Potential Hazards of Chemicals

Research & Excerpt by Mr. R. R. Nair, Technical Advisor

1. INTRODUCTION
It is a fact that most of the chemicals available in the market are dangerous in one way or other and therefore it needs more attention to understand their potential hazards and control measures. A systematic approach to safety requires an efficient flow of information from the suppliers to the users of chemicals on the potential hazards of these chemicals and the safety precautions to be taken to minimize the hazards. Lack of awareness on these substances has caused many major accidents and some of them even have resulted in catastrophes like Bhopal, Mexico, Seveso, Chernobyl, etc. Therefore more attention is to be paid to create awareness amongst the users about the potential hazards of these substances. The number of chemicals used in industry is very large and grows each year. In the field of chemical safety, the first and foremost aspect is to classify and identify the chemicals according to their intrinsic hazards in a systematic way. Basic information regarding a chemical is a prerequisite for a systematic approach to chemical safety. Hence the identification of chemicals and knowing the nature of chemicals and their potential hazards become important.

2. IDENTIFICATION :
As the number of chemicals available in the market is very large and some chemicals are known in different names (synonyms) and trade names, it is difficult to identify the correct chemical without a proper identification number. All chemicals developed and marketed carry an identification number. The CAS number and UN number are the most internationally acclaimed numbering system for a chemical identity

2.1 CAS Number :
The CAS Registry Number is a number assigned to a material by the Chemical Abstracts Service (CAS), U.S.A., to provide a single unique identifier. For example, CAS No.1301 – 73 – 2 identifies the chemical, sodium hydroxide or caustic soda. The CAS Registry Number has no significance in terms of the chemical nature or hazards of the material.

2.2 UN Number :
United Nations Recommendations on the Transport of Dangerous Goods (UNRTDG) have allotted a specific 4-digit number (UN number) for the specific hazardous chemical or class of materials. For example, UN number for ammonia is 1005, and for corrosive liquid the number is 1760.

3. CLASSIFICATION SCHEMES :
The major basis for classification of chemicals is the assessment of exposure levels and environmental impact (water, air and soil). The most widespread criteria used in chemical classification are values of median lethal dose (LD50) and median lethal concentration (LC50). LD stands for lethal dose. LD is the amount of a material, given all at once, which causes the death of 50 percent (one half) of a group of test animals. LC stands for lethal concentration. LC50 is the concentration of a chemical in air which causes the death of 50 percent (one half) of a group of test animals in a given time (4 hours). These values are evaluated in laboratory animals via three main pathways – oral, dermal and inhalation – with a one-time exposure. The differences in the definitions of comparable hazard levels exist. While the European Community (EC) system utilizes a three-level acute toxicity scale (“very toxic”, “toxic” and “harmful”), the US Occupational Safety and Health Administration (OSHA) Hazard Communication Standard applies two acute toxicity levels namely highly toxic and toxic. Similarly, Manufacture, Storage and Import of Hazardous Chemicals Rules framed under the Environment (Protection) Act of India, applies only two toxicity levels, viz., extremely toxic and highly toxic.

3.1 Transport-oriented Classification :
Transport classifications, which are broadly applied, serve as a basis for regulations governing labeling, packaging and transport of dangerous cargoes. National classifications as a rule comply with UN, IMO and other classifications within international agreements on transportation of dangerous goods by air, rail, road and inland navigation, harmonized with the UN system. The UN Recommendations on Transport of Dangerous Goods (UNRTDG) create a widely accepted global system, which provides a framework for intermodal, international and regional transport regulations. These recommendations are increasingly being adopted as the basis of national regulations for domestic transport. The scope has been restricted to the transport of hazardous substances in packaged form. The recommendations do not apply to exposed hazardous chemicals or to transport in bulk. The UNRTDG focuses primarily on hazard communication based on labels, which include a combination of graphic symbols, colours, warning words and classification codes. They also provide key data for emergency response teams. The International Maritime Organization (IMO) has developed the International Maritime Dangerous Goods (IMDG) Code. The IMDG Code has been developed and kept up to date in close cooperation with the UN Committee of Experts on Transport of Dangerous Goods (UNCETDG) and has been implemented by IMO members representing about 85% of the world’s merchant tonnage.

