Safety in the Use of ChemicalsChapter 4Safety in the Use of Chemicals |
The responsibility to ensure that chemicals are used in a safe manner falls on the shoulders of everyone involved in their manufacture and supply: employers, supervisors, health and safety professionals, government inspectors and policy makers, and the users themselves -- the people of the planet.
Classification
The essential component of any chemical safety programme, whether at the national or at the enterprise level, is the classification of chemicals according to the hazards they may pose to the safety and health of users. Many countries have some kind of legislation which classifies chemicals according to their intended use as pesticides, pharmaceuticals, etc., and separate regulatory bodies and government agencies deal with these classes of chemicals. Many developing countries still lack a comprehensive system for classification of chemicals used in the workplace and at home. The basic criteria already discussed in previous chapters, such as the means of exposure, physical and chemical forms, short and long-term health effects, environmental impact, flammability and potential to cause explosions, can also be used as criteria for classification. On the basis of these classifications the chemicals may be assigned hazard classes, which may be identified with certain symbols and words easily understood by the ordinary user.
Identification
| Chemicals may come in many disguises. It is important that you know the contents of the package and the risks they may pose. Labels on containers and safety data instructions should contain information about the contents, health and safety hazards and control measures. |
Chemicals may come in many disguises. The same chemical used in different mixtures or even in pure form may be given different names by different manufacturers. Chemicals have chemical names (which indicate their chemical structure), but they may have a number of common names and trade names, which may confuse the user. An example is that of sulphuric acid, so commonly used in industry. Here are some of the examples of names sulphuric acid may be given in different circumstances.
Chemical name: Hydrogen sulphate
Common name: Sulphuric acid
Other names: Oil of vitriol, Battery acid
In fact, there are more than 50 common and trade names given to this chemical alone. Some trade names offer no clue about the identity of the ingredients. Sometimes fancy names like "tiger", "supergloss" or "karate" are given to potentially dangerous chemicals, sometimes only quaint names like "CH-RITE-54" are indicated on the container. Another example is that of bleaching powder:
Chemical name: Calcium hypochlorite
Other names: Calcium oxychlorite, Bleaching powder, Chlorinated lime
This variety of names can confound even those familiar with chemistry, not to speak of ordinary users. One of the first priorities of a successful chemical safety programme should be to identify the chemicals being used in the product. Containers of chemicals should show the list of chemicals inside. If not, suppliers and manufacturers should be required to provide such lists.
Some commercial preparations may have only one percent of a hazardous ingredient, which may not seem very great, but pose serious health risks. One way to identify a chemical is by its CAS number (Chemical Abstracts Service), given by the American Chemical Society. No matter how many different chemical or popular names a chemical may have, it can have only one CAS number. It is much easier to get information about a chemical if you have its CAS number.
Labelling
National legislation exists in most countries for provision of health and safety information for any potentially harmful chemical product sold for use in home or industry. In some countries, such legislation may cover only certain classes of chemicals, such as pesticides and pharmaceutical products. The label is the primary source of information about the identity, safe use, disposal and health and safety measures to be taken during the use of chemicals and in case of emergencies. It should contain the following information:
(i) Trade name of the chemical.
(ii) Identity of the chemical.
(iii) Name, address, telephone number of the supplier.
(iv) Hazard symbols.
(v) Nature of special risks associated with the use of the chemical.
(vi) Safety precautions.
(vii) Identification of the production batch
(viii) The statement that chemical safety data providing additional information is available from the employer
(ix) The classification assigned under the national laws
Unlabeled chemicals, like the sulphuric acid containers shown here, may cause grave risks to the safety and health of users
Users of chemicals must be informed about the interpretation of chemical hazard symbols and the specific precautions described in the labels. Several different symbol codes are in use in the world. These codes may vary from country to country. However, the most common chemical hazard symbols are those used by the European Community and the United States. Fig 4.1 provides a list of chemical hazard symbols used in the countries of the EC.
Fig 4.1 Hazard classification symbols used in the countries of the European Community
Material safety data sheets
While labels contain basic health and safety information about chemicals, more detailed but essential information is often found on the material safety data sheets which must accompany a hazardous product according to the laws of many countries. Various formats are used according to the manufacturers or the countries of origin of the products, but basically each safety data sheet must contain the following information:
(i) Name of the product and address of manufacturer.
(ii) Composition of the product.
