William S. Pease

Evaluating the environmental impact of products and production processes: a comparison of six methods

The desire of environmentally-conscious consumers and manufacturers to choose more environmentally benign products and processes has led to the development of life cycle assessment (LCA) and design for environment (DfE). In both of these areas, attention has focused initially on the development of inventories of emissions and raw materials consumption for particular products and processes. A number of methods for the comparison and evaluation of an inventorys dissimilar pollution loads and resource demands have been proposed, but no satisfactory solution has yet been identified. This paper compares the structure and properties of six different methods. The health hazard scoring (HHS) system uses the analytical hierarchy process (AHP) to weight workplace toxic effects and accident risks. The material input per service-unit (MIPS) aggregates the mass of all the material input required to produce a product or service. The Swiss eco-point (SEP) method scores pollutant loadings based on a sources contribution to an acceptable total pollution load and an environmental scarcity factor. The sustainable process index (SPI) determines the area that would be required to operate a process sustainably, based on renewable resource generation and toxic degradation; an extension of the dilution volume approach. The Society of Environmental Toxicology and Chemistrys life-cycle impact assessment (SETAC LCA) impact assessment method aggregates pollutants with similar impacts to equivalency potentials (measured in kg CO2 equivalent, kg benzene equivalent etc.) and uses decision analysis to assign weights to different adverse impacts. The environmental priority system (EPS) characterizes the environmental damage caused by equivalency potentials and expresses it in monetary terms, derived from environmental economics. Despite their use for the same purposes, the six methods differ in what they try to achieve, in the effects they consider, in the depth of analysis, in the way values influence the final score, and in use of ordinal or cardinal measures of impact. Two problem areas are identified: (1) to varying degrees, each of the methods has the potential to recommend an alternative that actually has a higher impact than other alternatives; (2) for some of the methods the data requirement is so extensive and the tolerance of imperfect data is so low that the application of the method for reasonably sophisticated products or processes would be too complicated.

Parameter Uncertainty and Variability In Evaluative Fate and Exposure Models

The human toxicity potential, a weighting scheme used to evaluate toxic emissions for life cycle assessment and toxics release inventories, is based on potential dose calculations and toxicity factors. This paper evaluates the variance in potential dose calculations that can be attributed to the uncertainty in chemical-specific input parameters as well as the variability in exposure factors and landscape parameters. A knowledge of the uncertainty allows us to assess the robustness of a decision based on the toxicity potential; a knowledge of the sources of uncertainty allows us to focus our resources if we want to reduce the uncertainty. The potential dose of 236 chemicals was assessed. The chemicals were grouped by dominant exposure route, and a Monte Carlo analysis was conducted for one representative chemical in each group. The variance is typically one to two orders of magnitude. For comparison, the point estimates in potential dose for 236 chemicals span ten orders of magnitude. Most of the variance in the potential dose is due to chemical-specific input parameters, especially half-lives, although exposure factors such as fish intake and the source of drinking water can be important for chemicals whose dominant exposure is through indirect routes. Landscape characteristics are generally of minor importance.

A Theoretical Foundation for Life‐Cycle Assessment

Summary The presence of value judgments in life-cycle impact assessment (LCIA) has been a constant source of controversy. According to a common interpretation, the international standard on LCIA requires that the assessment methods used in published comparisons be “value free.” Epistemologists argue that even natural science rests on “constitutive” and “contextual” value judgments. The example of the equivalency potential for climate change, the global warming potential (GWP), demonstrates that any impact assessment method inevitably contains not only constitutive and contextual values, but also preference values. Hence, neither life-cycle assessment (LCA) as a whole nor any of its steps can be “value free.” As a result, we suggest a more comprehensive definition of objectivity in LCA that allows arguments about values and their relationship to facts. We distinguish three types of truth claims: factual claims, which are based on natural science; normative claims, which refer to preference values; and relational claims, which address the proper relation between factual knowledge and values. Every assessment method, even the GWP, requires each type of claim. Rational arguments can be made about each type of claim. Factual truth claims can be assessed using the scientific method. Normative claims can be based on ethical arguments. The values of individuals or groups can be elicited using various social science methods. Relational claims must follow the rules of logic. Relational claims are most important for the development of impact assessment methods. Because LCAs are conducted to satisfy the need of decision makers to consider environmental impacts, relational claims about impact assessment methods should refer to this goal. This article introduces conditions that affect environmental decision making and discusses how LCA—values and all—can be defended as a rational response to the challenge of moving uncertain scientific information into the policy arena.

