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Sick Building Syndrome
Public concern and awareness has grown over the last few decades about adverse health effects of exposure to chemicals in the everyday environment. Much work has focused on potential chemical exposure in the work environment in offices. This first came to consideration in the 1970’s when reports linked symptoms to the occupancy of buildings that had been deliberately “air-tightened” to conserve energy during a Middle East oil embargo. In the 1980’s, the World Health Organisation (WHO) recognised the issue and described the situation of “symptoms with increased frequency in buildings with indoor climate problems”. These symptoms included irritation of the eyes, nose and throat, dry mucous membranes, dry skin, headaches, frequent nasal symptoms, breathing difficulties, abnormal taste sensation, distorted sense of smell, tiredness, dizziness, lack of concentration and nausea.
These symptoms, when they arise in relationship to being in a particular building and there is a consistent pattern of occurrence in that environment and freedom from problems away from the building, raises the potential for the diagnosis of sick-building syndrome (SBS). This would be supported by the presence of colleagues within the same environment also experiencing such symptoms with the same temporal pattern. The diagnosis of SBS also requires the exclusion of symptoms arising due to allergies to mould and dust within the building and the presence of infection such as sinusitis, or outbreaks of more severe infection such as Legionnaire’s disease or tuberculosis for example. If skin problems predominate then these could be caused by allergy, by contact sensitivity with certain office plants or by an irritant response to fibreglass. These possibilities need to be considered and excluded before reaching a diagnosis of SBS which arises due to exposure to low levels contaminants within the air.
There is no single environmental factor or group of factors that have been established as a single cause of SBS. A list of common contaminants in indoor air is shown in Table I and it can be seen that contaminants in ventilated buildings range from potentially fatal bacteria, such as for Legionnaires disease outbreaks, to more commonly volatile organic compounds omitted from pressed wood furniture manufactured for example, from MDF or as emissions from printers and photocopiers.
The adverse exposure to these factors is more likely if there is uneven or inadequate ventilation within the building environment. Ventilation is usually controlled by heating, ventilation and air-conditioning (HVAC) units that draw air in from the outside, condition that air with respect to temperature and humidity, with the aid of the outgoing air, and then circulate that incoming air within the building. It is recommended that there is 20 cubic feet per mm (0.57 m3/min) of outside air per occupant of building ventilation. Whilst designs in new buildings should be correct, it is clear that on-going changes could influence the ventilatory adequacy, through for example, environmental changes affecting the air intake, such as environmental pollution or loading bay exhaust, depending on the sighting of the intake vent, and changes within the building, such as the number of occupants or the internal structural and furniture arrangements. Although overall ventilation may appear adequate, ventilation in different parts of the building may be uneven or, because of the internal layout, fresh air from the supply may be short circulated to return to the ducts thereby by-passing the occupants breathing zone. Such local factors may account for symptoms only arising in selected individuals and may be more common in persons resident for work in one environment, where they may have more prolonged exposure, as compared to another individual who has responsibilities in several different areas and is not exposed for such a prolonged period to air in any one place within the building. Regional changes in air temperature, air humidity (e.g. too dry), lighting and air velocity may all be important determinants of SBS.
The individual’s response to the building air is also an important determinant of the expression of symptoms, in addition to the quality of the air. Studies have shown that SBS is more common in individuals with work related stress, poor job satisfaction and low job status. The diagnosis of SBS is based on the patient’s clinical presentation, the presence of similar symptoms in co-workers, improvement in symptoms away from the building and the absence of any other likely diagnosis. If such a diagnosis is considered probable, then there should be an indoor-air quality evaluation of the building. Remedial action for the building will depend upon this evaluation.
Table 1 - Common contaminants in indoor air
Volatile Organic Compounds: Dust/Fibres: Bio-aerosols: Entrapped Outdoor Sources: Contaminants generated by human activity: Physical factors: Others: |
Author: Dr Peter Howarth, Southampton, UK - March 2006