(iii) Hazards the material may pose.
(iv) First-aid measures to be taken.
(v) Actions to be taken in case of accidental release.
(vi) Handling and storage information.
(vii) Exposure controls, including the types of personal protective equipment required.
(viii) Physical and chemical properties, including the reactivity and stability of the product.
(ix) Toxicological information and possible routes of entry into the body.
(x) Ecological and waste disposal information.
(xi) Transport information.
(xii) Regulatory information.
Some safety information sheets for commonly used chemicals in the developing countries are given at the end of this book.
Handling and use of chemicals
The ideal solution to the risks posed by chemicals is to avoid their use, but this may not be practicable in many cases. Sometimes hazardous products like gasoline are used as solvents simply because they are easily available. Such use of potentially hazardous chemicals and their handling should be avoided either by elimination of the hazardous product or the process or by substitution, using a less hazardous product process.
Other methods for the control of chemical hazards include isolation (contact between the user and the product is minimized by incorporating physical barriers) and ventilation, involving the removal or dilution of the hazardous chemicals in the air, so they are no longer a health risk.
Attention to basic rules can reduce chemical health and safety hazards. Empty and partially filled containers of chemicals result in risk of inhalation and fires and explosions. All containers should be tightly closed. Instructions on the labels and safety data sheets must be followed. When transferring chemicals from large to small containers, the small ones should also bear identification and safety labels. Always follow instructions on the label or material safety data sheet when mixing chemicals. Special attention should be paid to opening containers. Different containers have different opening devices, which could result in splashes on the body and spills.
Although personal protective equipment may be a bit uncomfortable, it must be used when needed. Personal protective equipment must be selected very carefully, and users must have training in proper use and care of it. A latex glove may be suitable for protecting hands from water soluble chemicals, but it may not provide protection against solvents. Similarly, a dust mask for aerosols does not work where gases and vapours are found.
Exposure to hazardous pharmaceutical dusts can be avoided by isolating the source of exposure and by ventilation, as shown here
Some situations to be avoided during handling of chemicals
Transport of chemicals
Major tragedies have happened during the transport of chemicals. On the job, efforts should be made to use pumps and mechanical means to transport chemicals to different areas. If large containers are to be carried, they should be transported by forklift trucks: rolling drums on the floors may result in spills. Chemicals which might react with each other should not be transported together.
Storage of chemicals
Chemical safety data sheets usually contain basic information regarding precautions during storage of particular chemicals. There are also general precautions which must be observed during storage of chemicals:
- Try to store only the minimum possible amounts. No unauthorized person should be allowed access to stored chemicals.
- Some chemicals are sensitive to moisture, others to sunlight, some to heat, still others to shock. This should be kept in mind while allocating area for storage.
- All containers being stored should be properly labeled.
- Firefighting and personal protective measures should be readily available in storage areas.
- Smoking, eating and drinking in chemical storage areas must be strictly prohibited.
- Do not store incompatible materials near each other; they may react and cause safety and health risks.
Chemical waste disposal
Wherever chemicals are used, wastes in the form of vapours or gases, liquids or solids are usually produced. Some of these wastes may be very hazardous to the ecology of the area as well as to the health of the people living in surrounding communities. Depending upon the type of waste, measures should be adopted to treat waste in such a way that ecological and public health risks are eliminated or minimized.
Most countries have some form of legislation which makes it difficult to release dangerous waste untreated into the environment. The exact technology of treatment and waste disposal can only be decided on the basis of the amount, chemical and physical nature and toxicity of the waste materials. Scrubbing, neutralization, electrostatic precipitation, chemical converters, burning (in the case of flammable materials) and filtration are used (alone or in combination with other methods) to treat or remove airborne pollutants.
For liquid wastes, treatment plants incorporating chemical neutralization, microbe degradation, sedimentation, filtration, etc. are customarily employed. For spills or leakages of hazardous liquids, absorbing material like sand, clay, wood dust, chemical powders, etc. are used to absorb the spill and then disposed of as solid waste or incinerated.
For particularly hazardous material, like hospital waste and many organic chemicals generated in large quantities, incinerators should be made available in different areas. Care must be observed in selecting the area for the disposal of solid waste, as it may seep intoto ground water or streams. Hazardous solid waste and waste with long life must be given special attention.
An example of filtration of air to remove suspended aerosols before release into the atmosphere.
Exercise
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