Our Systems and Products:Microbiological pollutants
It is generally accepted microbiological pollutants are increasing in buildings and have an increasing negative impact on human health. Microbiological refers to dust mites and their faeces, pet allergens, pollen, moulds, fungi, bacteria and viruses. Some of these such as pet allergens, pollens and some bacteria, viruses and moulds are introduced by occupants or are brought in from the outside. However many are a result of the built environment itself, and in the main are due to environmental conditions of humidity and temperature which have only been experienced in buildings in the very recent past.
The relationship between relative humidity and microbiological pollutants in buildings is well established through what we know about the ability of bacteria, viruses, moulds, mites etc to thrive in different conditions. Basically all the pathological organisms require very high or (more rarely) very low levels of humidity to thrive. They cannot thrive, and in many cases cannot even survive, if relative humidity is kept between 40% and 60%, at best at around 50%.
In addition other chemical reactions such as those involving VOCs, are more dangerous to the human body as humidity levels rise, particularly at levels over 70% RH. At levels under 40% human mucus membranes become dry and more vulnerable to irritation from chemical pollutants and small particles. People become much more sensitive to odours at low RH levels, and people wearing contact lenses can suffer bad irritation. At levels of under 35% RH the effect of static on the human body is also considerable both internally and externally. For example external static shocks from walking on nylon carpets can be as high as 35,000 volts at low RH levels. Increasing RH to above 35% would automatically reduce the potential of static shock to 1,500 volts or less.
The levels of relative humidity in buildings are therefore crucial to human health. This is illustrated in the graph below.
Reproduced with permission of www.humidic.dk
Microbiological pollutants are therefore linked intrinsically by their biology to humidity. This is mainly a result of built environment conditions. This is a very serious issue, and it is no exaggeration to say that conditions of the built environment can cause illness and death. This is now proved in court of law both in the UK and elsewhere .
The common diseases which are a result of high levels of microbiological pollutants are particularly auto-immune diseases and allergic reactions such as asthma. Asthma is of particular concern because the UK has the highest rate of asthma in the world, being 1 in 6 of the population. In Scotland this rate is even higher. Disturbingly, the incidence of the disease is far higher among the young and appears to be increasing continually (among 13-14 year olds the rate is 35% and among 5-6 year olds the rate is 41% ). In the UK almost 1500 people die every year from asthma attacks and there are about 74,000 emergency hospital admissions. The cost to the state and individuals is over a billion pounds, and is growing. And yet a few decades ago this situation did not exist. Asthma levels were very low and had remained constant for hundreds of years in the UK (and indeed elsewhere in the world) until the 1970s. Asthma levels only started rising exponentially in the mid 1970s as buildings began to be insulated and draught proofed as a result of the introduction of energy efficiency measures and legislation.
The link between high levels of humidity and asthma is the dust mite, the faeces of which contain 15 known allergens which can cause asthmatic symptoms. Dust mites can only thrive in relative humidities of over 70% . At a relative humidity of 80% and temperatures of 20°C -30°C the mites find their ideal breeding conditions and can rapidly reach epidemic proportions. On the other hand at less than 60% it is not possible for them to digest the human skin on which they live, or to reproduce.
There is now therefore an accepted and straightforward relationship between asthmatic symptoms, dust mite levels and high relative humidity. This has been proven in practice by a number of actual studies undertaken where by clearing dust mite faeces from the bedding, carpets etc, and then reducing levels of relative humidity by ventilation systems has led to the longterm disappearance of dustmite infestation and at the same time to the significant improvement of occupants asthmatic symptoms. In a recent study it was found that the cost of doing this (£2000) in houses with bad asthma sufferers had a pay back period in medical costs of 18 months – ie the improvement to the health of the individuals involved was such that £2000 was saved in medication, doctors time and emergency admissions to hospital in this period over the average costs of similar asthmatics in a similar period.
The causal chain between asthma, dustmite and the relative humidity of buildings is fairly simple. The effect of other microbiological pollutants is more complex but potentially just as serious. Suffice to say for now that there is also a straightforward connection between virtually all moulds, fungi, bacteria insects etc and relative humidity in buildings, as is well known by building conservationists. The environmental control of building pathologies is an established science used widely in historic buildings, museums, archives and libraries. The moulds fungi, bacteria etc which attack building fabric and material objects require exactly the same conditions to thrive as those organisms which attack human health. The levels of moulds in building is a particular concern in the USA and has led to a number of high profile cases around moulds such as Stachybotorus Chartarum, supposedly linked to autoimmune problems such as cancer. This has subsequently been investigated in the UK by Fugenex for the RICS, with the alarming conclusion that it was present in 25% of all buildings where mould was detected. Furthermore in a similar conclusion to Stirling Howieson’s work on asthma, it was found that the worst kind of building for infestation was the modern middle class house, and that the worst place within that house was the bedroom. Fugenex reported that this was due to “trapped moisture”, and Stirling Howieson confirms that high levels of Relative Humidity are the cause of this problem. Bedrooms in modern houses are typically above or next to bathrooms, have little ventilation and are non-breathing structures with cold bridges, thus encouraging mould and high RH. In one case studied by Stirling Howieson, the consequence of this was that 25% of the weight of the pillow was dust mite faeces or dead dustmites. It is ironic or perhaps sad that the bedroom should be the least healthy place in the house, as it is the place that people go when needing rest, or when they are ill.