3.2 Indicative Criteria :
The directive of the European Economic Council (EEC), which is at present known as European Union, has laid down various provisions relating to the classification of hazardous chemicals. On the other hand, a separate system of classification of the hazardous chemicals has been developed by the American National Standard Institute (ANSI) Apart from the above, the National Fire Protection Association (NFPA) in U.S.A has developed a standard system for the identification of the fire hazards of materials. The Standard applies to facilities for the manufacturing, storage or use of hazardous materials. It is concerned with the health, fire, reactivity and other related hazards created by short-term exposure that might be encountered under fire or related emergency conditions. It does not apply to transportation or to use by the general public. This standard provides a simple system of readily recognizable and easily understood markings, which will give at a glance a general idea of the inherent hazards of any material and the order of severity of these hazards as they relate to fire prevention, exposure and control. Its objectives are to provide an appropriate signal or alert and on-the-spot information to safeguard the lives of both public and private fire fighting personnel during fire emergencies.

3.3 Statutory Classifications in India :
In the Manufacture, Storage and Import of Hazardous Chemicals Rules, 1989, framed under the Environment (Protection) Act, classifications of chemicals as “toxic”, “flammable” and “explosives” have been made with indicative criteria. The indicative criteria for “toxic” chemicals as indicated are akin to those specified by the ANSI. As regards the flammable chemicals, the indicative criteria are similar to those laid down in the Indian Petroleum Rules. In the Central Motor Vehicles Rules, 1989, indicative criteria for both “toxic” and “flammable” chemicals have been laid down. Apart from the above, classification of the insecticides on the basis of their toxicity has been made in the Insecticides Rules, 1971.

4. LABELLING OF CHEMICALS :
Labels on containers of hazardous chemicals provide the first alert that a chemical is hazardous, and should provide basic information about safe handling procedures, protective measures, emergency first aid and the chemical’s hazards. The label should also include the identity of the hazardous chemical(s) and the name and address of the chemical manufacturer. Labeling consists of phrases as well as graphic and colour symbols applied directly on the product, package, label or tag. Several international organizations have established labeling content requirements for handling chemicals at the workplace and in transport. The Chemicals Convention, (No.170), and Recommendation, (No.177), of the International Labour Conference (ILC) establish requirements for the labeling of chemicals to ensure the communication of basic hazard information.

4.1 UN Danger Labels :
The UNRTDG establish five main pictograms viz., bomb, flame, skull and cross – bones, trefoil and liquid pouring out of two test tubes on a hand and a piece of metal. These symbols are supplemented by other representations such as flame above a circle, a glass bottle, three crescent signs superimposed on a circle and St. Andrews cross posed on wheat ear. The pictograms of UN danger labels are shown in Figure 1. The labels are all in the form of a square set at an angle of 45 degree (diamond shaped) with minimum dimension of 10 x 10 centimeters.

4.2 Indian Statutes :
The Section 6 of the Petroleum Act 1934 stipulates that a warning shall be displayed on all receptacles containing petroleum Class A, or near the receptacles. The warning, which should be in conspicuous characters, shall reveal the dangerous nature of the petroleum. Pipelines for transporting petroleum and wholly underground tanks are exempted.
The Rule 17(4) of the Manufacture, Storage and Import of Hazardous Chemical Rules, 1989, prescribes that every container of the ‘hazardous chemical’ shall be clearly labeled and marked to indicate the contents, and the flammable or explosive and toxic characteristics of the same.

The Rule 129 of the Central Motor Vehicles Rules, 1989, covers transportation of dangerous or hazardous goods. Every goods carriage used for such transportation as well as every package therein, containing such goods, shall display a distinct mark of the appropriate class label. Different types of class labels are indicated in the table annexed to the rule. Vide Rule 7(2) of the Hazardous Waste (Management and Handling) Rules, 1989, transportation of ‘hazardous wastes’ also is made to be governed by the above provision.

