1. INTRODUCTION TO SAFETY IN THE USE OF CHEMICALS
However one can not ignore that many of these chemicals may, especially if not properly used, endanger our health and poison our environment.
It has been estimated that approximately one thousand new chemicals come onto the market every year, and about 100 000 chemical substances are used on a global scale. These chemicals are usually found as mixtures in commercial products. One to two million such products or trade names exist in most industrialized countries.
More substances and rising production mean more storage, transport, handling, use and disposal of chemicals. The whole lifecycle of a chemical should be considered when assessing its dangers and benefits.
Most chemical accidents have a limited effect. Occasionally there is a disaster like the one in Bhopal, India, in 1984, with thousands of deaths and many people permanently disabled.
It is not just the worker handling chemicals who is at risk. We may be exposed in our homes through misuse or by accidents, and be contaminated by consumer products including food.
The environment may be affected, chemicals may pollute the air we breathe, the water we drink, and the food we eat. They may have entered into forests and lakes, destroying wildlife and changing the ecosystems.
Chemicals are not all of equal concern. The assessment of health risks of chemical substances is a continuous process where information of the chemical hazards is made available through a variety of sources.
Remember: chemicals have power, and that is why they have become an important part of our life. Respect that power and handle them with care.
|Most chemicals used at the place of work may be dispersed into the
air to form dust, mist, fumes, gas or vapour and can then be inhaled. In
this way also workers who are not actually handling them but stay within
the reach can be exposed to a mixture of chemicals from various sources.
Handling chemical substances without proper protection exposes the worker to the risk of absorbing harmful amounts of chemical through the skin. This usually happens when handling the chemical in liquid form. Dust may also be absorbed through the skin if it is wetted by, for instance, sweat. The capacity of different chemical substances to penetrate the skin varies considerably. Some substances pass through it without creating any feeling. Skin absorption is, after inhalation, the second most common route through which occupational exposure may take place.
The protective external layer of skin may be softened (by toluene, dilute washing soda solution, etc) thus permitting other chemicals to enter readily to the bloodstream (such as aniline, phenol, benzene, etc).
Eyes may also absorb chemical substances, either from splashes or from vapours.
Dangerous chemicals can enter the body through ingestion as gases, dusts, vapours, fumes, liquids or solids. Inhaled dust may be swallowed, and food or cigarettes may be contaminated by dirty hands. Eating, drinking and smoking should be prohibited at a place of work where dangerous chemicals are used.
Whatever the route of entry, chemicals can reach the blood stream and be distributed all over the body. In this way damage can be caused at the site of entry as well as to organs distant from the exposed area.
Acute effects - Chronic effects
The effects may be acute: after a short exposure an immediate effect may be experienced. Chronic effects usually require repeated exposure and involve a delay between the first exposure and appearance of adverse health effects.
A substance may have acute and chronic effects. Both acute and chronic conditions can result in permanent injury.
Injury from exposure to a chemical substance can be temporary, i.e. reversible. It will disappear when exposure to that chemical stops.
Exposure to solvents may cause contact dermatitis, headache or nausea. These effects could be both acute and temporary. Solvents can also cause chronic effects and result in an irreversible, permanent injury to the nervous system.
Local effects - Systemic effects
Hazardous substances may cause local effects. Acute local effects may include corrosive injuries from acids and bases or lung injuries from inhaled gases such as ozone, phosgene and nitrogen oxides.
Many other gases cause adverse effects only after they have been inhaled repeatedly over a long time period. Low concentrations of a gas may also be effective in this way. A persistent irritation of the respiratory system can arise from exposure to gases such as sulphur oxides, hydrogen fluoride and hydrogen chloride.
