ABC of Work Related Disorders: BUILDING RELATED ILLNESSES
BMJ 1996; 313 doi: https://doi.org/10.1136/bmj.313.7058.674 (Published 14 September 1996) Cite this as: BMJ 1996;313:674
- P H Appleby
- Paul Appleby is divisional director of Building Health and Safety, a division of Thorburn Colquhoun, London.
The idea that buildings can make people ill is one that undermines deep seated beliefs in the function of buildings. Buildings are supposed to provide shelter and a safe environment where people are protected from the elements. The idea of illness associated with manufacturing or mineral extraction is reasonably well understood. However, people becoming ill because of exposure to some unseen agent in their home, school, or office can create a panic out of proportion to the risk.
Building related illnesses fall into two categories: those that have an identifiable cause—such as legionellosis, humidifier fever, and conditions resulting from exposure to known substances such as asbestos, lead in paint, formaldehyde, etc—and those that have no readily identifiable cause but can be described only by a group of symptoms known as sick building syndrome.
Algal growth on drift eliminators of a building's cooling tower—a potential source of pollutants.
Sick building syndrome
The term sick building syndrome is used to describe a situation in a building where more people than normal suffer from various symptoms or feel unwell for no apparent reason. The symptoms tend to increase in severity with the time that people spend in the building and to steadily improve or disappear when people are away from the building.
Symptoms
The symptoms associated with sick building syndrome are those associated with common illnesses and allergies, usually in a relatively mild form so that many sufferers may not see a doctor and may not take time off work.
Symptoms associated with sick building syndrome
Eyes—irritated, itching, dry, watering
Nose—irritated, itching, runny, dry, blocked
Throat—sore, constricted, dry mouth
Head—headache, lethargy, irritability, difficulty in concentrating
Skin—dryness, itching, irritation, rashes
Causes
There is no single known cause of sick building syndrome, but there are several risk factors that have been identified from a large number of studies on the epidemiology of the syndrome and investigations of “sick” buildings.
It is evident that some of these factors may combine to cause particular symptoms. For example, eye symptoms may be caused by a combination of long term use of a display screen, low humidity, airborne dust, and irritating airborne solvents.
The increase in use of computers seems to have been a major contributing factor to the onset of sick building syndrome. The additional heat load has led to either overheating or the installation of air conditioning, while the nature of working at a display screen has not only created eye problems but also headaches and musculoskeletal symptoms.
Risk factors for sick building syndrome
Characteristics of work and building
Sedentary occupation, clerical work
More than half of occupants using display screen equipment for more than 5 hours a day
Maintenance problems identified
Low ceilings—typically lower than 2.4 m
Many changes or movements of furniture and equipment
Public sector tenant or occupant
Large areas of open shelving and exposed paper
Sealed building and city centre location
Large size—typically an occupied floor area greater than 2000 m2
Centralised control of environmental conditions—no local control of heating, ventilation, etc
Building more than 15 years old
Scruffy appearance
Large areas of soft furnishings, carpets, and fabrics
Environmental factors
Low room humidities
Low supply rate of outdoor air
Smoking permitted in work areas
Damp areas and mould growth
Dust, solvents, and ozone emissions from printers and photocopiers
Low frequency fluorescent lamps creating subliminal flicker
High room temperatures
Excessive supply rate of outdoor air
Dusty atmosphere
Gaseous emissions (volatile organic compounds) from building materials and cleaning products
Low frequency noise
Criteria covered by Health and Safety (Display Screen Equipment)
Regulations 1992
Daily work routine of users
Eye tests
Provision for training and information
Risk assessment and analysis of workstations
Requirements for workstations
Display screen Keyboard
Work desk Work chair
Task design Software
Environment—heat and noise
Concern about display screens resulted in a European Commission directive. In Britain this was enacted under the Health and Safety (Display Screen Equipment) Regulations 1992, which requires all users to be trained and provided with certain facilities. From January 1997 all workstations which include a display screen will have to meet the criteria.
Types of building affected
Sick building syndrome not only occurs among office workers. It has been identified in schools, nurseries, libraries, and apartment buildings.
Investigating sick building syndrome
An “outbreak” of sick building syndrome may not be obvious. It may come to light because of complaints to personnel, building maintenance, or occupational health departments rather than to general practitioners.
The Health and Safety Executive have produced the pamphlet How to deal with sick building syndrome—Guidance for employers, building owners and building managers. This gives a useful guide to the steps that should be taken before calling in a professional investigator.
