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Classification and Labeling Systems for Chemicals

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Hazard classification and labelling systems are included in legislation covering the safe production, transport, use and disposal of chemicals. These classifications are designed to provide a systematic and comprehensible transfer of health information. Only a small number of significant classification and labelling systems exist at the national, regional and international levels. Classification criteria and their definitions used in these systems vary in the number and degree of hazard scales, specific terminology and test methods, and the methodology for classifying mixtures of chemicals. The establishment of an international structure for harmonizing classification and labelling systems for chemicals would have a beneficial impact on chemical trade, on the exchange of information related to chemicals, on the cost of risk assessment and management of chemicals, and ultimately on the protection of workers, the general public and the environment.

The major basis for classification of chemicals is the assessment of exposure levels and environmental impact (water, air and soil). About half of the international systems contain criteria related to a chemical’s production volume or the effects of pollutant emissions. The most widespread criteria used in chemical classification are values of median lethal dose (LD50) and median lethal concentration (LC50). These values are evaluated in laboratory animals via three main pathways—oral, dermal and inhalation—with a one-time exposure. Values of LD50 and LC50 are evaluated in the same animal species and with the same exposure routes. The Republic of Korea considers LD50 with intravenous and intracutaneous administration as well. In Switzerland and Yugoslavia chemical management legislation requires quantitative criteria for LD50 with oral administration and adds a provision which specifies the possibility of different hazard classifications based on the route of exposure.

In addition, 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 (“highly toxic” and “toxic”). Most classifications apply either three categories (United Nations (UN), World Bank, International Maritime Organization (IMO), EC and others) or four (the former Council for Mutual Economic Assistance (CMEA), the Russian Federation, China, Mexico and Yugoslavia).

International Systems

The following discussion of existing chemical classification and labelling systems focuses primarily on major systems with long application experience. Hazard assessments of pesticides are not covered in general chemical classifications, but are included in the Food and Agricultural Organization/World Health Organization (FAO/WHO) classification as well as in various national legislation (e.g., Bangladesh, Bulgaria, China, the Republic of Korea, Poland, the Russian Federation, Sri Lanka, Venezuela and Zimbabwe).

Transport-oriented classifications

Transport classifications, which are broadly applied, serve as a basis for regulations governing labelling, packaging and transport of dangerous cargoes. Among these classifications are the UN Recommendations on the Transport of Dangerous Goods (UNRTDG), the International Maritime Dangerous Goods Code developed within the IMO, the classification established by the Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP) for hazardous chemicals carried by ship, as well as national transport classifications. 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 United Nations Recommendations on the Transport of Dangerous Goods and related transport modal authorities

The 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 UNRTDG is rather general on issues such as notification, identification and hazard communication. 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. Originally the objective was to prevent dangerous goods from causing acute injury to workers or the general public, or damage to other goods or the means of transport employed (aircraft, vessel, railcar or road vehicle). The system has now been extended to include asbestos and substances hazardous to the environment.

The UNRTDG focus 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 UNRTDG are relevant for the protection of such transport workers as aircrew, mariners and the crews of trains and road vehicles. In many countries the Recommendations have been incorporated in legislation for the protection of dock workers. Parts of the system, such as the Recommendations on explosives, have been adapted to regional and national regulations for the workplace, generally including manufacturing and storage. Other UN organizations concerned with transport have adopted the UNRTDG. The transport classification systems of dangerous goods of Australia, Canada, India, Jordan, Kuwait, Malaysia and United Kingdom basically comply with the major principles of these Recommendations, for example.

The UN classification subdivides chemicals into nine classes of hazards:

    • 1st class—explosive substances
    • 2nd class—compressed, liquefied, dissolved under pressure or deeply condensed gases
    • 3rd class—easily inflammable liquids
    • 4th class—easily inflammable solid substances
    • 5th class—oxidizing substances, organic peroxides
    • 6th class—poisonous (toxic) and infectious substances
    • 7th class—radioactive substances
    • 8th class—corrosive agents
    • 9th class—other dangerous substances.


                    The packaging of goods for the purpose of transport, an area specified by the UNRTDG, is not covered as comprehensively by other systems. In support of the Recommendations, organizations such as IMO and International Civil Aviation Organization (ICAO) carry out very significant programmes aimed at training dock workers and airport personnel in the recognition of label information and packaging standards.

