Introduction to Chemical Hazards
The effect of such a substance may occur immediately, or it may not manifest itself for a period of time. The hazard associated with a chemical depends on:
- The type of chemical substance.
- Other chemicals that may be mixed with it, if any.
- The derivatives that may be produced through physical or chemical processes and operations.
- The relative proportion of the chemical, if it is in a mixture or solution with other substances and chemicals.
Effects of Chemical Hazards
Exposure to hazardous substances which result in rapidly developing adverse health effects are referred to as acute toxic effects. In most cases acute effects will generally tend to only last a short duration.
Symptoms of acute toxic effects vary. They include immediate eye and respiratory tract irritation from exposure to ammonia, burns to the skin caused by direct contact with strong acids or alkalis or narcosis from exposure to organic solvents.
Long latency diseases are often referred to as chronic health effects. These tend to occur after long-term, repeated exposure to lower levels of a hazardous substance. Chronic or long-term effects are long lasting and develop gradually over long periods of exposure, usually months or years. Recovery once exposure stops is extremely slow and often incomplete; in fact, the effects are often permanent. Chronic effects include cancer, bronchitis, and dermatitis.
Forms of hazardous substances
Hazardous substances occur in many physical forms. Knowledge of these is essential in understanding routes of entry into the human body, typical exposure scenarios and determining appropriate controls.
There are different physical forms in which the hazardous substances may occur
- Gas - a formless fluid that completely occupies the space of any enclosure. Examples include oxygen nitrogen and carbon dioxide.
- Vapour - the gaseous phase of a material normally liquid or solid at normal temperatures and pressures.
- Aerosol - a dispersion of particles of microscopic size in air, these may be solid particles (dust, fume, fibre) or liquid particles (mist).
- Dust - airborne solid particles that range in size from 0.1 - 100µm in diameter. Examples include wood dust from cutting and sanding operations and quartz dust from crushing of rocks.
- Fume - airborne solid particles generated by condensation from the gaseous state. Examples include fume from high temperature cutting or welding of metals.
- Mist - airborne liquid droplets generated by condensation. Examples are oil mist and paint spray mist.
- Fibre - a thin and greatly elongated solid substance. Examples include asbestos and glass fibres.
Hazardous substances have four possible routes of entry into the human body in the workplace
- Inhalation - inhaled via the lungs and respiratory system.
- Direct contact - absorbed via the skin and eyes and mucous membranes.
- Ingestion - swallowed and enters the gastrointestinal tract.
- Injection - direct puncture of the skin by contaminated equipment or through open wounds.
Examples of Chemical Hazards in Rail
Lead is widely used in metal products, sheet metal, solders, and pigments. Lead is readily absorbed through the lungs, therefore exposure to lead and inorganic lead compounds usually occurs through inhalation of dust and fume from metal processing, grinding, and welding. In the rail industry, simple processes such as painted bridges (where the paint can potentially contain lead) can contribute to worker exposure.
Possible health effects include:
- fertility issues
- abdominal pains
- muscular weakness
- Kidney damage
- possible nerve and brain damage.
Asbestos is the term for a group of naturally occurring silicate minerals. These have proved commercially useful due to properties such its tensile strength, chemical resistance, flexibility, non-combustibility and good thermal and electrical insulation.
Due to these benefits asbestos was widely used in a variety of forms and products in both home and industrial environments. It can be found in a variety of application and locations in buildings built before 1980 and any work on building such as these may need to consider the presence of asbestos.
Possible health effects:
- Asbestosis - exposure to large amounts, normally over many years. The presence of asbestos fibres in the lungs lead to the formation of scar tissue or fibrosis resulting in a loss of elasticity and lung function.
- Lung Cancer - increased risk of lung cancer in people who smoke and are exposed to asbestos.
- Mesothelioma - a malignant growth in the lining of the lungs which may develop any time from 15 to 50 years after the first exposure to asbestos.
