2. How can workplace chemicals enter our body?No chemical substance can cause adverse effects without first entering the body or coming to contact with it. There are four main ways, that is routes of exposure, for chemical substances to enter the human body:
|
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. Picture 2
|
3. How chemicals affect us?The harmful effects of chemical substances depend on the toxicity and the exposure to that chemical. Toxicity is a property of the chemical substance, while the exposure depends on the way the chemical is used. The level of exposure depends on the concentration of the hazardous chemical and on the period of contact time. Many substances do not give any warning by odour, even though they may be present at dangerous concentrations in the workplace air.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. Picture 4
|
5. How to minimize the risks caused by chemicals?Improving safe use of chemicals can be achieved at different levels.5.1 In the enterpriseA Safety Committee should be formed with the task of working regularly with safety issues. It could start to work with following:Organizational measures
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.
5.2 At places of workA `Code of Practice' has been developed by the International Labour Organisation, and some countries have applied these principles for organizing hazard control. At the shop-floor level,a Safety Committee could:
5.3 StoragePlanning and maintaining storage areas is very relevant for users of chemicals in order to avoid material losses, accidents and disasters. Special attention should be paid to incompatible substances, suitable location of products within the storage area and proper arrangements and climatic conditions. For example, cylinders should be fixed with chains to upright position and the acids in the area or cupboard meant only for them. The fumes or splashes should never reach the area where cylinders are kept.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. 5.4 WasteChemicals react in the same characteristic ways whether they are wastes or are used in a production process. The hazards are also the same. Where chemicals are used, the enterprise should plan labelling, collecting and handling of wastes. Some countries have introduced legislation and provide detailed advises on how to treat dangerous chemical waste. To gain maximum benefit for all, a response is essential, from the shop-floor, where the chemicals are actually used, up to the management, which should plan the whole, safe `lifecycle' for every substance. Cooperation with and within authorities is needed to fulfill these tasks.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
ILO Recommendation 177, concerning safety in the use of chemicals at work |
BIBLIOGRAPHYARBETARSKYDDSNÄMNDEN, Kemiska hälsorisker, Gummessons Tryckeri, Falköping, Sweden, 1990BAKAR 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 HALTON D.M., How Workplace Chemicals Enter the Body, CCOHS, Canadian Centre for Occupational Health and Safety, Hamilton, Ontario, 1985 HSE, Health and Safety Executive, Essentials of Health and Safety at work, HMSO, London, 1990 ILO, International Labour Organisation, Code of Practice: Safety in the Use of Chemicals at Work, Geneva 1993 ILO, International Labour Organisation, Safety and Health in the use of Agrochemicals: A Guide, Geneva, 1991 IPCS, International Programme on Chemical Safety, How to use the IPCS Health and Safety Guides JOINT INDUSTRIAL SAFETY COUNCIL, Safety-Health and Working Conditions, TIBA Tryck AB, Stockholm, 1987 91/659/EEC Commission Directive of 3 December 1991 adapting to technical progress Annex I to Council Directive 76/769/EEC on the approximation of the laws, regulations and administrative provisions of the Member States relating to restrictions on the marketing and use of certain dangerous substances and preparations (asbestos) 2455/92/EEC Council Regulation of 23 July 1992 concerning the export and import of certain dangerous chemicals Sykes R., Vähäpassi A. and Ens H., Guidelines on Inspection of Chemical Factories, Especially Major Accident Hazard Installations, Jakarta, 1990 TUC, Trade Union Congress, Hazards at Work, TUC Guide to health and safety, Macdermott and Chant Ltd., London, 1988 |