In 2005, a comprehensive comparison of life cycle impact assessment toxicity characterisation models was initiated by the United Nations Environment Program (UNEP)–Society for Environmental Toxicology and Chemistry (SETAC) Life Cycle Initiative, directly involving the model developers of CalTOX, IMPACT 2002, USES-LCA, BETR, EDIP, WATSON and EcoSense. In this paper, we describe this model comparison process and its results—in particular the scientific consensus model developed by the model developers. The main objectives of this effort were (1) to identify specific sources of differences between the models’ results and structure, (2) to detect the indispensable model components and (3) to build a scientific consensus model from them, representing recommended practice. A chemical test set of 45 organics covering a wide range of property combinations was selected for this purpose. All models used this set. In three workshops, the model comparison participants identified key fate, exposure and effect issues via comparison of the final characterisation factors and selected intermediate outputs for fate, human exposure and toxic effects for the test set applied to all models. Through this process, we were able to reduce inter-model variation from an initial range of up to 13 orders of magnitude down to no more than two orders of magnitude for any substance. This led to the development of USEtox, a scientific consensus model that contains only the most influential model elements. These were, for example, process formulations accounting for intermittent rain, defining a closed or open system environment or nesting an urban box in a continental box. The precision of the new characterisation factors (CFs) is within a factor of 100–1,000 for human health and 10–100 for freshwater ecotoxicity of all other models compared to 12 orders of magnitude variation between the CFs of each model, respectively. The achieved reduction of inter-model variability by up to 11 orders of magnitude is a significant improvement. USEtox provides a parsimonious and transparent tool for human health and ecosystem CF estimates. Based on a referenced database, it has now been used to calculate CFs for several thousand substances and forms the basis of the recommendations from UNEP-SETAC’s Life Cycle Initiative regarding characterisation of toxic impacts in life cycle assessment. We provide both recommended and interim (not recommended and to be used with caution) characterisation factors for human health and freshwater ecotoxicity impacts. After a process of consensus building among stakeholders on a broad scale as well as several improvements regarding a wider and easier applicability of the model, USEtox will become available to practitioners for the calculation of further CFs.

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USEtox—the UNEP-SETAC toxicity model: recommended characterisation factors for human toxicity and freshwater ecotoxicity in life cycle impact assessment

Health risks of heavy metals to the general public in Tianjin, China via consumption of vegetables and fish.

At the request of the U.S. Environmental Protection Agency (EPA), the National Research Council (NRC) recently completed a major report, Science and Decisions: Advancing Risk Assessment, that is intended to strengthen the scientific basis, credibility, and effectiveness of risk assessment practices and subsequent risk management decisions. The report describes the challenges faced by risk assessment and the need to consider improvements in both the technical analyses of risk assessments (i.e., the development and use of scientific information to improve risk characterization) and the utility of risk assessments (i.e., making assessments more relevant and useful for risk management decisions). The report tackles a number of topics relating to improvements in the process, including the design and framing of risk assessments, uncertainty and variability characterization, selection and use of defaults, unification of cancer and noncancer dose-response assessment, cumulative risk assessment, and the need to increase EPA's capacity to address these improvements. This article describes and summarizes the NRC report, with an eye toward its implications for risk assessment practices at EPA.

Science and decisions: advancing risk assessment.

Background: At a time of increasing disconnectedness from nature, scientific interest in the potential health benefits of nature contact has grown. Research in recent decades has yielded substantia...

https://www.fs.fed.us/pnw/pubs/journals/pnw_2017_frumkin001.pdf

Nature Contact and Human Health: A Research Agenda

This study presents concurrently sampled ambient air data for a range of persistent organic pollutants at the continental scale. This was achieved using a passive air sampling system, deploying polyurethane foam disks, which was prepared in one laboratory, sealed to prevent contamination, sent out by courier to volunteers participating in different countries, exposed for 6 weeks, collected, re-sealed, and returned to the laboratory for analysis. Europe was the study areaa region with a history of extensive POPs usage and emission and with marked national differences in population density, the degree of urbanization and industrial/agricultural development. Samplers were deployed at remote/rural/urban locations in 22 countries and analyzed for PCBs, a range of organochlorine pesticides (HCB, α-HCH, γ-HCH, ppDDT, ppDDE), and PBDEs. Calculated air concentrations were in line with those obtained by conventional active air sampling techniques. The geographical pattern of all compounds reflected suspected region...

