Chemical substances
A great many chemical substances are used in construction – there is hardly a site without them. They are found in adhesives, cleaning agents for brickwork and stonework, decorative/protective treatments for timber and metals, floor treatments, fungicides, cement and grouts, insulants, sealants, paints, solvents and much else. Of particular importance are solvents, which are liquids commonly used in paint strippers, lacquers, varnishes, surface coatings, thinners and similar cleaning materials.
Chemicals and their risks
Many chemicals are hazardous, with a potential for fire and explosion, or toxic, with an inherent potential to cause poisoning. Toxic substances cause both acute effects, such as dizziness, vomiting and headaches, produced in a short time by exposure to solvents, and chronic effects resulting from exposure over a long period as in lung diseases such as asbestosis and silicosis. Contact dermatitis may result from the contact between the skin and some chemicals. Acids and alkalis are corrosive and can damage both skin and eyes.
Entry into the body
A chemical can cause injury in various ways depending upon whether it is solid or liquid, or in the form of airborne dust, vapour, fumes or gas. The routes into your body are by:
– inhalation or breathing in. This is the most important route of entry. Some toxic gases and vapours cause irritation in the nose and throat and so give warning of their presence; others do not and penetrate to the lungs or bloodstream. It is the smallest dust particles, those not visible to the naked eye, which reach furthest into the lungs. Inhaled dust accumulates in the lungs, producing changes and causing an incurable disease called “pneumoconiosis”. Breathlessness and inability to work are the eventual consequence. Some dust such as quartz and asbestos destroy the lung tissue and may lead to the development of tuberculosis or cancer;
– ingestion or swallowing. This is possible when you handle chemicals such as lead-based paints and then eat or smoke without first washing your hands, when toxic vapours contaminate cups, plates or eating utensils, or when you eat meals at the work site;
– absorption through the skin. Some solvents can be absorbed through the skin into the blood stream and may travel to internal organs such as the brain and liver. Contact dermatitis or eczema frequently results from the contact between the skin and some chemicals. Acids and alkalis are corrosive and can damage the skin and the eyes on contact. Unless large amounts of water are used at once to rinse the substance off, serious burns will be caused.
Discussion
• What construction processes cause the most dust?
• What precautions are taken?
• In what construction processes are fumes and vapours most likely to be encountered?
• What precautions have been taken on the site against the risk of inhalation of fumes and vapours?
Preventive measures
Accidents and ill health from the use of chemicals can be prevented if you know what chemicals you are using and the risks they pose, and follow the established safe practice in handling them. Generally, there is an order of priority in the measures for dealing with hazardous chemical substances:
• Substitute the chemical with a harmless or less hazardous one.
• Enclose the process using the chemical, or provide other engineering controls such as exhaust ventilation; this is often difficult in construction processes.
• Use personal protective equipment (PPE).
If the use of hazardous chemicals cannot be avoided, here are some basic safety measures you can adopt to protect yourself from danger:
– Keep containers of chemicals in a separate and secure store.
– Because two containers look the same, do not assume that they contain the same material.
– Make sure there is a label on the container (figure 48) – if there is no label, then do not use the contents.
– Read the label and make sure you understand what it says, then follow the instructions.
– If the information is not sufficient to tell you how to handle the chemical safely, ask your supervisor for the chemical safety data sheet (figure 49) and do not use the chemical until you have seen it; if you do not understand it, ask questions until you do.
– Check that you are wearing the correct PPE before you handle chemicals (the chemical safety data sheet should say whether you need gloves, eye protection, protective clothing, rubber boots or respirators) and that the equipment is in good order.
– When opening containers, hold a rag over the cap or lid as some volatile liquids tend to spurt up when this is released; transfer the contents of containers in the open air.
– Avoid breathing in any fumes from chemicals. Provide good ventilation, or work in the open air. Leave the work area immediately if you feel dizzy or unwell.
Point to remember:
• Some chemical hazards are easy to see or smell. However, there are also chemicals that you cannot see or smell, and which therefore present an extreme danger.
– If you are using large quantities of solvents, wear impermeable clothing. Remove any clothing wetted by solvents and leave it to dry in a well-ventilated place.
– Use the smallest quantity of chemicals that is necessary for the particular job.
– Eye protection should be worn when chemicals are being moved or transferred on site.
– When mixing or pouring chemicals using temporary containers, make sure they are suitable and correctly labelled. Never use food or drink containers.
– Wash before you eat and do not eat or smoke at your workstation.
– If the skin is splashed with a chemical, it should be rinsed immediately with plenty of clean running water. Eyes should be flushed out thoroughly with water and should receive immediate medical attention.
– If you are burned by a chemical or feel unwell after using a chemical, seek medical attention without delay.
– If there is a spillage of chemicals on the ground or floor, report the matter at once so that the right action can be taken, such as soaking it up in dry sand.
Point to remember:
• Never use solvents to remove paint or grease from your skin.
Highly flammable chemicals
Many chemical substances used in construction are highly flammable as well as toxic. The following precautions should be followed when handling or using them:
– Study the label and the instructions on the chemical safety data sheet about safe handling and first-aid measures.
– Remember that all flammable liquids give off vapours which travel unseen into the air and are easily ignited. Never smoke if there are flammable chemicals in the area. Find out what action to take in the case of fire.
– Keep containers in the store until required for use, and return them there when you have finished with them. Store drums upright.
– Treat empty drums with as much care as full ones – they will still contain flammable vapour.
– Always transfer the contents of large containers to small containers in the open air.
– Use funnels and spouts to prevent spillage. Soak up any spillage with dry sand and remove the contaminated sand to a safe place in the open air.
– If you cannot avoid using highly flammable liquids in an enclosed area, make sure there is an adequate supply of fresh air. This can usually be achieved by opening windows and doors to the full. If it is necessary to use a fan, check that the fan is electrically safe to use in a flammable atmosphere.
Discussion
• How would you recognize whether toxic or dangerous chemicals are being used on your construction site?
• Have you or anyone you know shown symptoms or suffered from using chemicals? If so, what were they?
• What steps do you think could have been taken, and were not taken, to prevent these ill-effects?
• What flammable chemicals have you used on construction sites?
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