                    The International Maritime Organization

                    The IMO, with a mandate from the 1960 Conference on Safety of Life at Sea (SOLAS 1960), has developed the International Maritime Dangerous Goods (IMDG) Code. This code supplements the mandatory requirements of chapter VII (Carriage of Dangerous Goods) of SOLAS 74 and those of Annex III of the Maritime Pollution Convention (MARPOL 73/78). The IMDG Code has been developed and kept up to date for more than 30 years in close cooperation with the UN Committee of Experts on Transport of Dangerous Goods (CETG) and has been implemented by 50 IMO members representing 85% of the world’s merchant tonnage.

                    Harmonization of the IMDG Code with the UNRTDG ensures compatibility with the national and international rules applicable to the transport of dangerous goods by other modes, in so far as these other modal rules are also based on the recommendations of the UNCETG—that is, ICAO Technical Instructions for the Safe Transport of Dangerous Goods by Air and the European Regulations concerning the international carriage of dangerous goods by road (ADR) and by rail (RID).

                    In 1991 the 17th IMO Assembly adopted a Resolution on the Coordination of Work in Matters Relating to Dangerous Goods and Hazardous Substances, urging, inter alia, UN bodies and governments to coordinate their work in order to ensure the compatibility of any legislation on chemicals, dangerous goods and hazardous substances with established international transport rules.

                    Basel Convention on the Control of Transboundary Movements of Hazardous Wastes and their Disposal, 1989

                    The Convention’s Annexes define 47 categories of wastes, including domestic wastes. Although the hazard classification parallels that of the UNRTDG, a significant difference includes the addition of three categories reflecting more specifically the nature of toxic wastes: chronic toxicity, liberation of toxic gases from interaction of wastes with air or water, and capacity of wastes to yield secondary toxic material after disposal.


                    National classification systems related to the hazard assessment of pesticides tend to be quite comprehensive because of the wide use of these chemicals and the potential long-term damage to the environment. These systems may identify from two to five hazard classifications. The criteria are based on median lethal doses with different routes of exposure. While Venezuela and Poland recognize only one route of exposure, ingestion, the WHO and various other countries identify both ingestion and skin application.

                    The criteria for hazard assessment of pesticides in East European countries, Cyprus, Zimbabwe, China and others are based on median lethal doses via inhalation. Bulgaria’s criteria, however, include skin and eye irritation, sensitization, accumulation ability, persistence in environmental media, blastogenic and teratogenic effects, embryotoxicity, acute toxicity and medical treatment. Many classifications of pesticides also include separate criteria based on median lethal doses with different aggregative states. For example, criteria for liquid pesticides are usually more severe than those for solid ones.

                    WHO Recommended Classification of Pesticides by Hazard

                    This Classification was first issued in 1975 by the WHO and updated subsequently on a regular basis by the United Nations Environment Programme, the ILO and the WHO (UNEP/ILO/WHO) International Programme on Chemical Safety (IPCS) with input from the Food and Agriculture Organization (FAO). It consists of one hazard category or classification criterion, acute toxicity, divided in four classification levels based on LD50 (rat, oral and dermal values for liquid and solid forms) and ranging from extremely to slightly hazardous. Apart from general considerations, no specific labelling rules are provided. The 1996–97 update contains a guide to classification which includes a list of classified pesticides and comprehensive safety procedures. (See the chapter Minerals and agricultural chemicals.)

                    FAO International Code of Conduct on the Distribution and Use of Pesticides

                    The WHO Classification is supported by another document, the FAO International Code of Conduct on the Distribution and Use of Pesticides. Although it is only a recommendation, this classification is applied most widely in developing countries, where it is often included into pertinent national legislation. With regard to labelling, the FAO has published Guidelines on Good Labelling Practice for Pesticides as an addendum to these guidelines.

                    Regional Systems (EC, EFTA, CMEA)

                    The EC Council Directive 67/548/EEC has been in application for over two decades and has harmonized the pertinent legislation of 12 countries. It has evolved into a comprehensive system which includes an inventory of existing chemicals, a notification procedure for new chemicals prior to marketing, a set of hazard categories, classification criteria for each category, testing methods, and a hazard communication system including labelling with codified risk and safety phrases and hazard symbols. Chemical preparations (mixtures of chemicals) are regulated by Council Directive 88/379/EEC. The definition of the chemical safety data sheet data elements is practically identical to that defined in ILO Recommendation No. 177, as discussed earlier in this chapter. A set of classification criteria and a label for chemicals that are dangerous to the environment have been produced. The Directives regulate chemicals placed on the market, with the goal of protecting human health and the environment. Fourteen categories are divided into two groups related respectively to physico-chemical properties (explosive, oxidizing, extremely flammable, highly flammable, flammable) and toxicological properties (very toxic, toxic, harmful, corrosive, irritant, carcinogenic, mutagenic, toxic to reproduction, properties dangerous to health or the environment).

