn’t found to have progressed to the sink basin by running the faucet. In fact, in 14 days, the biofilm had only extended to a level ~4cm above the P-trap.
Only after soy nutrients were added to the P-trap did progression of the GFP-expressing E. coli occur. This was to simulate the impact of blackwater and greywater nutrients. The bacteria eventually reached the sink strainer after seven days. Once the strainer had been colonised, E. coli could then disperse through droplets. These plumes were carried to faucets, worktops and even a Plexiglas shields (again to simulate a splashback), spraying their bacterial load anywhere up to a range of ~75cm. It’s a basic two-step process, transmission of bacteria from the P-trap to the kitchen, lab or bathroom environment occurs in two stages. There must first be the physical presence of bacteria on the strainer or in the sink bowl before droplet dispersal as the second step can arise following growth in a biofilm that extends upwards. Notably, transmission of the GFP-expressing E. coli also occurred along the pipe in the opposite direction downwards and was even able to colonise into neighbouring sinks.
Biofilms can form on the inner surfaces of all pipework and plumbing fixtures. Often these may take several years to grow into a mature, stable community. These biofilms can harbour drug-resistant waterborne bacteria, leading to outbreaks of serious illness. The most common type of bacteria found in the drinking water distribution system is the phylum: Proteobacteria. Gamma-proteobacteria like faecal enteric bacteria, Salmonella or Pseudomonads causing inner ear infections can transfer multi-drug resistant genes to vulnerable people (or patients), causing serious infections. Sink drain pipes are therefore major breeding grounds for such Proteobacterial colonies making our drains of some considerable public health concern.
The size and complexity of these biofilm communities often depends on factors such as pipe age and material. It’s been found that fewer bacteria grow on PVC surfaces than those made from stainless steel or cast iron. Recent research also suggests that iron-reducing bacteria in biofilms might lead to the gradual corrosion of the metal pipes themselves.
One such fungal pathogen that can occur both in shower and sink drains is Fusarium solani species complex 1 (FSSC 1). Better known as a natural rotting agent for gourd fruits like pumpkin, cucumber, watermelon and squash, FSSC 1 can also affect humans. It causes a type of Fusarium keratitis, a fungal disease which in extreme circumstances causes the sufferer to lose sight from the infection. Keratitis is a serious corneal eye infection, which causes a lot of red inflammation and can also be exacerbated by contact lens use. FSSC 1 is found in untreated sewage, but recent studies show that it can be cultivated in biofilms inside all types of pipe surfaces and can easily spread to nearby bottles and solutions used for routine contact lens maintenance.
The Role of Disinfectants
Other recent research has confirmed the central role that contaminated drains and sinks play with regard to the spread of multi-drug resistance in hospitals. Although this study was hospital-based, it highlights the fact that drain cleaning and use of suitable disinfectants are important building maintenance steps. It was recommended in this study (Chapuis et al., 2016) that drains be disinfected using disinfectants based on quaternary ammonium compounds (QACs), or alkyldimethylbenzylammonium chloride (ADBAC) and didecyldimethylammonium chloride (DDAC). It should also be noted that Glucoprotamin based disinfectants are very effective and rapid acting bactericidal and fungicidal agents. To deal with the contaminated drains, the hospital removed all biofilms from sinks and used a bleach solution daily into the drains. Unfortunately, the biofilms did grow back over time, so sinks may need to be dismantled to gain access to drains for periodic cleaning. One can extrapolate from this study to other drainage systems like showers and toilets.
It’s interesting to rank those areas of the home that have been found to be the most contaminated with toxic bacteria like total coliforms and faecal coliforms that cause food poisoning. Unsurprisingly, the kitchen was found to be most contaminated with the sponge dishcloths and kitchen sink and being the worst coming in first and second place respectively. The third most contaminated area of the home was then the bath sink drain, followed by faucet handles, the bathroom countertop and then the bathroom floor. Of those surfaces that were swab tested, the least contaminated surface was found to be the toilet seat. The research showed that hypochlorite (bleach) containing disinfectants needed to be used more than once with the authors describing that the introduction of hypochlorite cleaning products into the home results in a significant reduction in bacteria in most cases, but that a combination of different cleaning products combined with regular use was the only way to achieve significant reductions.
This is all well and good, but for some people, the use of cleaning products based on hypochlorite, ammonia or hydrochloric acid can cause asthma and lower respiratory tract symptoms. This article is not meant as a review of different disinfectants, but other cleaning agents based on peracetic acid and vinegar have been shown to be effective in different contexts. For example, in a dental context, commercially available vinegar (acetic acid) was compared against 10% formalin, 3% hydrogen peroxide, 5.25% sodium hypochlorite, 70% alcohol and boiling in water at 100ºC for 20 mins. All treatments were successful except for the sodium hypochlorite and alcohol disinfectants. Other research from Sweden looking at practical methods to remove biofilms from drains used 24% acetic acid solution with impressive results. This shows that different cleaning compounds have different abilities, so there is some consumer choice here that can allows for personal preferences and yet still provide a cleaning agent that can perform useful chemical work.
A word of caution is also necessary, since there are many drain cleaners in the market and concentrated acid solutions are unfortunately a leading cause of burns in children and adults. Caution should be exercised when using such products. At the other end of the spectrum, one approach to making water clean is to actively filter it using for example a reverse osmosis system. These have been shown to remove viable yeasts, bacteria and fungi from the water supply and can be fitted by your plumber.
Vigilance is recommended and one should not overlook drains for their contribution to yeasts and mould growth as well as pathogenic bacteria. DIY mould testing kits can be used to swab inside drains and can help you visualize the fungal load inside shower heads and drains in sinks and bathrooms as a hygiene monitoring step. Notably, drain swabbing has been used since the 1970's for the assessment of food poisoning bacteria and is a hallmark of routine surveillance in food processing environments and hygiene monitoring. As we learn more about the role of microbes in biofilms and how these develop within buildings, the relationship between identification of often overlooked reservoirs - for example the black yeast biofilms, and how these may lead to unwanted infections like those from Fusarium and other fungi are likely to be increasingly discovered. There are many different types of swabs and nutrient formulas used to selectively culture different microbes. However, this blog post isn't meant to be an exhaustive review of different isolation methods, but suffice to say, my premise is to introduce you to the 'citizen science' approach, that's a fast-track way to begin mapping your own personal indoor microbiome.
I’m sure next time you step inside your shower, you’ll think about this article and look at your shower head and sink and wonder what’s growing inside? Although water is vital to life - if the standard methods of transporting water are endangering our health, we might need to think again about the mechanics of the process. Who would have thought that hidden pathogens stuck deep in biofilms inside the plumbing of our homes (and hospitals) is prompting engineers and scientists to overhaul the design of our plumbing systems. What disruptive new technologies can you think of for dealing with biofilms inside our drains, sinks and pipes?
It's also easy to dismiss the topic of drains and their connection with human illness, by reactively thinking that just because it's a dirty environment anyway, that it's not likely to harm you! This response is an interesting example of unconscious selective attention and happens when we edit things out of our environment, and give unequal attention to some things whilst ignoring other things. Thinking about infection control and then using mould test kits to proactively measure the contamination levels inside our drains is a sensible step towards a healthy home and a great exercise in environmental citizen science.
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