Respirable Crystalline Silica (RCS)
Silica is a natural substance found in most rocks, sand, and clay and in products such as bricks and concrete. In the workplace these materials create fine dust called respirable crystalline silica (RCS) when they are cut, sanded, carved etc. RCS can be inhaled and cause harm to your health. A major component of ballast dust is RCS which may be liberated into a workplace atmosphere dependant on the operation.
RCS appears on Health and Safety Executive top ten list of occupational carcinogens which should be prioritised for future intervention.
Possible health effects:
- Silicosis - results in increased breathing difficulties and can increase the risk of infections within the respiratory system. There is an increased risk of lung cancer.
- Chronic obstructive pulmonary disease (COPD) - a group of lung diseases resulting in severe breathlessness, prolonged coughing, chronic disability which in some cases will be fatal.
- Lung cancer - prolonged exposure to RCS can cause lung cancer.
Welding is an integral part of the fabrication and maintenance activities found within the rail industry. Welding can liberate a variety of hazardous materials within the workplace environment, these include:
- The metal being welded, the metal in the filler rod or constituents of various types of steel (e.g., nickel or chromium)
- Any metallic coating on the article being welded (e.g., zinc and cadmium on plated metals)
- Any paint, grease or dirt on the article being welded (e.g., Lead, carbon monoxide, carbon dioxide and other irritant breakdown products)
- Flux coating on the filler rod (e.g., inorganic fluoride)
- Action of heat or ultraviolet light on the surrounding air (e.g., nitrogen dioxide, ozone)
- Inert gas used as a shield (e.g., carbon dioxide, helium, argon)
- Fume and dusts created from pre and post weld dressing activities.
Acute health effects:
- Irritation to the throat and airways in the lungs - welding fume can cause dryness of the throat, coughing or tightness in the chest.
- Acute irritant-induced asthma - high levels of exposure can cause asthma, but this is not common.
- Metal fume fever - flu-like symptoms after welding usually linked to welding or hot work on galvanised metals. High exposures to mild steel weld fume can also cause this illness.
- Acute pneumonia - welders are particularly prone to a lung infection that can lead to severe and sometimes fatal pneumonia.
Chronic health effects:
- Lung cancer - increased risk of lung cancer from exposure to all welding fumes and may cause kidney cancer.
- Chronic obstructive pulmonary disease (COPD) - may be a causative factor towards COPD where lung function can decline more quickly than expected. If the illness progresses, workers can become very severely incapacitated.
- Welder's lung - deposition or metal particulate in the lung considered to be a benign type of pneumoconiosis. But if an individual also suffers with COPD symptoms can be made worse.
- Occupational asthma - Occupational asthma can be caused by specific metals in the welding fume. Sufferers can also develop a short-term temporary reduction in lung function.
Other health effects:
- Skin effects
- Neurological effects
- Ocular melanoma
- Arc Eye
Diesel engine exhaust emissions
Diesel engine exhaust emissions (DEEE) are defined as a complex mixture of gases, vapours, liquid aerosols, and particles created by burning diesel fuels. They are created from the burning of diesel fumes within an internal combustion engine.
DEEE may contain over 10 times the amount of soot (carbon) particles than in petrol exhaust fumes. The International Agency for Research on Cancer (IARC), part of the World Health Organization, has defined DEEE as a Group 1 carcinogen, so these emissions are treated as a definite cause of cancer. The IARC has estimated that regular exposure to DEEE at work can increase the likelihood of developing lung cancer by up to 40%.
Individuals who work with or near diesel-powered equipment or vehicles can be affected, such as forklifts, lorries, buses, trains, and tractors. This is particularly so in enclosed spaces like garages or workshops. Operators who also work with fixed power generation systems such as compressors, generators, or power plants.
When considering exposure to DEEE we must not only consider it as a singular material but also as its constituent materials which can also have a variety of health effects dependant on amount found.
Acute health effects:
- Irritation - to the nose, eyes and respiratory tract from short term high exposure levels.
Chronic health effects:
- Respiratory ill health
- Lung cancer
- Bladder cancer (limited evidence).