                    The Commission of European Communities (CEC) has an extension to the system specifically addressed to the workplace. In addition, these measures on chemicals should be considered within the overall framework of the protection of the health and safety of workers provided for under Directive 89/391/EEC and its individual Directives.

                    With the exception of Switzerland, the countries in EFTA follow the EC system to a large degree.

                    Former Council for Mutual Economic Assistance (CMEA)

                    This system was elaborated under the umbrella of the Standing Commission for Cooperation in Public Health of the CMEA, which included Poland, Hungary, Bulgaria, the former USSR, Mongolia, Cuba, Romania, Vietnam and Czechoslovakia. China still uses a system which is similar in concept. It consists of two classification categories, namely toxicity and hazard, using a four-level ranking scale. Another element of the CMEA system is its requirement for the preparation of a “toxicological passport of new chemical compounds subjected to introduction in the economy and domestic life”. Criteria for irritancy, allergic effects, sensitization, carcinogenicity, mutagenicity, teratogenicity, antifertility and ecological hazards are defined. However, the scientific basis and the testing methodology related to the classification criteria are significantly different from those used by the other systems.

                    Provisions for workplace labelling and hazard symbols are also different. The UNRTDG system is used for labelling goods for transport, but there does not seem to be any linkage between the two systems. There are no specific recommendations for chemical safety data sheets. The system is described in detail in the UNEP International Register of Potentially Toxic Chemicals (IRPTC) International Survey of Classification Systems. While the CMEA system contains most of the basic elements of the other classification systems, it differs significantly in the area of hazard assessment methodology, and uses exposure standards as one of the hazard classification criteria.

                    Examples of National Systems


                    Australia has enacted legislation for the notification and assessment of industrial chemicals, the Industrial Chemicals Notification and Assessment Act of 1989, with similar legislation enacted in 1992 for agricultural and veterinary chemicals. The Australian system is similar to that of the EC. The differences are mainly due to its utilization of the UNRTDG classification (i.e., the inclusion of the categories compressed gas, radioactive and miscellaneous).


                    The Workplace Hazardous Materials Information System (WHMIS) was implemented in 1988 by a combination of federal and provincial legislation designed to enforce the transfer of information about hazardous materials from producers, suppliers and importers to employers and in turn to workers. It applies to all industries and workplaces in Canada. WHMIS is a communication system aimed primarily at industrial chemicals and composed of three interrelated hazard communication elements: labels, chemical safety data sheets and worker education programmes. A valuable support to this system was the earlier creation and commercial distribution worldwide of a computerized database, now available on compact disc, containing over 70,000 chemical safety data sheets voluntarily submitted to the Canadian Centre for Occupational Health and Safety by manufacturers and suppliers.


                    In Japan, the control of chemicals is covered mainly by two laws. First, the Chemical Substances Control Law, as amended in 1987, is aimed at preventing environmental contamination by chemical substances that are low in biodegradability and harmful to human health. The law defines a premarket notification procedure and three “hazard” classes:

                      • Class 1—specified chemical substances (low biodegradation, high bioaccumulation, risk to human health)
                      • Class 2—specified chemical substances (low biodegradation and bioaccumulation, risk to human health and of contamination of the environment in vast areas)
                      • Class 3—designated substances (low biodegradation and bioaccumulation, suspicion of risk to human health)


                          Control measures are defined, and a list of existing chemicals is provided.

                          The second regulation, the Industrial Safety and Health Law, is a parallel system with its own list of “Specified chemical substances” which require labelling. Chemicals are classified into four groups (lead, tetraalkyl lead, organic solvents, specified chemical substances). The classification criteria are (1) possible occurrence of serious health impairment, (2) possible frequent occurrence of health impairment and (3) actual health impairment. Other laws dealing with the control of hazardous chemicals include the Explosives Control Law; the High Pressure Gas Control Law; the Fire Prevention Law; the Food Sanitation Law; and the Drugs, Cosmetics and Medical Instruments Law.

                          United States

                          The Hazard Communication Standard (HCS), a mandatory standard promulgated by OSHA, is a workplace-oriented binding regulation which refers to other existing laws. Its goal is to ensure that all chemicals produced or imported are evaluated, and that information related to their hazards is transmitted to employers and to workers through a comprehensive hazard communication programme. The programme includes labelling and other forms of warning, chemical safety data sheets and training. Label and data sheet minimum contents are defined, but the use of hazard symbols is not mandatory.

