Printed Wiring Board Industry: Part 2 - 4 Selecting A Use Cluster for a DfE Project
A. Cleaner Technologies Substitutes Assessment
In a DfE pwb project, a use cluster is selected to become the focus of a Cleaner Technologies Substitutes Assessment (CTSA). The CTSA is a flexible format for systematically comparing trade-off issues associated with traditional and alternative chemicals, processes, and technologies. For each chemical, process, or technology, the cost, performance, environmental and health risks, environmental releases, energy impacts, and resource conservation implications are evaluated. The goal of the CTSA is to allow for an informed decision about which alternative is best for a particular situation.
B. Use Cluster Scoring System
EPA's Office of Pollution Prevention and Toxics (OPPT) has developed a system for use in screening and prioritizing use clusters, referred to as the Use Cluster Scoring System (UCSS). The UCSS was designed around the concept of identifying and analyzing clusters of chemicals that can be used to perform a particular task, such as those described in this report. By screening and scoring these "use clusters," efforts may be more directly focused upon effective risk reduction through work with targeted industries or users. The UCSS also assists other public and private sector organizations to identify clusters of potential concern and provide an initial ranking of chemicals using hazard and exposure data from various sources.
Data is first collected for each chemical within a cluster for a number of factors that indicate the potential for human and environmental exposure, potential for human and environmental hazard, pollution prevention potential, and EPA/stakeholder interest. This information is then entered in the UCSS using the data entry menu options.
Health and environmental risk or toxicity rating scores are calculated for each chemical within a cluster using the information entered and pre-programmed scoring algorithms. The individual chemical scores are then used to calculate an overall cluster score, which is an indicator of potential risk and pollution prevention potential for the use cluster. OPPT uses this risk score to prioritize clusters to be investigated in more detail.
C. Use Cluster Selection in the DfE PWB Project
At the beginning of the DfE PWB Project, four use clusters were defined by industry stakeholders as being of high priority for evaluation in a CTSA. The four use clusters were:
- Inner layer etching
- Outer layer etching and plating
- Making holes conductive
- Hot air solder leveling
These four use clusters were evaluated by EPA for their potential environmental risk and pollution prevention potential using the UCSS. The lowest possible score (least risk) is 4 and the highest possible score (greatest risk) is 24. The scores for each use cluster were:
- Inner layer etching 12.3
- Outer layer etching and plating 12.7
- Making holes conductive 11.2
- Hot air solder leveling 12.1
It was determined that there is no statistical difference between these scores; all fall in the "medium" range. That is, they have the potential to pose moderate risk to both humans and the environment. Use cluster scores are one of several criteria that are considered in the selection of a use cluster. The similarity in the scores, however, led to an increased emphasis on other criteria in making the selection for the PWB Project.
Because the objective of the CTSA is to evaluate alternatives, it is very important to select a use cluster with several viable alternatives. Other criteria, such as occupational health risk, industry interest, and regulatory cost/burden, should also be considered.
The first use cluster selected for evaluation in the DfE PWB Project was making holes conductive. Ten alternatives, the greatest number found for any of the potential use clusters, were identified for this cluster during the information gathering phase of the project. Also, the project participants believed that there were a number of relatively easily addressed environmental issues associated with the making holes conductive use cluster. Another reason that making holes conductive is a good initial use cluster for a CTSA is that some of the alternatives promise production rate benefits. The processes could be conveyerized, the production cycles could be decreased, the pre-treatment rinses could be simplified, and waste production could be reduced. In addition, simple pollution prevention practices could be implemented in the baths. While information is being gathered about new and emerging technologies, some of the current processes are undergoing revision and enhancements. The CTSA is a convenient place to assess these enhancements.
D. Future Design for the Environment Projects
This profile document has already served its original purpose in assisting the Design for the Environment PWB Project to select the first use cluster for further analysis in a CTSA. It is anticipated that the profile document will be useful in future Design for the Environment Project activities and to other interested parties wishing to use this information for their own analyses.