The Rule 73 – M (2) of the Maharashtra Factories Rules, 1963, stipulates that ‘every container of a hazardous substances shall be clearly labeled or marked to indicate the contents, the identity of the manufacturer or the importer, the potential hazards and the personnel protective equipment required to be used while at work with the substance.
The Rule 19 of the Central Insecticides Rules, 1971, stipulates the manner of labeling on the containers of insecticides. The information, which is to be printed or written with indelible ink on the label of the innermost container and outermost package, shall contain details of the antidote and other details. The square on the label shall contain prescribed symbols and warning statements.

5. STORAGE OF CHEMICALS
In many countries there is no control authority concerned with the supervision of the safety precautions for the storage of all dangerous substances, but a number of separate authorities exist. Each of these authorities, deal with a limited range of dangerous substances under various legislative powers. It is usually necessary to obtain a licence or permit from one of these authorities for the storage of certain type of dangerous substances such as petroleum, explosives, cellulose and cellulose solutions. The licensure procedures require that storage facilities comply with specified safety standards. The International Maritime Dangerous Goods (IMDG) code makes recommendations regarding segregation ranging from the most stringent requirements to a requirement to store the incompatible materials at least 3 meters apart. Some of the common chemicals and their incompatibilities are given in Table 1.

6. NATURE OF SUBSTSNCES
Knowledge of hazardous parameters of chemicals is one of the basic conditions for safe working with chemicals. According to the nature of hazards, the chemicals may be broadly classified as follows:

  • Combustible substances
  • Explosives substances
  • Flammable (Inflammable) substances
  • Substances react with air and/or water, subject to spontaneous combustion
  • Chemically unstable substances
  • Oxidizing substances
  • Toxic substances
  • Radioactive substances
  • Corrosive substances

The nature and potential hazards of the above substances are dealt briefly in the following paragraphs;

6.1 Combustible Substances :
The combustible substances are substance, which are liable to continue to burn if ignited. Some substances (e.g. nitrocellulose, matches, etc) are more readily combustible than others. In some cases solids in powder form can be ignited fairly easily. It can also, if disposed as a dust cloud, burn with explosive violence. Examples of combustible substances are: (1) cold dust, (2) flour.

6.2 Explosive Substances :
These substances are used for many military and industrial purposes. Explosive substances are chemicals and mixtures which, when affected by strong mechanical force (hitting, shock, friction) or starting ignition, suddenly transform to gases of large volume through an extremely rapid oxidizing reaction. The volume of these gases is the multiple of the volume of the explosive material already exploded, and they will exert very high pressure on surroundings. During an explosion, high temperatures can arise (2,500 to 4,0000C) that promote the ignition of the combustible materials in the zone of explosion. Besides the explosive materials used for military and industrial purposes, the inductive blasting materials and pyrotechnical products are also treated as hazards. The mixtures of explosive materials often used are: (i) picric acid, (ii) nitroglycerine, (iii) hexogen, etc. The mixtures of materials capable of explosion are: (i) black powder, (ii) dynamite, (iii) ammonium nitrate, etc. In the course of acts of terrorism, plastic materials have become well-known, and are, in essence, mixtures of plasticizing materials such as Waxes, Vaseline, etc.

For explosive materials, the most effective method of protection against fire is the exclusion of ignition sources from the surroundings. Several explosive materials are sensitive to water or various organic materials with ability to oxidize. For these materials, the requirements for the conditions of storage and the rules for storing in the same place together with other materials should be carefully considered. The storage places should be situated far away from other buildings and structures so as to minimize damage in case of an explosion. Manufacturer’s of explosives, issue instructions as to the most suitable type of storage. The storerooms should be of solid construction and kept securely locked when not in use. No store should be near a building containing oil, grease, waste, combustible material or flammable material, open fire or flame. Magazines should preferably be located at least 60 meters away from any power plant, tunnel, dam, highway or building. Advantage should be of any protection offered by natural features such as hills, hollows, dense woods or forests. Artificial barriers of earth or stone walls are sometimes placed around such storage places. The storage place should not be damp and well ventilated. Natural lighting or portable electric lamps should be used. Floors should be of wood or other non-sparking material. The area surrounding the storage place should be kept free of a dry grass, rubbish or any other material likely to burn. Black powder and explosives should be stored in separate store-houses; No detonators, tools or other material should be kept in an explosive store. Non-ferrous tools should be used for opening cases of explosives.