Once the hazardous substance has entered the blood circulation, it may be distributed to all parts of the body. It will reach the liver, which is the most important detoxication organ of the body. The liver attempts to convert the toxic agents to a less toxic ones or to the ones useful to the body. This process is called metabolism. Some substances such as alcohol and carbon tetrachloride can damage the liver. The body excretes unwanted chemicals. The kidneys filter them from blood circulation, which is the main way that the body excretes poisons, but in doing this, they can be damaged by toxic substances such as carbon tetrachloride, ethylene glycol and carbon disulphide. Cadmium causes permanent damages to kidneys.
Other means of excretion are via faeces, sweat and through lung exhalation.
The nervous system is sensitive to chemicals. The adverse effects may be on the central nervous system or on the nerves that transport impulses to other parts of the body. Organic solvents are commonly used at work and are known to be able to affect the nervous system. Many other substances may behave in the same way such as carbon disulphide, mercury, lead, manganese and arsenic.
Our body has a considerable capacity to excrete, to render dangerous substances harmless, and to protect us. However, our defense system can be overloaded by repeated heavy exposure so that it no longer fulfills its function. The body stores the harmful substance which may consequently result in health problems.
Lead is an example of a substance for which removal from the body takes a long time. Cadmium is an example of a substance that is not processed by the body at all, and once it has entered it will stay there.
The smaller the particle is the deeper it will penetrate into the lungs with the inhaled air, thereby passing the defensive systems of the lungs. This type of dust is invisible to the eye and identified using microscope technique. Such dust can accumulate in the lungs over a long period of time and cause a lung disease called pneumoconiosis, which is a common incapacitating occupational disease. Dusts containing crystalline silica or asbestos are particularly dangerous.
Sand and many types of stone contain crystalline silica, as do many ores, concrete, ceramics and diatomite. Processing of these materials creates dust with result of silica accumulating in the lungs. This may lead after years to a incurable lung disease, even though the exposure has been stopped years before.
Asbestos is a natural mineral fibre which is very resistant to fire and to many chemicals. Asbestos fibres are very strong and thin. Asbestos exists in various forms and names: chrysotile, crocidolite, amosite, anthophyllite, actinolite and tremolite asbestos. Chrysotile is used in isolating materials, protective carpets and clothes.
The dust penetrates the lungs destroying the lung tissue. This condition is called asbestosis. Asbestos can also cause lung cancer. The risk of cancer is many times higher if the asbestos exposure is combined with smoking. Many countries have restricted or banned the use of asbestos.
Exposure to metal fumes can cause damage to the body. `Metal fume fever' is a known health effect when metal fumes, often containing zinc, are inhaled. It usually appears on the day following that of the exposure.
Gases do not necessarily have a warning odour at a dangerous concentration. The odour may be apparent only at very high concentration in the air. Gases may have an irritating effect, or they may enter the blood circulation and cause internal damage.
Sulphur oxides, nitrogen oxides, chlorine and ammonia are toxic gases that are corrosive and irritating to the respiratory system. They are widely used in industry. Phosgene is formed when solvents containing chlorine, such as "TRI" (1,1,2- trichloroethylene), come into contact with hot surfaces or flames. Phosgene can be deadly poisonous even before the odour is detected.
Carbon monoxide is a toxic, odourless, colourless gas which is formed by the incomplete burning of materials of organic origin. It may enter the blood circulation. Some gases can pass through the skin, for example, hydrogen cyanide.
Inhalation is the most common way for solvents to enter the body, but some of them penetrate intact healthy skin. Once in the blood stream a solvent can be transported to different organs, such as the brain and liver.
Solvents have different effects on humans, depending on their evaporation rate and their solubility in water. The risks of health effects depend on the period of exposure and the concentration of the solvent in the inhaled air.
Many solvents have a narcotic effect; they may cause dizziness, headache, reduced comprehension or tiredness. They may also irritate the eyes and the respiratory tract. Frequent skin contact defats the protective layer of the skin causing irritation. Some solvents are very hazardous to the liver, kidneys, bone marrow or nervous system. Benzene, carbon tetrachloride and carbon disulphide belong to the category of solvents which should be substituted with less dangerous ones.
