Center for Clean Products and Clean Technologies
The University of Tennessee, Knoxville

Introduction
Chemical ranking and scoring (CRS) is a tool for assessing chemicals by considering health, environmental or other hazards, and exposure. CRS either produces a relative ranking of chemicals or assigns chemicals to specific groups or categories. Industry, governmental agencies and academia have developed CRS systems for regulatory or risk management action, priority setting for further investigation and for impact evaluation. Hundreds of CRS systems have been developed in the past twenty years; with little guidance for developing these systems, methods vary widely.

Current and Emerging Uses of CRS. There are many current and potential CRS applications:

• Regulatory and risk management purposes. For example, regulators use CRS to develop lists of chemicals that may threaten state or regional water quality for reporting and monitoring, and for selecting chemicals for bans or phase-outs.

• Priority-setting for further testing.

• To determine pollution prevention priorities. Industry is using CRS to set priorities for research and development, product stewardship activities, and to determine chemical data needs.

• Potentially a very useful tool in the impact assessment stage of Life-Cycle Assessment (LCA), to assess how the inventoried releases might impact human health and the environment.

• Emerging as a tool for waste minimization activities. For example, high priority waste streams can be evaluated to assess the technical and economic feasibility of source reduction and recycling alternatives.

• Governments of many developing countries are facing increased demands for environmental protection; CRS can assist regulators and risk managers to expand existing environmental quality standards and to develop new standards.

SETAC-Sponsored Chemical Ranking and Scoring Workshop

The Society for Environmental Toxicology and Chemistry (SETAC) sponsored a workshop on Chemical Ranking and Scoring, held from February 12 through 17, 1995, in Destin, Florida. Fifty-one experts were brought together from the United States, Austria, Canada, Denmark, Germany, Italy, UK, Switzerland, and South Korea. Participants were from government, industry, academic institutions, and nongovernmental/ environmental organizations. The goal of the workshop was to develop a consensus framework, along with guidelines and principles, for chemical ranking and scoring, in order to promote consistency in the development and application of CRS systems. Five working groups evaluated framework issues, methods for assessing exposure, human health effects, ecological effects and other effects within the context of CRS. Seventeen principles were developed to serve as guidance for those applying an existing CRS system or developing a new CRS system to meet specific goals. Davis et al., (1994a) was a primary piece of background material for this workshop.

Workshop Results. Results of the plenary and workgroup sessions include documenting current and emerging uses of CRS, and the state of the science; identifying key issues in CRS; and developing principles to serve as guidance for those applying an existing CRS system or developing a new CRS system for a specific purpose.

The General Framework. To develop a consensus framework to promote consistency among current and future CRS systems, workshop participants developed guiding principles to improve development and application of CRS. They also identified broad goals of any CRS system; a CRS system should (Davis, 1997):

Organize and transmit information, to transform chemical data into a form that can be presented clearly and consistently to the intended audience. In doing so, a CRS system will facilitate communication between industry, government, academia, environmental advocacy groups, and the public.

Inform management activities, using the available information to differentiate chemicals from each other to show the relative human health, ecological, and/or other impacts of the chemicals. CRS should be used to protect human health and the environment, help guide the development of safer products, and improve the management of the materials in products. A CRS system should communicate uncertainty and increase the understanding of the confidence level of the ranking or scoring and therefore increase the confidence in the decisions about chemicals.

Principles. The following principles apply to the development of any CRS system, or for the selection of an existing system for a particular application. In developing these principles it was recognized that CRS used for different applications may have different forms and levels of complexity. Regardless of the application, however, a CRS system should:

• Have a clearly defined purpose.
• Include both effects and exposure data, as is consistent with the risk assessment paradigm.
• Acknowledge and assess uncertainty.
• Acknowledge the role of professional judgment.
• Consider effects relevant to the goals.
• Recognize the role of valuation in aggregation and weighting of different endpoints.
• Have transparent methods and outputs.
• Be neutral to data availability, unless it is consistent with the intended use to have a positive or negative bias.
• Accommodate extreme data variability across chemicals.
• Use a tiered approach.
• Assess similar effects/exposure categories consistently across tiers.
• Preserve critical information.
• Specify data selection guidelines.
• Be theory driven as well as data driven.
• Include sensitivity analysis.
• Be consistent with any preselection of chemicals.
• Consider the impacts of scaling.