Steps in investigating a suspected outbreak of sick building syndrome
Check for local flu or cold epidemic
Check for breakdown of air conditioning or ventilation system
Check for major pollution sources, both indoors and outdoors
If there is nothing obvious then
Check with staff for nature and extent of symptoms and complaints
Check absenteeism records
Check maintenance history
If action on the above does not alleviate the problem then
Review design, operation, control, and maintenance of heating, ventilation, and air conditioning and check against original design specifications
Check whether changes in layout of partitions and space and use of building have interfered with operation of heating, ventilation, and air conditioning
Check organisation of work and management practices
If necessary specialist advice should be sought on further investigations
The Royal Society of Health has designed a questionnaire for this purpose, published by the Building Research Establishment.
Problems with indoor air
Concentrations of pollutants in non-industrial buildings are generally orders of magnitude below published limits for occupational exposure. Air quality is rarely a problem in the absence of other factors that contribute to the symptoms which make up sick building syndrome. Exceptions can occur, however, when there are unusual sources of pollution or inadequate ventilation.
Larger dust particles in outdoor air should be removed by filters in a building's central air handling plant, which supplies treated air to the building. If these filters are neglected, however, they can become overloaded or disintegrate and provide a source of pollution. If the filters are ineffective, dust will coat the inside of the heating and cooling coils, fans, silencers, and duct work. Where moisture is present, such as in cooling coils that take moisture out of the air, a sludge can form and growth of mould is possible. Dirty air handling systems can also generate odours, which are distributed throughout the building.
Common indoor air pollutants and their sources
Tobacco smoke
Ozone
Source: Photocopiers and printers
Volatile organic compounds
Source: Carpets, furniture, building materials, paints, cleaning agents
Dusts
Source: Outdoor air, skin, paper, printer and photocopy toner, mineral and glass fibre
Carbon monoxide
Source: Traffic, combustion (such as gas cookers), tobacco smoking
Oxides of nitrogen
Source: Traffic, combustion (such as gas cookers)
Isocyanates—Toluene, diphenylmethane, hexamethylene, naphthalene
Typical indoor concentration: 50-103 μg/m3 (trace outdoors)
Possible sources: Adhesives, sealants, environmental tobacco smoke, wall and floor coverings, paint, moth crystals (naphthalene)
Formaldehyde
Typical indoor concentration: 0-0.6 ppm (0-0.03 ppm outdoors)
Possible sources: Urea formaldehyde foam insulation, fabrics, carpets, environmental tobacco smoke, floor and wall coverings, adhesives, sealants, lacquer, plywood, chipboard, gypsum board, disinfectants
Allergies
Most airborne allergens (aeroallergens) are organic particles with a mean mass aerodynamic diameter of less than 10 μm. Some are aerosols or vapours.
An allergen's size dictates where it lodges in the airways: smaller particles penetrate the alveoli and cause alveolitis, those of 5-30 μm size tend to lodge in the bronchi and may induce bronchospasm, while larger particles lodge in the nose and give sensitised people rhinitis. Particles that lodge in the eyes may cause conjunctivitis. Allergens of small size, such as some chemicals, may combine with human proteins to cause allergic reactions.
The concentration of allergens in most homes is usually much higher than in offices, particularly in older houses with gardens and pets. House dust mites thrive in mattresses, while moulds grow in gardens, bathrooms, etc.
Airborne allergens in the workplace
House dust mite excreta
Typical indoor concentration: 0-60 mites/g dust
Possible sources: Carpets, upholstery
Fungal spores—Penicillium, Cladosporium, Aspergillus, Alternaria,
Trichoderma, Stemphylium, Mucor
Typical indoor concentration: 10-103 spores/m3 (104 spores/m3 outdoors)
Possible sources: Damp surfaces
Di-isocyanates—Hexamethylene di-isocyanate (HDI), toluylene di-isocyanate
(TDI), 4:4'-di-isocyanate-diphenyl methane (MDI)
Possible sources: Urethane foams
Phthalate anhydrides
Possible sources: Epoxy resins
Natural resins
Possible sources: Timber
Enzymes
Possible sources: Biological detergents
Insect detritus
Animal proteins
Exposure to chemicals may be greater in newly decorated and furnished offices, although formaldehyde has been largely phased out by furniture and fabric manufacturers in Britain. The forced movement of air in air conditioned and ventilated buildings may encourage circulation of mould spores and other allergens, especially if they are present within the air handling system itself. Some poorly maintained air handling systems may experience mould growth in filters and humidifiers, although excessive growth is rare.