Lead is used in various industries: battery, glass and mining industries, cable manufacturing, foundries and in printing works. Steel constructions are protected with anti-corrosive paint containing lead, which may be released during welding operations, for example, on ships.
Mercury is present in many pesticides and pickling baths. In the environment, it may accumulate in fish. Mercury poisoning has serious effects on the nervous system.
Nickel is present with other metals in various alloys. Nickel and its compounds are known to be sensitizers. Once a person has had an allergic reaction to nickel, the reaction reoccurs following the contact with very small amounts of nickel used in products such as leather, cement, or door handles. Some compounds of nickel can cause cancer.
Chromium compounds, particularly chromates and bichromates, are widely used in industry. Cement contains small amounts of chromium compounds. These compounds can cause allergy and even lung cancer. Unlike cobalt and nickel, pure metallic chromium does not cause allergy. Chromium compounds may cause birth defects if mothers are exposed to these compounds during pregnancy.
Arsenic compounds are used in pesticides, insecticides and in some colouring materials. Chronic arsenic poisoning can start with irritation to the respiratory system, inflammation of the eyes, or skin problems, followed by damage in nervous system. Arsenic and its compounds can cause cancer.
When acids and bases are mixed with each other the phenomena of neutralization occurs, usually with strong production of heat. The heat production has particularly serious effects when water is added to concentrated sulphuric acid: the heat will splash the highly corrosive liquid up, risking injury to the worker.
Some acids are explosive when in contact with organic material, such as sawdust.
Serious damage can result when treating metal pieces in a acid bath. The bath may contain more than one acid in a mixture and may release flammable hydrogen gas, as well as acid mist, when a piece of metal is placed in it.
Phosphoric acid is used to treat metals. When in contact with hot surfaces, phosphoric acid can give off poisonous gases. Ammonia, sodium and potassium hydroxides are commonly used bases. They are corrosive to human tissue in such a way that a certain period of time is required before the corrosive feeling is sensed. Bases penetrate the skin and cause deep sores. They are difficult to wash away. Dilute water solutions are irritating.
Sodium and potassium hydroxides are used, for example, in hot degreasing baths for cleaning metals.
Some countries apply restrictions in using certain compounds, and the use of some of them is completely banned because of their serious adverse effects. In Europe, the list of banned pesticides includes compounds such as inorganic mercury compounds, camphechlor, chlordane, dieldrin, DDT, HCH (lindane), heptachlor, hexachlorobenzene, and nitrofen.
Insecticides are divided into following broad groups:
Technical measures can be used to prevent chemical hazards at source, and to prevent the transfer of dangerous chemicals. By technical means it is possible to reduce the exposure of the worker.
All possible information should be made available when considering the change of a substance or the whole process so that the new choice does not create unexpected new dangers.
Hazardous substances can leak, cause a fire or give off dangerous fumes and vapours. When two substances come into contact with one another, they may react violently. The reaction products may be much more dangerous than the original chemicals.
Written instructions of storage practices should be provided, and chemical safety data sheets of dangerous substances kept in stock should be available in the storage area.
Many accidents have based on a good belief that everyone is aware of the situation. Discuss in the work place the ideas arising when asking the following questions:
|CHECKLIST TO SAFETY MANAGEMENT
BIBLIOGRAPHYARBETARSKYDDSNÄMNDEN, Kemiska hälsorisker, Gummessons Tryckeri, Falköping, Sweden, 1990
BAKAR CHE MAN A. and GOLD D., Safety and Health in the use of Chemicals at Work: A training manual, ILO, Geneva, 1993
FAO, Food and Agriculture Organization of the United Nations, International Code of Conduct on the Distribution and Use of Pesticides, Rome 1990
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HSE, Health and Safety Executive, Essentials of Health and Safety at work, HMSO, London, 1990
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ILO, International Labour Organisation, Safety and Health in the use of Agrochemicals: A Guide, Geneva, 1991
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2455/92/EEC Council Regulation of 23 July 1992 concerning the export and import of certain dangerous chemicals
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