(From Davis, 1997)

Chemical Hazard Evaluation for Management Strategies (CHEMS)

A chemical ranking and scoring method entitled Chemical Hazard Evaluation for Management Strategies (CHEMS-1), was developed as a screening tool to provide a relative assessment of chemical hazards to human health and the environment.

• Purpose: to place chemical release data into perspective by evaluating both the toxic effects of chemicals and the potential exposure to those chemicals.

• Approach: combining measures of chemical toxicity pertaining to both human health and the environment with chemical release amounts and information on environmental persistence and bio-accumulation.

• CHEMS-1 was developed as a screening-level assessment tool, for use in a tiered approach.

• Designed for flexibility, transparency.

CHEMS was initially developed for assessing safer substitutes for major product and process uses, where chemicals were selected from Toxics Release Inventory (TRI) and annual pesticide usage data (See Swanson et al., 1997 and Davis et al., 1994b).

Hazard values are determined for human health effects, ecotoxic effects, persistence, and bio- accumulation. Hazard values can be used alone or combined with use and/or release amounts.

Human Health Effects. Hazard values are determined for acute and chronic human health effects based on available toxicity data.

man health effects

• acute oral toxicity: rodent oral LD50
• acute inhalation toxicity: rodent inhalation LC50

Chronic human health effects

• carcinogenicity: evidence of carcinogenicity, EPA and International Agency for Research on Cancer (IARC) classifications.
• chronic, non-cancer toxicity: 'other specific effects', positive evidence of mutagenicity, developmental effects, reproductive effects, other chronic effects, and neurotoxicity.

For chronic, non-cancer toxicity, the evidence of effect scoring has been replaced with the use of NOAELs and LOAELs.

Environmental Effects. Hazard values are determined for acute terrestrial and aquatic effects and chronic fish toxicity based on available data and quantitative structure-activity relationships (QSARs).

Terrestrial, acute effects

• acute oral toxicity, rodent oral LD50

Aquatic, acute effects

• acute toxicity to fish, fish LC50

Aquatic, chronic effects

• chronic toxicity to fish, fish NOEL

Exposure potential. Hazard values are determined for environmental persistence and potential to bioaccumulate based on measured data, QSARs and/or professional judgement. Amount used or released can also be taken into account.

Persistence

• Biological oxygen demand (BOD) half-life
• Hydrolysis half-life
• Bioconcentration factor

Amount used/released

• Release weighting factor (RWF), determined by the amount of annual releases or transfers, is used to weight chemical toxicity hazard values.

The Algorithm. A total hazard value is calculated for a chemical based on its toxicity, persistence, and potential bio-accumulation in the environment. The basic algorithm is:

Total hazard value = (Human Health Effects + Environmental Effects) * Exposure Factor

Human Health Effects = aHV_OR + bHV_INH + cHV_CAR + dHV_NC

HV_OR = hazard value for acute oral toxicity (0-5)
HV_MH = hazard value for acute inhalation toxicity (0-5)
HV_CAR = hazard value for carcinogenicity (0-5)
HV_NC = hazard value for chronic, noncancer toxicity (0-5)

Environmental Effects = eHV_MAM +fHV_FA+ gHV_FC

HV_MAM = hazard value for acute oral toxicity (other mammalian) (0-5)
HV_FA = hawd value for acute toxicity to fish (0-5)
HV_FC = hazard value for chronic toxicity to fish (0-5)

