Classification of hazardous substances

As noted in the Classification of hazardous substances and mixtures (see Chapter 1.3), there may be some cases when the available hazard data may justify classification on the basis of other cut-off values/concentration limits than the generic ones specified in the health and environment hazard class chapters (Chapters 3.2 to 3.10 and 4.1). When such specific cut-off values are used for classification, they should also apply to the obligation to compile an SDS. 

If there are data showing that (an) ingredient(s) may be corrosive or irritant at a concentration of < 1% (corrosive) or < 3% (irritant), the mixture should be classified accordingly (see also Classification of hazardous substances and mixtures - Use of cut-off values/Concentration limits (1.3.3.2)). 

Classification of hazardous substances and their associated health risks... 

Space 3 Hazard warning sign for the classification of the substance as specified in Part 1 of the approved list Space 4 Telephone number where expert advice can be obtained at all times when the substance is being conveyed by road... 

Space 3 Hazard warning sign for the classification of the substance as specified in Part I of the approved list... 

The criteria and procedural methods for characterising substances with regard to their hazardous characteristics and risk characterisation are harmonised in Europe. There also exists a common European system for the classification and labelhng of hazardous substances and for safety data sheets. Officially harmonised classifications also exist for around 3000 substances. The individual elements of the current system as well as its weaknesses are to be explained in the following section. 

Second, waste that contains hazardous substances is classified based on considerations of health risks to the public that arise from waste disposal. The existing classification systems for radioactive and chemical wastes in the United States are not based primarily on considerations of health risks to the public. Rather, classification of hazardous wastes has been based primarily on the source of the waste or the presence of particular hazardous substances. The absence of risk-based waste classifications has had a number of undesirable ramifications ... 

This Report presents the foundations and technical principles for development of a generally applicable and risk-based hazardous waste classification system. Recommendations on suitable approaches to establishing boundaries of different waste classes are discussed these boundaries could be expressed, for example, in terms of limits on concentrations of hazardous substances. However, a particular implementation of the proposed waste classification system in terms of quantifying the boundaries of different waste classes is not presented. 

Thus, the basic elements of the proposed classification system are, first, that there should be a general class of waste that contains sufficiently small concentrations of radionuclides or hazardous chemicals that it can be exempted from regulatory control as hazardous material and, second, that there should be two classes of nonexempt waste that contain increasing concentrations of hazardous substances and require dedicated disposal systems that provide increased waste isolation. 

The recommendations on waste classification should focus on concepts, principles, and approaches to implementation. Recommendations on approaches to using assumed limits on risk or dose to establish quantitative boundaries of waste classes expressed as limits on concentrations of hazardous substances would be presented, and precedents that could be used to define the assumed limits on risk or dose and to assess risk or dose for purposes of waste classification would be discussed. However, specific recommendations on values of any such limits and many of the considerations involved in establishing them would not be given, because this is properly the role of policy makers and regulatory authorities. 

Risk Index for Mixtures of Hazardous Substances. For the purpose of developing a comprehensive and risk-based hazardous waste classification system, a simple method of calculating the risk posed by mixtures of radionuclides and hazardous chemicals is needed. The method should account for the linear, nonthreshold dose-response relationships for radionuclides and chemical carcinogens (stochastic effects) and the threshold dose-response relationships for noncarcinogenic hazardous chemicals (deterministic effects). 

NCRP believes that a conceptually simple composite risk index for mixtures of hazardous substances can be developed that provides an adequate representation of risk for the purpose of waste classification. The composite risk index is written in terms of separate risk indexes for substances that induce stochastic (s) and deterministic (d) effects as ... 

A general class of exempt waste, which could be regulated as nonhazardous material, would be established. Development of an exempt class of waste that contains low levels of hazardous substances has been controversial and currently is banned by law in the case of radioactive waste. Some radioactive and hazardous chemical wastes have been exempted on a case-by-case basis, but general principles for exempting radioactive or hazardous chemical wastes have not been established. In spite of these difficulties, however, a meaningful risk-based waste classification system must include a general class of exempt waste. 

For many wastes, there is no practical classification system for establishing a boundary (e.g., amount of hazardous substances) below which the waste is considered to be nonhazardous. This means that large volumes of waste are managed at considerable cost because the waste cannot be conclusively shown to contain no hazardous substances or, even more difficult, to contain an amount of hazardous substances e.g., uranium) no greater than was initially present in a material before its use by humans. 

DOE s high-level wastes as if they were among the most hazardous of all radioactive wastes. However, the concentrations of hazardous substances in some of these wastes are similar to those in low-level radioactive waste that is normally intended for disposal in near-surface facilities. In contrast, some chemical wastes that are highly hazardous, compared with other wastes, and nondegradable are being sent to near-surface disposal facilities. Both of these situations occur largely because of the source-based aspects of existing waste classification systems. 

The waste classification system developed in this Report includes a general class of exempt waste. Waste in this class would contain sufficiently small amounts of hazardous substances that it could be managed in all respects as if it were nonhazardous (e.g., as household trash). NCRP intends that exempt materials could be used or disposed of in any manner allowed by laws and regulations addressing disposition of nonhazardous materials. However, exempt waste would not necessarily be exempt for purposes of beneficial use without further analysis of the risks associated with anticipated uses. Materials could be exempted for purposes of disposal or beneficial use based on similar considerations of acceptable risk. However, based on differences in exposure scenarios for the two dispositions, limits on the amounts of hazardous substances that could be present in exempt materials intended for beneficial use could be substantially lower than the limits for disposal as exempt waste. Thus, disposal may be the only allowable disposition for some exempt materials based on considerations of risk. In addition, some exempt materials may consist of trash, rubble, and residues from industrial processes that would have no beneficial uses and must be managed as waste. 

This Report culminates in the presentation of the principles and framework for a comprehensive and risk-based hazardous waste classification system. NCRP does not propose a particular implementation of the proposed classification system (e.g., a particular quantification in terms of limits on concentrations of hazardous substances in each waste class) this is most appropriately left to governmental policy organizations. The relationship of the proposed risk-based waste classification system to existing regulations is discussed in Section 7.2. 

Thus, for purposes of waste classification, it appears possible to assess the risk from the intrusion and atmospheric release pathways at a generic hazardous waste disposal site. However, a generic assessment of risk from the water release pathway normally would incorporate assumptions that would be extremely conservative for many sites (e.g., the amount of water infiltration and travel times of hazardous substances to a nearby well). 

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