A Systematic Uncertainty Analysis of an Evaluative Fate and Exposure Model

Multimedia fate and exposure models are widely used to regulate the release of toxic chemicals, to set cleanup standards for contaminated sites, and to evaluate emissions in life-cycle assessment. CalTOX, one of these models, is used to calculate the potential dose, an outcome that is combined with the toxicity of the chemical to determine the Human Toxicity Potential (HTP), used to aggregate and compare emissions. The comprehensive assessment of the uncertainty in the potential dose calculation in this article serves to provide the information necessary to evaluate the reliability of decisions based on the HTP A framework for uncertainty analysis in multimedia risk assessment is proposed and evaluated with four types of uncertainty. Parameter uncertainty is assessed through Monte Carlo analysis. The variability in landscape parameters is assessed through a comparison of potential dose calculations for different regions in the United States. Decision rule uncertainty is explored through a comparison of the HTP values under open and closed system boundaries. Model uncertainty is evaluated through two case studies, one using alternative formulations for calculating the plant concentration and the other testing the steady state assumption for wet deposition. This investigation shows that steady state conditions for the removal of chemicals from the atmosphere are not appropriate and result in an underestimate of the potential dose for 25% of the 336 chemicals evaluated.

Environmental policy analysis: evaluating toxic impact assessment methods: what works best.

EDGAR G. HERTWICH Energy and Resources Group University of California Berkeley, CA 94720-3050 WILLIAM S. PEASE Environmental Defense Fund Oakland, CA 95616 THOMAS E. MCKONE Environmental Health Science University of California Berkeley, CA 94720-7360.

From health-based to technology-based standards for hazardous air pollutants.

The Clean Air Act Amendments of 1990 represent a major shift in regulatory emphasis for toxic air pollutants. Recognizing the immediate public health benefits that can be gained from the application of currently available and affordable control technologies, Congress has abandoned its insistence that health risks should be the only consideration in establishing emissions standards. Previously excluded concerns about economic costs and technological feasibility will now determine the initial level of pollution control required of toxic air pollution sources. In exchange for reducing the stringency of emissions limits, the newly amended act extends the scope of regulation by listing 189 toxic substances that must be controlled over the next decade. This exchange of regulatory depth for breadth occurs against a history of reluctance by the Environmental Protection Agency to implement the original health-protective language of the Clean Air Act. It mirrors earlier compromises under the Clean Water Act and the Occupational Safety and Health Act.

Hazard and risk-based approaches to comparing toxic emissions

Comparison of the environmental impacts of chemicals, production processes, products, or companies requires methods to interpret emissions data contained in DFE evaluations, life cycle inventories, and toxics release inventories. Impact evaluation methods for toxic substances range from simple toxicity scoring to sophisticated risk-based models. This paper explains two such methods. The environmental impact matrix approach is based on a categorical hazard identification. As a qualitative assessment, it is fairly simple to conduct. It has been used by the Source Reduction Research Partnership to evaluate alternatives to chlorinated solvents. The Human Toxicity Potential (HTP) is based on a multi-pathway environmental exposure model and uses extensive toxicity data. The Dutch government recommended its use in life cycle analysis, along with other equivalency scores, e.g. for global warming, ozone depletion, and smog generation. The steps necessary to calculate an HTP score using the CalTOX model are presented and data needs as well as underlying assumptions are discussed. Differences between the simple scoring mechanism and HTP are illuminated through an example.