Hazardous chemicals, replacement

Hazardous chemicals or mixtures may be replaceable by safer materials. These may be less toxic per se, or less easily dispersed (e.g. less volatile or dusty). Substitution is also applicable to synthesis routes to avoid the use of toxic reactants/solvents or the production, either intentionally or accidentally, of toxic intermediates, by-products or wastes. 

Wherever practicable it is advisable for glutaraldehyde to be replaced by a less hazardous chemical, e.g. it should not be used as a general wipe-down disinfectant. 

In many cases, it is possible to replace environmentally hazardous chemicals with more benign species without compromising the technical and economic performance of the process. Examples include alternative solvents, polymers, and refrigerants. Group contribution methods have been conunonly used in predicting physical and chemical properties of synthesized materials. Two main frameworks have... 

It provides a stimulus and direction for innovation. Governments need not prescribe particular alternatives, but rather define criteria to guide the identification of alternatives. This will end the common practice of replacing a hazardous chemical under legislative pressure with a similar hazardous chemical that is less in the spotlight. 

In applying paragraph 1, substitution shall by preference be undertaken, whereby the employer shall avoid the use of a hazardous chemical agent by replacing it with a chemical agent or process which, under its condition of use, is not hazardous or less hazardous to workers health and safety, as the case may be. 

As a first step substances that are known to cause problems in the wastewater have to be replaced by less hazardous chemicals or the process itself should be reconsidered for example,... 

Under the conditions of the 1976 Resource Conservation and Recovery Act (RCRA), the Environmental Protection Agency focuses its efforts in dealing with hazardous wastes on 30 hazardous chemicals of special importance. Those chemicals are called waste minimization priority chemicals (WMPC). The list of WMPC, shown in the chart on page 160, changes over time, reflecting success in reducing the amount of one or another chemical in the environment, the ability to remove that chemical from the list, and the replacement of that chemical by another of environmental importance. 

The amount of hazardous chemicals on-site can be reduced by methods other than altering the scale of production. For example, the amount of hazardous material stored on-site can often be significantly reduced, and if not, the hazardous materials can be stored in many small containers in separate facilities rather than in a single container. Therefore, if a container fails, the size and catastrophic potential of the release are much reduced. In addition, the amount of material needed in the production process can be reduced by using specially designed equipment (such as Higee columns, which replace conventional distillation columns). 

An obvious method for increasing the inherent safety of a production process is to substitute safer chemicals for more hazardous chemicals wherever possible. For example, flammable chemicals might be replaced by nonflammable chemicals explosive chemicals might be replaced by less reactive chemicals and highly toxic chemicals might be replaced by less toxic chemicals. 

The hazardous waste classification system recommended by NCRP is depicted in Figure 6.1 at the beginning of Section 6. This proposal was developed with two fundamental objectives in mind. First, all wastes that contain radionuclides, hazardous chemicals, or mixtures of the two should be included in the same classification system. A comprehensive hazardous waste classification system should be developed to replace the separate, and quite different, classification systems for radioactive and hazardous chemical wastes, as well as the separate classification systems for radioactive waste that arises from operations of the nuclear fuel cycle and NARM waste. Second, all hazardous wastes should be classified based on considerations of risks to the public that arise from disposition of the material. In this Report, permanent disposal in a permitted facility for hazardous or nonhazardous waste is the assumed disposition of waste containing hazardous substances that has no further use to its present custodian. An important consequence of these two objectives is that the same rules should apply in classifying any waste that contains hazardous substances. 

Ravetti, F. The role of dimethylcarbonate in the replacement of hazardous chemicals. Surf. Chem. Catal. 2000, 3, 497-503. 

The replacement of hazardous chemicals with benign and inherently safer alternatives indicated by green chemistry principles is certainly a valuable measure, because a hazardous chemical that is no longer present can no longer be involved in an accident. However, from industrial point of view there are often alternative solution that reduce the risk to a sustainable level at a much lower cost than that required by completely changing the production. 

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