6.3 Flammable Substances :
The flammable substance can be in gaseous, liquid, or solid form. Although all materials under specific temperature and pressure may become gases, the materials considered gaseous in practice are those that are in a gas state at normal temperature (200C) and normal atmospheric pressure (100kPa). Gases may be grouped into two main groups viz., (i) combustible gases and (ii) non-combustible gases. According to the definition accepted in practice, combustible gases are those that burn in air with normal oxygen concentration, provided that the conditions required for burning exist. Ignition only occurs above a certain temperature, with the necessary ignition temperature, and within a given range of concentration. Non-combustible gases are those that do not burn either in oxygen or in air with any concentration of air. A portion of these gases support combustion (e.g. oxygen), while the other portion inhibit burning. The non-combustible gases not supporting burning are called inert gases (e.g. Nitrogen, Noble gases, Carbon dioxide, etc). The gases stored and transported in containers or transporting vessels are typically in compressed, liquefied, or cooled – condensate (cryogenic) state. Basically, these are two hazardous situations in connection with gases i.e. when they are in containers and when they are released from their containers.

For compressed gases in storage containers, external heat might considerably increase the pressure within the container, and the extreme power pressure might lead to explosion. The storage containers are generally required to contain the application of over pressure relief devices. These are capable of mitigating a hazardous situation due to higher temperatures. If the storage vessels are insufficiently sealed or damaged, the gas will flow out to the free air space, mix with air and depending on its quantity and the way of its flowing, may cause the formation of a large, explosive air space.

The air around a leaking storage vessel can be unsuitable for breathing and may be dangerous for people nearby, partially due to the toxic effect of some gases and partly due to the diluted concentration of oxygen. Flammable gases and liquids can readily produce flammable vapour/air mixtures at ordinary and ambient temperatures. Vapours of such mixtures can be ignited by sparks from electrical equipment or static electricity produced during drum-filling operations as well as by the more-obvious naked flame. For a liquid, indication of the degree of flammability is provided by the flash point of the product; this is the lowest temperature at which a product will form a flammable vapour/air mixture. Examples of flammable gases and liquids are: (i) Gases (LPG, Camping gas) and (ii) Liquids (Hydrocarbon solvents, Alcohols, Ketones). Care must be exercised in the use of forklift trucks in areas where these substances are stored. Electrically powered forklift trucks for use in drum or container storerooms should be protected. Non-sparking, not necessarily flameproof, equipment would be suitable. Diesel engine equipment intended for continuous use should be protected in accordance with the “recommendations for the protection of diesel engines operating in hazardous areas”.

The storage area should be situated away from any source of heat or fire hazards. Highly flammable substances should be kept apart from powerful oxidizing agents or from materials which are susceptible to spontaneous combustion. When highly volatile liquids are stored, any electric light fillings or apparatus should be of certified flameproof construction. No open flames should be permitted to or near the storage place. Fire Extinguishers and earth, should be available for emergency situations. The walls, ceilings and floors of the storage room should consist of materials of fire resistance. The room should be fitted with self closing fire doors. The storage room installation should be electrically grounded and periodically inspected. The storage room should be equipped with automatic smoke or fire detection device.

6.4 Substances React with Air and/or Water :
The substances sensitive to water and air are extremely dangerous. These substances interact with water and air that are always present in the normal atmosphere, and start reactions accompanied by very high heat generation. If they are combustible materials, they will come to spontaneous ignition. However, the combustible components that initiate the burning may possibly explode and spread to the combustible materials in the surrounding area. Examples of substances react with air and/or water are: (i) Oxides, (ii) Hydroxides, (iii) Hydrides, (iv) Anhydrides, (v) Alkali metals and (vi) Phosphorous etc.