                          Under the Toxic Substances Control Act (TSCA), administered by the Environmental Protection Agency (EPA), an inventory listing approximately 70,000 existing chemicals is maintained. The EPA is developing regulations to complement the OSHA HCS which would have similar hazard evaluation and worker communication requirements for the environmental hazards of chemicals on the inventory. Under TSCA, prior to manufacture or import of chemicals which are not on the inventory, the manufacturer must submit a premanufacture notice. The EPA may impose testing or other requirements based on the premanufacture notice review. As new chemicals are introduced into commerce, they are added to the inventory.


                          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.

                          Labelling consists of phrases as well as graphic and colour symbols applied directly on the product, package, label or tag. The marking should be clear, easily comprehensible and able to withstand adverse climatic conditions. The labelling should be placed against a background that contrasts with the product’s accompanying data or package colour. The MSDS provides more detailed information on the nature of the chemical product’s hazards and the appropriate safety instructions.

                          While presently there are no globally harmonized labelling requirements, there are established international, national and regional regulations for labelling hazardous substances. Requirements for labelling are incorporated into the Law on Chemicals (Finland), the Act on Dangerous Products (Canada) and EC Directive N 67/548. Minimum label content requirements of the European Union, United States and Canadian systems are relatively similar.

                          Several international organizations have established labelling content requirements for handling chemicals at the workplace and in transport. The labels, hazard symbols, risk and safety phrases, and emergency codes of the International Organization for Standardization (ISO), the UNRTDG, the ILO and EU are discussed below.

                          The section on labelling in the ISO/IEC guide 51, Guidelines for Inclusion of Safety Aspects in Standards, includes commonly recognized pictograms (drawing, colour, sign). In addition, short and plain warning phrases alert the user to potential hazards and provide information on preventive safety and health measures.

                          The guidelines recommend the use of the following “signal” words to alert the user:

                            • DANGER—high danger
                            • HANDLE WITH CARE—intermediate danger
                            • BEWARE—potential danger.


                                The UNRTDG establish five main pictograms for easy visible recognition of dangerous goods and significant hazard identification:

                                  • bomb—explosive
                                  • flame—flammable
                                  • skull and cross-bones—toxic
                                  • trefoil—radioactive
                                  • liquid pouring out of two test-tubes on a hand and a piece of metal—corrosive.


                                  These symbols are supplemented by other representations such as:

                                    • oxidizing substances—flame above a circle
                                    • non-flammable gases—a gas bottle
                                    • infectious substances—three crescent signs superimposed on a circle
                                    • harmful substances which should be stowed away—St. Andrew’s cross posed on a wheat-ear.


                                          The Chemicals Convention, 1990 (No. 170), and Recommendation, 1990 (No. 177), were adopted at the 77th Session of the International Labour Conference (ILC). They establish requirements for the labelling of chemicals to ensure the communication of basic hazard information. The Convention states that label information should be easily understandable and should convey the potential risks and appropriate precautionary measures to the user. Regarding the transport of dangerous goods, the Convention refers to the UNRTDG.

                                          The Recommendation outlines labelling requirements in accordance with existing national and international systems, and establishes criteria for classification of chemicals including chemical and physical properties; toxicity; necrotic and irritating properties; and allergic, teratogenic, mutagenic and reproductive effects.

                                          The EC Council Directive N 67/548 stipulates the form of label information: graphic hazard symbols and pictograms including risk and safety phrases. Hazards are coded by the Latin letter R accompanied with combinations of Arabic numerals from 1 to 59. For example, R10 corresponds with “flammable”, R23 with “toxic by inhalation”. The hazard code is given with a safety code consisting of the Latin letter S and combinations of numerals from 1 to 60. For example, S39 means “Wear eye/face protection”. The EC labelling requirements serve as a reference for chemical and pharmaceutical companies throughout the world.

                                          Despite significant efforts in chemical hazard data acquisition, evaluation and organization by different international and regional organizations, there is still a lack of coordination of these efforts, particularly in the standardization of assessment protocols and methods and interpretation of data. The ILO, the Organization for Economic Cooperation and Development (OECD), the IPCS and other concerned bodies have initiated a number of international activities aimed toward establishing a global harmonization of chemical classification and labelling systems. The establishment of an international structure to monitor chemical hazard assessment activities would greatly benefit workers, the general public and the environment. An ideal harmonization process would reconcile the transport, marketing and workplace classification and labelling of hazardous substances, and address consumer, worker and environmental concerns.



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