Action plan to improve air quality in buildings
Use materials with components of low volatility and low toxicity
Allow new carpets and soft furnishings to lose most of their volatile component before occupation by workforce
Minimise use of fibrous materials for finishes and maximise use of wipeable surfaces
Provide enclosed storage for files, books, and papers
Ensure there is no penetration by rain or condensation problems
Ensure that plaster, concrete, etc, has dried out thoroughly before occupation
Use photocopiers and laser printers with integral devices to reduce ozone production
Consider banning smoking in work areas
Isolate dirty and malodorous processes and areas from working or living areas and keep them under negative pressure
Locate air inlets away from roads and other sources of pollution
Fit air conditioning and ventilation supplies with high efficiency filters
Do not allow filters to become too dirty or dirty air to bypass them
Keep inside of air handling system clean
Humidifier fever
Actinomycetes are filamentous bacteria which resemble fungi in form and in the types of disease they produce. Thermophilic actinomycetes have been implicated in outbreaks of extrinsic allergic alveolitis such as farmer's lung and mushroom worker's lung, as well as the form of allergic alveolitis called humidifier fever.
A spray humidifier consists of a network of pipes mounted across the airstream. The pipes contain spray nozzles and are connected to a pump which draws water from a tank or pond beneath and through which water is recirculated.
Outbreaks of humidifier fever are rare but generally dramatic when associated with heavily contaminated spray humidifiers or air washers. Occasionally, spray humidifiers have been used to wash out particulates from the air in place of filters. This creates a large volume of sludge which forms in the pond and on downwind surfaces. This sludge can provide the nutrients for microbiological growth.
Internal view of spray humidifier in air supply to a building.
Legionellosis
Legionellosis is a generic term which describes Legionnaires' disease and Pontiac fever. These are relatively uncommon infections, with about 200 cases reported annually in England and Wales, although the reporting rate is thought to be only 10% because the symptoms can be mistaken for other types of pneumonia. These diseases are caused by inhalation of water droplets or particles containing motile thermophilic bacteria of the family Legionellaceae, of which there are some 40 species. The one most commonly associated with Legionnaires' disease is Legionella pneumophila serogroup 1, there being 14 serogroups. L pneumophila has also been implicated in flu-like illnesses which have been named after the places where they were first reported—that is, Pontiac fever and Lochgoilhead fever.
Small, rod shaped bacteria of Legionella pneumophila in culture from lung tissue.
These bacteria are small and rod shaped and penetrate deep into the alveoli, where they cause infection. There is an incubation period of two to 10 days before the symptoms appear, and it is thought that only 1% of those exposed develop symptoms. The symptoms of Pontiac fever may develop after only five hours or up to three days after exposure.
Although legionella bacteria are found in nature, they tend not to become a problem unless they enter building water systems, which create an aerosol that can be inhaled by susceptible people and which provide a suitable niche for the multiplication of the bacteria
In its most severe form Legionnaires' disease is a pneumonia that can be fatal or leave the patient debilitated if it is not treated in time. Initial symptoms include high fever, chills, headache, and muscle pain. A dry cough soon develops, and most patients experience difficulty with breathing. Patients may also develop diarrhoea and vomiting and become confused and delirious.
Systems and equipment which can be a source of legionellosis
Evaporative cooling towers and condensers
Spray humidifiers and nebulisers
Hot and cold water systems serving taps and showers
Spa baths and whirlpools
Horticultural misting systems
Car washes and lances
Lathe coolant systems
Prevention
Where there is a risk of legionellosis steps should be taken to ensure that equipment and systems are kept as clean as possible and regularly disinfected. If possible, water temperatures should be kept either below 20°C or above 50°C. If this is not possible biocides should be added to the water to prevent legionella bacteria multiplying, provided the biocides cannot enter the indoor air; thus, ongoing treatment of water is not possible with hot and cold water systems or spray humidifiers.
Risk factors in outbreaks of legionellosis
Water temperature between 20°C and 50°C
Nutrients available for growth, such as proteins and rust
Niches which will protect Legionella from heat and biocides, such as limescale and sludge
Fine (invisible) aerosol such as that generated from taps, shower heads, cooling towers, and spray humidifiers
Low water turnover—temperature may rise, biocides decay, and sediment precipitate to form a sludge
Open to ingress of animals, insects, dirt, and sun—direct sunlight encourages algal growth
Susceptible people exposed to aerosol—for example, those with impaired lung capacity or immune system
Guidance on the design and maintenance of these systems is given in the Health and Safety Executive's guidance note The prevention and control of legionellosis.
Recommended further reading
Health and Safety Executive. How to deal with SBS—Guidance for employers, building owners and building managers. London: HMSO, 1995.
Chartered Institution of Building Services Engineers. Healthy workplaces. Balham: CIBSE, 1993. (CIBSE GN2:1993.)
Health and Safety Executive. Display screen equipment work. London: HMSO, 1992.
Health and Safety Executive. The prevention and control of legionellosis. London: HMSO, 1991. (HS(G)70:1993.)
The ABC of Work Related Disorders is edited by David Snashall, clinical director of Occupational Health Services, Guy's and St Thomas's Hospitals NHS Trust, London.