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Despite numerous investigations, no single cause has actually been established for sick building syndrome. Various experts have different theories:
One theory suggests that chemicals travelling in the air enter the nose and affect an area of the brain called the limbic system. The limbic system plays a role in emotions, motivated behaviour, and memory, which may make a person more sensitive to a chemical odour it previously encountered.
Another theory suggests that the immune system is somehow damaged.
Still another theory, called "toxic-induced loss of tolerance", suggests that acute or chronic exposure to chemicals causes some susceptible people to lose their tolerance for chemicals they previously could tolerate.
Other theories posit that fungi are primarily to blame, or that physical factors such as humidity, temperature, lighting, or the air-conditioning system are the cause.
None of these theories are proven but what is certain is that symptoms are more common in buildings with air-conditioning or mechanical ventilation. Six building features are strongly associated with symptoms of sick building syndrome (McIntyre and Sterling 1982):
The following table summarises the types of problem found by the National Institute for Occupational Safety and Health (a US government organisation) in a study of 203 indoor air quality investigations:
||18||Exposure to chemical or other toxic agent generated within the office space, e.g. methyl alcohol from spirit duplicator, methacrylate from a copier, sulphur dioxide from a heating system, amines used in a humidification system, chlordane used as a pesticide|
|21||10||Exposure to a chemical or other toxic substance originating from a source outside the building, e.g. motor vehicle exhaust fumes, construction activity, underground petrol spillage|
|7||3||Problems from the material used to construct the building (figure excludes asbestos), e.g. formaldehyde, fibreglass|
||98||48||Symptoms may be due to low levels of multiple contaminants and/or poor ventilation|
|6||3||Problems due to a reaction to micro-organisms in the building environment|