Table – 1
COMMON CHEMICALS AND THEIR INCOMPATIBLE CHEMICALS

Name of Chemical Name of Incompatible Chemicals
Acetic acid Chromic acid, nitric acid, hydroxyl compounds, ethylene glycol, perchloric acid, peroxides, permanganates
Acetylene Chlorine, bromine, copper, fluorine, silver, mercury
Acetone Concentrated nitric and sulfuric acid mixtures
Alkaline metals (powdered  aluminum, magnesium, calcium, lithium, sodium, potassium) Water, carbon tetrachloride or other chlorinated hydrocarbons, carbon dioxide, halogens
Ammonia (anhydrous) Mercury, chlorine, calcium hypochlorite, iodine, bromine, hydrofluoric acid (anhydrous)
Ammonium nitrate Acids, powdered metals, flammable liquids, chlorates, nitrates, sulfur, finely divided organic or combustible materials
Aniline Nitric acid, hydrogen peroxide
Arsenical materials Any reducing agent
Azides Acids
Bromine See Chlorine
Calcium oxide Water
Carbon (activated) Calcium hypochlorite, all oxidizing agents
Carbon tetrachloride Sodium
Chlorates Ammonium salts, acids, powdered metals, sulfur, finely divided organic or combustible materials
Chromic acid and chromium trioxide Acetic acid, naphthalene, camphor, glycerol, alcohol, flammable liquids in general
Chlorine Ammonia, acetylene, butadiene, butane, methane, propane (or other petroleum gases), hydrogen, sodium carbide, benzene, finely divided metals, turpentine
Chlorine dioxide Ammonia, methane, phosphine, hydrogen sulfide
Copper Acetylene, hydrogen peroxide
Cumene hydroperoxide Acids (organic or inorganic)
Cyanides Acids
Ethylene Oxide Acids , bases, copper, magnesium, perchlorate
Hydrocyanic acid Nitric acid, alkali
Flammable liquids Ammonium nitrate, chromic acid, hydrogen peroxide, nitric acid, sodium peroxide, halogens
Hydrocarbons (butane, propane,
benzene, petrol, turpentine, etc.) Fluorine, chlorine, bromine, chromic acid, sodium peroxide, nitric acid
Hydrogen sulfide Fuming nitric acid, oxidizing gases
Hypochlorites Acids, activated carbon
Nitroparaffins Inorganic bases, amines
Nitroparaffins Inorganic bases, amines
Mercury Acetylene, fulminic acid, ammonia
Nitrates Sulfuric acid
Iodine Acetylene, ammonia (aqueous or anhydrous), hydrogen
Oxygen Oils, grease, hydrogen, flammable liquids, solids, or gases
Phosphorus (white) Air, oxygen, alkalis, reducing agents
Oxalic acid Silver, mercury
Hydrofluoric acid (anhydrous) Ammonia (aqueous or anhydrous)
Hydrogen peroxide Copper, chromium, iron, most metals or their salts, alcohols, acetone, organic materials, aniline, nitromethane, combustible materials
Nitric acid (concentrated) Acetic acid, aniline, chromic acid, hydrocyanic acid, hydrogen sulfide, flammable liquids, flammable gases, copper, brass, any heavy metals
Perchloric acid Acetic anhydride, bismuth and its alloys, alcohol, paper, wood, grease, oils
Peroxide, organic Acids (organic or mineral), avoid friction, store cold
Potassium Carbon tetrachloride, carbon dioxide, water
Potassium chlorate Sulfuric and other acids
Potassium perchlorate Sulfuric and other acids
Potassium permanganate Glycerol, ethylene glycol, benzaldehyde, sulfuric acid
Silver Acetylene, oxalic acid, tartartic acid, ammonium compounds, fulminic acid
Sodium Carbon tetrachloride, carbon dioxide, water
Sodium nitrate Ammonium nitrate and other ammonium salts
Sodium peroxide Ethyl or methyl alcohol, glacial acetic acid, acetic anhydrite, benzaldehyde, carbon disulfide, glycerin, ethylene glycol, ethyl acetate, methyl acetate, furfural
Sulfuric acid Potassium chlorate, potassium perchlorate, potassium permanganate (similar compounds of light metals, such as sodium, lithium)

6.5 Chemically Unstable Substances :
The chemically unstable substances include the chemicals, which polymerize or decompose in violent exothermic reactions spontaneously or very easily. Examples of chemically unstable substances are: (i) Acetaldehyde, (ii) Ethylene oxide, (iii) Organic peroxides, (iv)Hydrogen cyanide and (v) Vinyl chloride.

