ILO is a specialized agency of the United Nations


1. Chemical risks to health

Chemicals have become a part of our life, sustaining many of our activities, preventing and controlling many diseases, increasing agricultural productivity.

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.

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: 
  • Inhalation (breathing in) 
  • Absorption (through the skin or eyes) 
  • Ingestion (eating, swallowing) 
  • Transfer across the placenta of a pregnant woman to the unborn baby 
Picture 1
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
Picture 3
Solid chemicals can be used in different forms: cakes, pellets, granules, powder wetted with oil, paste. Think about dust formation when choosing the form.

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
Picture 5
Picture 6 What all we get from raw oil! This is a description of the product coming from fractional distillation of raw oil.
Picture 7
Picture 8

4. Common chemical groups that cause health risks

4.1 Dusts, fumes and gases

Dust may be just a nuisance, and the danger depends on the type of material in the dust, and on the amount and the size of the particles.

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.

4.2 Solvents

Most solvents are liquid organic chemicals. They are used because of their ability to dissolve other substances, particularly fat and grease, which are insoluble in water. Many of them evaporate rapidly at ambient temperatures. They are often flammable and may ignite by heat from smoking, welding or static electricity. Vapours move with air currents and can ignite even by a distant heat source.

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.

4.3 Metals

Metals can enter the body in the form of dust and fumes (in grinding or welding) or even through the skin. One of these is tetraethyl lead, which is used as an anti-knocking agent in petrol. Mercury vapours are often inhaled, as this liquid metal evaporates readily at room temperatures.

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.

4.4 Acids and bases

Strong acids and bases are mostly used as water solutions. They are corrosive to human tissue. Working with acids or bases can give rise to mists which have the same corrosive properties as the solutions.

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.

4.5 Pesticides

Pesticides are intended to destroy or control pests of all kind. They are used in industry, for example, to impregnate wood, and in agriculture to control insects, weed, fungi, and rats. These are many different types of pesticide compounds and they are used also as mixtures.

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: 

Organophosphorous compounds 
These are often acutely poisonous to insects and to humans. They can damage the nervous system and even cause death. They are effective even at low concentrations. Dichlorvos, demeton, parathion and thioazin belong to this group. 
Organochlorine compounds 
These compounds have a lower acute poisoning effect than organophosphorous compounds. They decompose slowly and can therefore accumulate in the environment and in the body. Aldrin, dieldrin, heptachlor, and DDT belong to this group. 
Carbamates are insecticides and fungicides 
They are poisonous to humans causing same type of symptoms as organophosphates. Dithiocarb and carbaryl belong to this group. 

Picture 9
Picture 10
Picture 11
Picture 12

5. How to minimize the risks caused by chemicals?

Improving safe use of chemicals can be achieved at different levels.

5.1 In the enterprise

A Safety Committee should be formed with the task of working regularly with safety issues. It could start to work with following:

Organizational measures

  • assess chemical hazards and set priorities concerning the safety in the organisation; 
  • create emergency plans for the assessed hazards; 
  • organize occupational health care and regular surveys as necessary; 
  • organize contacts with authorities/laboratories to createa monitoring system for chemical hazards, and to reliably measure and/or estimate occupational exposures to chemicals when needed; 
  • start collecting case studies of accidents and sickness records in the enterprise to create a basis for priority measures in the control of hazards; 
  • identify chemicals in use; 
  • obtain information of their hazards; 
  • collect this data and make an inventory list of all chemicals used in the factory: create a Register for Workplace Chemicals; 
  • involve workers in safety organizations, such as the system of Safety Representatives, and Safety Committees; 
Technical measures to control the hazard

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. 

An effective control method for any hazardous chemical is substitution: a hazardous chemical is replaced with a less hazardous one. This is especially important when the chemicals in question can cause cancer, damage to the reproductive functions or create allergic reactions. Choosing a safer process or changing an old and hazardous process to a less dangerous one effectively reduces the risks. 
An example of safer choice is to have pellets or paste instead of powdered substances which readily produce high levels of dangerous dusts. Water-based paints and adhesives are available to replace harmful products containing solvents.

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. 

