thinking” to characterize where a particular product, action, or decision may shift effects somewhere in the life cycle of a product or activity and how those effects can be minimized or prevented. For example, a simple chemical substitution may result in the use of a new product that may be safer for consumers but may cause effects on workers far upstream in the production process. In addition, LCA is an inherently comparative tool because it considers the life-cycle implications of multiple products or processes that achieve the same end use. This so-called functional unit determination is intended to be broad and to encourage innovation in the development of solutions by focusing on what a consumer needs from a product rather than on the product itself. Box 4-3 outlines the opportunities that LCA or life-cycle thinking can provide to enhance systems thinking about complex problems.

Cumulative Risk Assessment

The advent of new science tools and techniques means that the suite of traditional tools need to be reviewed and enhanced for 21st century challenges and opportunities. Quantitative risk assessment has been central to many aspects of EPA’s mission for decades. The risk-based decision-making framework proposed in Science and Decisions: Advancing Risk Assessment (NRC 2009) offers an opportunity, and detailed recommendations, for the agency to revisit and revamp its current practices. In particular, this would encourage linkages between risk assessment and various solutions-oriented approaches. In addition, as discussed in Chapter 3, a host of rapidly evolving health and ecosystem assessment tools (for example, “-omics” and the exposome) can be applied, with appropriate deliberation, to enhance risk assessment further.

Beyond enhancements in traditional single-chemical risk assessment, many of the trends in both science and risk-assessment practice in recent years involve moving from a single-chemical perspective to a multistressor perspective. EPA has grappled with chemical mixtures for some time, and cumulative risk assessment has come to the forefront of the agency’s thinking over the last decade, although the agency has rarely used it. Multiple recent NRC committees have addressed cumulative risk assessment extensively (NRC 2008, 2009), and the present committee concurs with the prior recommendations. Moreover, the committee supports the growing emphasis in EPA on this topic (which includes both intramural and extramural research), noting that these efforts have increasingly emphasized community-based participatory approaches, applications in disadvantaged communities, and use of epidemiologic insight. Nonetheless, although much of the emphasis of previous NRC reports has been on cumulative risk assessment for human health effects, it is possible that insights and approaches from ecosystem-based cumulative impact analyses (required under the National Environmental Policy Act [NEPA]) could be adapted to cumulative risk assessment for human health effects.

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