Respiratory hazards

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The following categories describe the main respiratory hazards that may be encountered on site.


Dust is produced when solid materials are broken down into finer particles. Dust may be classed as either inhalable dust (larger dust particles that can enter the airway and may be coughed up) or respirable dusts (that go deep into the lungs and remain there). Generally, the finer the particles are, the more hazardous they are, since they can get deeper into the lungs. The most hazardous dust particles are invisible to the naked eye and stay suspended in the air for long periods.

Nuisance dust has no particular harmful properties but, if inhaled in large enough quantities, can still be harmful and cause breathlessness, wheezing, coughing and irritation.

Operative working with dust suppression to reduce airborne dust

Asbestos fibres in air are responsible for several forms of cancer, including lung cancer and mesothelioma, as well as asbestosis. The microscopic fibres are easily released into the air by disturbing asbestos or asbestos containing materials (ACMs). Asbestos is not easily recognised in materials and is often missed on construction sites. If you suspect you have found asbestos, stop work and tell your supervisor. (For further information refer to Chapter 6 Asbestos.)

Silica dust. Respirable crystalline silica (RCS) are microscopic particles of silica found in many construction materials (such as paving slabs, blocks and kerbs). Being exposed to silica dust for a long time can cause silicosis, lung cancer and other life-changing or life-shortening conditions. Fine silica dust is created when materials are sanded, cut or drilled.

Lead is a toxic metal that can cause many ill health effects (such as mental disturbance, effects on the digestive system, and even coma). Breathing in lead dust is only one of the ways that lead can enter the body. It can also enter by inhaling fumes from vapourised lead, by absorption through the skin from handling lead, and ingestion, via hand to mouth contact, from lead particles on hands when eating or smoking. Lead can be found in many materials used in construction, such as old paint, flashings, roofing materials and some old water and gas pipes.

Wood dust, created by cutting and sanding, is particularly hazardous, causing a range of health effects, from mild irritation (coughing) to sensitisation and certain types of cancer. Softwood dust is known to cause sensitisation (a form of allergic reaction). Hardwood dust is a known cancer-causing agent (a carcinogen) known to be responsible for lung cancer and cancer of the nasal passages. Medium density fibreboard (MDF) is made from separated softwood fibres, hardwood fibres and glues. It can form a particularly fine dust when cut, which increases the likelihood of dangerous amounts being breathed in.

Bird and bat droppings, accumulations of which can be common on construction sites, particularly on demolition or redevelopment projects. Droppings often contain a number of bacterial and fungal biological hazards. If disturbed, they can release a hazardous airborne dust that can result in severe respiratory illness (such as psittacosis) that typically causes flu-like symptoms (fever, headache and muscle aches) but can lead to severe pneumonia and non-respiratory health problems. If work is to be carried out in an area where pigeons, starlings or bats have been gathering or nesting, the area must be thoroughly decontaminated first, and those carrying out the decontamination must wear suitable personal protective equipment (PPE) and respiratory protective equipment (RPE).

Dust is by far the most common hazard on construction sites and in construction work. Silica is the biggest risk to construction workers after asbestos.Heavy and prolonged exposure to RCS can cause lung cancer and other serious respiratory diseases.


Fumes are produced by the heating of metals to high temperatures (such as during welding and gas cutting). Fumes are effectively gases that contain tiny metal particles (molecules) that can be inhaled. Metal fume fever is one of the main illnesses caused by breathing in metal fumes. It is caused by inhaling fumes from the welding or hot working of a number of metals, particularly galvanised steel. It is an acute illness, causing flu-like symptoms.

Vehicle exhaust emissions

Personal carbon monoxide alarm

Vehicle exhaust emissions contain many hazardous substances, including toxic gases and particulates. Carbon monoxide (CO) may cause death quickly, particularly where engines are used or their exhaust gases are discharged into confined spaces where high concentrations of CO gas can build up quickly. Sooty particles from diesel engines are very fine, and can penetrate deep into the lung, causing lung cancer.

Avoiding the use of engine powered equipment (such as disc cutters and generators) in enclosed spaces, spaces with restricted or poor ventilation and confined spaces will reduce the risk. However, where this cannot be avoided, adequate ventilation must be provided and carbon monoxide gas detectors should be used.


Gases are chemicals in their gaseous state at room temperature. They mix with the air we breathe, and may be a simple asphyxiant (such as nitrogen) or toxic (such as hydrogen sulphide).

Hydrogen sulphide (H;S) is given off by rotting organic substances (such as sewage and rotting vegetation). It can build up in poorly ventilated or confined spaces (such as sewers, drains, silos and slurry tanks). H2S smells of rotten eggs and attacks the nerve endings in the nose, disabling them. People think that, if they can no longer smell it, the gas has disappeared, but it is still there and has simply disabled the sense of smell. At some concentrations H;,S can cause unconsciousness within a few breaths, and death in a short space of time.

Other toxic gases that are often found in construction are carbon dioxide and carbon monoxide, although they usually only reach toxic concentrations when released into confined spaces or restricted spaces with poor ventilation.

Carbon dioxide and carbon monoxide are colourless, odourless and tasteless. Both can cause loss of consciousness and death in a short time. Acute exposure to high concentrations of hydrogen sulphide can result in collapse (knockdown), respiratory paralysis, cyanosis, convulsions, coma, cardiac arrhythmias and death within minutes.


Vapours are the gaseous state of substances that are liquids at room temperature. (As fumes can be said to be gases carrying suspended solid particles, vapours can be said to be gases carrying suspended liquid particles.)

Vapours usually form when a substance evaporates (for example, the vapour from glue or paint). Solvents are also used for many different construction processes and can release high levels of vapour.

Vapours can build up quickly in poorly ventilated or confined spaces and can cause headaches, dizziness, collapse and, in rare cases, death. Many vapours are also highly flammable and can be explosive. Long-term exposure to some solvent vapours can also cause chronic health effects (such as liver and lung damage).

Mists and aerosols

Gases and vapours can build up quickly in confined spaces

Mists and aerosols are fine droplets of liquid suspended in air. The droplets are often of respirable size, which means that, if inhaled, they can get deep into the lungs. Some examples of hazardous mists and aerosols are listed below.

Twin pack paints, used for creating high-quality finishes, usually contain isocyanates, which are powerful respiratory sensitisers, as well as being respiratory irritants. They can cause acute symptoms (such as respiratory irritation and bronchitis), but they can also cause asthma if inhaled over a period of time.

Legionella are common bacteria that live in water and watercourses (the aquatic environment). The bacteria are dormant in cold water but thrive and breed in warm, still and stagnant water. In spray or mist form the bacteria are in respirable sized droplets that can easily be inhaled, resulting in legionellosis, which is the name for a group of diseases caused by the legionella bacteria.

The most commonly known of these diseases is probably legionnaires’ disease, which is a potentially fatal form of pneumonia. In construction, water aerosols may arise from dust suppression systems, vehicle washes, hot water storage tanks and sprinkler systems (where the water may be laying still in pipes or tanks for some time).