Engineering control 
Closed system 
If hazardous chemicals can not be replaced by less dangerous ones, exposure must be prevented by protecting the worker. Enclosing the hazardous process or chemical is an effective method. 
One example is to use sealed pipes to transfer solvents and other liquids instead of pouring them in the open air. Vapours and gases caused by spray painting or produced in pickling or hardening baths in the metal industry should be controlled, ventilated and not allowed to enter the workplace air. 
Local exhaust ventilation 
It is not always possible to enclose all dangerous operations. A properly designed local exhaust ventilation is the second choice in order to remove the contaminants at the source. A local exhaust ventilation system consists of a hood, ducts or pipes, a system to collect and separate the pollutants from the clean air, and an efficient fan to create enough suction force. 
The hazardous gases, fumes and dust can be collected from the vented air. They should not go untreated, straight out, to pollute the surroundings of the factory and the environment. Attention should be paid to the clean air inflow which replaces the exhaust. Inspection, proper maintenance, regular cleaning and changing of filters are essential to protect the worker against hazardous contaminants. 
General ventilation 
Where it is difficult or impossible to prevent hazardous chemicals, fumes, dusts, mists or particles from entering the workplace air at the source, a general dilution ventilation can be installed. This should be designed to meet the needs of the specific work process and workplace. At its best it should consist of an inflow of clean air and an outflow of exhaust forced by fans at right places. It can also be used with other preventive measures. 
When working with dangerous chemicals, a proper housekeeping is essential. Storage areas must be well organized and kept in order. The transport of chemicals within the industrial premises should be planned and the transport routes kept clear. Maintenance of premises and equipment should also be planned. These tasks should be dedicated to persons/work groups/departments. Workers using the equipment should know the person responsible for repairing faulty equipment. 
Monitoring the efficiency of housekeeping and inspections should be carried out regularly; this should involve the workers themselves, who are experts in their own work.

Picture 13
Picture 14

5.2 At places of work

A `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: 
  • do regular inspection using checklists made for the particular chemicals and chemical processes in use; 
  • mark and label all chemicals; 
  • keep at hand an inventory list of all chemicals handled in the place of work together with a collection of chemical safety data sheets for these chemicals; 
  • train workers to read and understand chemical safety information, including the health hazards and routes of exposure; train them to handle dangerous chemicals and processes with respect; 
  • plan, develop and choose the safe working procedures; 
  • reduce the number of people coming into contact with dangerous chemicals; 
  • reduce the length of time and/or frequency of exposure of workers to dangerous chemicals; 
  • train workers to know and understand the emergency procedures; 
  • equip and train workers to use personnel protective equipment properly after all that is possible has been done to eliminate hazards by means of other methods. 

5.3 Storage

Planning 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 Waste

Chemicals 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:

Picture 15
Picture 16

  • Who is in charge of the job? 
  • Do their responsibilities overlap with those of anyone else? 
  • Is there anything which is not somebody's responsibility? 
  • Have the safe ways of doing the job been studied/chosen/applied? 
  • Is there any relevant code of practice or guidance note to be applied in this job? 
  • Did the worker get necessary training to do this job? 
  • Is the work safe or is the protective equipment needed? 
  • Is the user of protective equipment/clothing been informed of proper use and limitation of protective equipment? 
  • Who has assessed whether the tool, machines, protective equipment have the right capacity for the work to be done? 
  • What are the consequences if thing go wrong? 
  • How will the person in charge deal with any problems? 
  • If things do go wrong, would your people know what to do? Emergency plan? How to call an ambulance, firemen? 
  • If the work cannot be finished today can it be left in a safe state? Are clear instructions available for the next shift? 
  • How is the communication in your work place? Do those in production know what maintenance is going to be done, are any closures in some part of the production? Do the maintenance people know the special demands of the jobs related to the one they are working on? 
  • Is there any organized checking that the jobs are done in the way intended, or for general good house keeping? 
ILO Convention 170, concerning safety in the use of chemicals at work

ILO Recommendation 177, concerning safety in the use of chemicals at work


ARBETARSKYDDSNÄMNDEN, 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

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 

Table of contents | Next Chapter

Updated by AS. Approved by EC. Last update: 30.11.2004.