Exposure Factor = hHV_BOD + iHV_HYD + jHV_BCF

HV_BOD = hazard value for biodegradation (1-2.5)
HV_HYD = hazard value for hydrolysis degradation (1-2.5)
HV_BCF = hazard value for aquatic bioconcentration (1-2.5)

a..j = term weighting factors (i.e., importance weights, based on the decision-maker’s values)

Release-weighted HV = total hazard value * RWF
      RWF = ln[releases (tons)] +x where x depends on the range of release amounts ( > 0)

Modified CHEMS for Relative Impact Assessment. CHEMS is being modified for use in life- cycle impact assessment, as part of the development of a life-cycle design tool. The general form of the impact score (IS) equations is:

IS = HV x LCI x Fate

where:

HV = specific hazard value(s) for an impact type (e.g., acute human health effects)
LCI = amount of chemical or material release from the life-cycle inventory (LCI) (in lbs or kg per functional unit)
Fate = factor accounting for multimedia partitioning and degradation

More information on this methodology is available upon request.

REFERENCES

Davis, G.A. 1997. "Framework for Chemical Ranking and Scoring Systems." In: Chemical Ranking and Scoring.- Guidelines for Relative Assessments of Chemicals. M. B. Swanson and A. C. Socha, eds. SETAC Press, Pensacola, FL.*

Davis, G. A., M. B. Swanson, and S. L. Jones, 1994a. Comparative Evaluation of Chemical Ranking and Scoring Methodologies, University of Tennessee, Center for Clean Products and Clean Technologies, Knoxville, TN. For the U.S. EPA Office of Pollution Prevention and Toxics, Washington, DC.**

Davis, G. A., L. Kincaid, M. B. Swanson, T. Schultz, J. Bartmess, B. Griffith, & S. Jones, 1994b. Chemical Hazard Evaluation for Management Strategies: A Method for Ranking and Scoring Chemicals by Potential Human Health and Environmental Impacts. The University of Tennessee, Center for Clean Products and Clean Technologies, U.S. EPA Risk Reduction Engineering Laboratory Office of Research and Development, Cincinnati, OH. EPA/600/R- 94/177.**

M. B. Swanson and A. C. Socha, eds. 1997. Chemical Ranking and Scoring.- Guidelines for Relative Assessments of Chemicals. SETAC Press, Pensacola, FL.*

M. B. Swanson, G. A. Davis, L.E. Kincaid, T. Schultz, J. Bartmess, S. Jones and E.L. George. 1997. "A Screening Method for Ranking and Scoring Chemicals by Potential Human Health and Environmental Impacts. " Environmental Toxicology and Chemistry, 16, 3 72-3 8 3. *

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*available from SETAC (http://www.setac.org/)

** Available from the Center for Clean Products and Clean Technologies
The University of Tennessee, Knoxville
311 Conference Center Building
Knoxville, TN 37996

Address:
The University of Tennessee
Center for Clean Products and
Clean Technologies
Energy, Environment and Resource Center
600 Henley Street
Suite 311
Knoxville, TN 37996-4134

Phone: (423) 974-0642
Fax: (423) 974-1838
E-Mail: MSWANSO1@UTK.EDU

Mary Swanson is a project scientist with the University of Tennessee's Energy, Environment and Resources Center and the Center for Clean Products and Clean Technologies. Her work involves evaluating the fate and effects of chemicals released to the environment, with special interest in the development and application of chemical ranking and scoring, risk assessment, and life-cycle impact assessment methodologies as tools for evaluating and developing cleaner products and cleaner technologies.

Ms. Swanson has twelve years experience in environmental research and consulting, beginning with research at the University of Minnesota involving trace organic contaminants in rain and snow in the Great Lakes region. She also worked in environmental consulting as an environmental chemist/environmental engineer on hazardous waste site remedial investigations and feasibility studies, specializing in the areas of contaminant fate and transport modeling and human health risk assessment.

Ms. Swanson received a Master of Science degree in environmental engineering from the University of Minnesota in 1988 and a Bachelor of Science degree in natural resources/water chemistry from the University of Wisconsin-Stevens Point in 1984.