Passive Air Sampling of PCBs, PBDEs, and Organochlorine Pesticides Across Europe

We present the Berkeley-Trent North American contaminant fate model (BETR North America), a regionally segmented multimedia contaminant fate model based on the fugacity concept. The model is built on a framework that links contaminant fate models of individual regions, and is generally applicable to large, spatially heterogeneous areas. The North American environment is modeled as 24 ecological regions, within each region contaminant fate is described using a 7 compartment multimedia fugacity model including a vertically segmented atmosphere, freshwater, freshwater sediment, soil, coastal water and vegetation compartments. Inter-regional transport of contaminants in the atmosphere, freshwater and coastal water is described using a database of hydrological and meteorological data compiled with Geographical Information Systems (GIS) techniques. Steady-state and dynamic solutions to the 168 mass balance equations that make up the linked model for North America are discussed, and an illustrative case study of toxaphene transport from the southern United States to the Great Lakes Basin is presented. Regionally segmented models such as BETR North America can provide a critical link between evaluative models of long-range transport potential and contaminant concentrations observed in remote regions. The continent-scale mass balance calculated by the model provides a sound basis for evaluating long-range transport potential of organic pollutants, and formulation of continent-scale management and regulatory strategies for chemicals.

BETR North America: A regionally segmented multimedia contaminant fate model for North America

The International Society for Exposure Analysis (ISEA) and its Nomenclature Committee have been involved since the mid-1990s in an intermittent but ongoing effort to develop an official ISEA glossary. Several related activities have stimulated greater interest and discussion nationally and internationally on a common exposure language. Among these activities are a 1997 Journal of Exposure Analysis and Environmental Epidemiology feature article on exposure and dose definitions and a 1999-initiated project of the International Programme on Chemical Safety (IPCS) (WHO/ILO/UNEP) to confront terminology issues hindering harmonization in the area of exposure assessment. Recently, the ISEA members voted in support of adopting the IPCS glossary as the official ISEA glossary, and the ISEA Executive Board agreed to accept this recommendation. In this feature article, we (1) describe the process through which the ISEA adopted the IPCS glossary as the official ISEA glossary, (2) present the joint IPCS/ISEA glossary of terms and their definitions, and (3) discuss plans for how the glossary can be used by ISEA and updated over time by ISEA and IPCS. The glossary is intended to be a living document that reflects the latest usage and maintains international harmonization of exposure terminology that can be practically applied to improve communication in exposure and related fields.

Adoption of an official ISEA glossary.

A multimedia, multiple pathway risk assessment of atrazine: the impact of age differentiated exposure including joint uncertainty and variability

A multimedia, multiple pathway exposure assessment of atrazine: fate, transport and uncertainty analysis

Publisher Summary
Models provide a means for representing a real system in an understandable way. Conceptual models help to identify the major influences on where a chemical is likely to be found in the environment, and as such, need to be developed to help target sources of data needed to assess an environmental problem. This chapter appraises the available models for predicting exposure to pesticide. In general, developing a model requires two main steps. First, a model of the domain and the processes being studied must be defined. Then, a model of the boundary conditions is especially needed to represent the environment surrounding the study domain. Research scientists often develop physical or dynamic models to estimate the location where a chemical would be expected to move under controlled conditions, only on a much smaller scale. Isolated systems are usually encountered only in highly controlled reactors, so are important in modeling pesticide formulation and manufacturing but are not directly pertinent to pesticide exposure modeling. Pesticide transport and fate models can be statistical (stochastic) and/or deterministic. Statistical models include the pollutant dispersion models, such as the Lagrangian models, which follow the movement of a control volume starting from the source to the receptor locations. Deterministic models are used when the physical, chemical, and other processes are sufficiently understood so as to be incorporated to reflect the movement and fate of chemicals. More comprehensive models provide realistic descriptions of the underlying processes and are invaluable for performing detailed analysis. Thus, the evolution of models will allow for more realistic scenarios, especially regarding personal exposures to pesticides.

Tom McKone

Papers

BETR North America: A regionally segmented multimedia contaminant fate model for North America

Adoption of an official ISEA glossary.

A multimedia, multiple pathway risk assessment of atrazine: the impact of age differentiated exposure including joint uncertainty and variability

A multimedia, multiple pathway exposure assessment of atrazine: fate, transport and uncertainty analysis

Chapter 44 – Modeling and Predicting Pesticide Exposures