6.6 Oxidizing Substances :
Oxidizing substance are substances, which supply oxygen and do therefore readily assist and maintain combustion. Even if they themselves are non-combustible, largely contribute to the ignition of combustible materials and to their intensive, occasionally explosive burning. Examples of oxidizing substances are : (i) Oxygen, (ii) Chlorine and (iii) Peroxide Compounds. Also some oxidizing agents, for example concentrated nitric acid, may create fire if they come into contact with organic substances such as timber or packing materials. Storage rules must therefore be strictly observed and in particular sodium chlorate should never be stored on wooden pallets. Powerful oxidizing substances should be stored near liquids that have a low flash point or even slightly flammable materials. The storage area should be cool, well ventilated and of fire resisting construction.

6.7 Toxic Substances :
Toxic Substances are substance, which may cause harmful effects by absorption into the body by (i) inhalation (breathing) the vapour or mist, (ii) absorption through skin and (iii) ingestion (entry into mouth and swallowing). Some of the toxic substances are also potential fire hazard and may act in two ways. First, the high toxicity of certain chemicals themselves may be hazardous in a fire. Second, their presence within the free zone may effectively restrict fire-fighting operations. It is important that adequate personal protective clothing is available for use when clearing up spillages of toxic products. This will include suitable gloves, boots, eye shields and, where appropriate, face masks or even breathing apparatus. Ideally ventilation of the building should be such to minimize accumulation of toxic vapours should au unforeseen incident (such as a drum leaking) occur. Spillages should be dealt with in such as way as to avoid contamination of surface water drains. Toxic chemicals should be stored in cool, well-ventilated areas, out of contact with heat, acids, moisture and oxidizing substances. The material should not be exposed to direct rays of sun, and away form all sources of Ignition. Store rooms should be equipped with exhaust hoods or equivalent local ventilation devices. Open containers should be closed with tape or other sealant before being returned to the storeroom. The substances, which can react with other chemicals, should be kept in separate stores.

6.8 Radioactive Substances :
The dangerous characteristic of radioactive substances and components is increased by the fact that the radiation emanated by them may be harmful in several ways, besides that such materials may be fire hazards themselves. If in a fire the structural containment of the radioactive objects involved becomes damaged, γ-radiating materials might be released. They can have a very strong enhancing effect, and are capable of the fatal destruction of living organisms. Nuclear accidents can be accompanied by fires, the decomposition products of, which bind radioactive (α-and β-radiating) contaminants by adsorption. These may cause permanent injuries to the persons taking part in rescue operations if they penetrate into their bodies. Such materials are extremely dangerous because the persons affected do not perceive any radiation by their sensing organs, and their general state of health does not seem to be may be worse. It is obvious that if radioactive materials burn, the radioactivity of the site, the decomposition products and the water used for fire fighting should be kept under constant observation by means of radioactive signaling devices. The knowledge of these factors has to be taken into account for the strategy of intervention and all additional operations. The buildings for handling storing radioactive materials as well as for their technological use needs to be built of non-combustible materials of high fire resistance. At the same time, high-quality, automatic equipment for detecting, signaling and extinguishing a fire should be provided.

6.9 Corrosive Substances :
Corrosive substances are products that will attack and/or eat away skin, metals etc. Corrosiveness of these substances varies between substances. Such products are sometimes flammable and they may be toxic as well as corrosive. The majority of the corrosive materials are strong oxidizing agents, but at the same time they have very strong destructive effects on leaving tissues. It is important, when dealing with spillages of these substances, that adequate protective clothing, as advised by the supplier, is worn so as to avoid any contact with the body.

7 CONCLUSION :
Chemicals play an important role in many workplace applications. They can be nasty things to deal with. They come in different forms: solids, liquids and gases. Many chemicals can affect your health. Some chemicals such as formalin, can kill you within seconds. Other chemicals burn your skin, destroy your lungs, affect your digestive system, poison you, give you cancer, and even make you sterile. Some other chemicals are volatile and can burn or explode if not handled correctly. Lack of safety measures along with a limited knowledge of potential hazards of chemicals often leads to several dangerous incidents and fatalities in the industry. Attempts should therefore be made to minimize the frequency of such accidents including their possible impacts.

REFERENCES

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