and repair operations (Holusha, 1996). The expense and initial difficulties of recycling plastic enclosures and other parts of electronic products have been addressed by simple strategies, like minimizing the diversity of plastics used and by clearly marking plastics in terms of several classifications of the material. When materials are carefully selected with reuse and recycling in mind, it is easier to create cost-effective (and sometimes profitable) relationships with recyclers and material vendors, to whom businesses might sell recovered materials. Such practices can also be useful in meeting government procurement requirements, which in many areas mandate the percentages of recycled materials that products should contain.
Chemical-use evaluations can be important in assuring that hazardous materials are not used in products and in identifying potential chemical-related problems early enough in design so that the product and process used for manufacture can be reengineered. Simple tools, such as checklists, can be effective in evaluating many materials. Recently, more systematic approaches such as life cycle assessments (LCA) are being used to guide materials use decisions.
LCAs are intended to evaluate the environmental impacts of products at every stage, from raw material extraction and production through distribution and disposal. They generally consist of three distinct but interrelated components:
Life cycle inventory, an input-output accounting that quantifies the inputs of energy and raw materials and outputs of products, air emissions, water borne effluent, solid waste, and other environmental releases associated with the entire life cycle of the product, process, or activity.
Life cycle impact analysis, a characterization of the effects of the environmental loadings identified in the life cycle inventory and an assessment of the loadings in terms of ecological and human health impacts.
Life cycle improvement analysis, a systematic evaluation of the needs and opportunities to reduce the environmental burden associated with impacts of the inputs and outputs that have been inventoried and analyzed.
There are problems with LCA (Johnson, this volume). LCA is methodologically and analytically complex; creates the false impression that it includes everything; is data- and resource-intensive; neglects qualitative and unquantifiable factors; and frequently uses inadequate ''surrogates" for environmental impacts. Furthermore, LCA has the potential for "paralysis by analysis," if the boundaries of the analysis are not well defined. In evaluating two products, it is reasonable to examine the raw materials used to make them. But, should the energy used to make the machinery used to extract the raw materials be included as well? Should the type, age, and efficiency of the machinery used to make the product be considered? And should the source of electricity be tracked back to it fossil, hydro, gas, or solar origins? LCA also is of little help for assessing the realistic impacts of pollution that often depend on time and location of occurrence. For example,