A variety of landscape characteristics influence the environmental fate of chemicals. To predict the environmental concentrations that result from chemical releases to air or water, CalTOX requires several types of
landscape data including meteorological data (precipitation, average annual wind speed, deposition velocities, air temperature, and depth of the mixing layer), hydrological data (annual rainfall, runoff, soil infiltration, ground-water recharge, surface water depth and sediment loads), and soil properties (bulk density, porosity, water content, and root-zone depth).
As input to CalTOX, a US landscape data set was constructed by calculating area-weighted mean regional values. Regional landscape parameters were obtained as area-weighted averages of state-level data. Individual data elements were garnered from several sources, including the U.S. Statistical Abstract (U.S. Bureau of Census, 1997) and The Water Encyclopedia (Van Der Leeden, et al., 1990).
Scorecard utilizes CalTOX to generate TEPs that are applied to reported environmental releases, based on the assumption that averaged landscape parameters are an acceptable default for predicting environmental fate anywhere in the U.S. or Canada. Uncertainty and sensitivity analyses have shown that CalTOX calculations are much less sensitive to landscape properties than to chemical properties (Maddalenda et al., 1995). In addition, analyses have been conducted by scientists at the School of Public Health, University of California at Berkeley and at the U.S. EPA to investigate whether chemical-specific TEPs would differ significantly if their exposure component was modeled using landscape parameters from different North American regions. These studies have demonstrated that there is very little inter-regional variation in chemical-specific TEPs due to differences in landscape parameters (McKone, et al., 1998).
REFERENCES
CalEPA, Department of Toxic Substances Control. Guidance for Site Characterization and Multimedia Risk Assessment for Hazardous Substances Release Sites, Volume 2. Chapter 2: Documentation of Assumptions Used in the Decision to Include and Exclude Exposure Pathways. A report prepared for the State of California, Department of Toxic Substances Control, Lawrence Livermore National Laboratory, UCRL-CR-103462. Livermore, CA.
CalEPA, Department of Toxic Substances Control. Guidance for Site Characterization and Multimedia Risk Assessment for Hazardous Substances Release Sites, Volume 2. Chapter 3: Guidelines for the Documentation of Methodologies, Justification, Input, Assumptions, Limitations, and Output for Exposure Models. A report prepared for the State of California, Department of Toxic Substances Control, by Lawrence Livermore National Laboratory, UCRL-CR-103460. Livermore, CA.
Hertwich, E.G. Toxic Equivalency: Addressing Human Health Effects in Life Cycle Impact Assessment. A dissertation submitted for the degree of Doctor of Philosophy in Energy and Resources in the Graduate Division of the University of California, Berkeley. Spring 1999.
Hertwich, E.G.; T. McKone; W. Pease. Parameter uncertainty and variability in evaluative fate and exposure models. Risk Analysis 19(6):1193-1204. 1999.
Layton, D.W.; T.E. McKone; C.H. Hall; M.A. Nelson; Y.E.Ricker. Demilitirazation of Conventional Ordnance: Priorities for Data-Base Assessments of Environmental Contaminants. A report prepared for U.S. Army Medical Research and Development Command, Fort Detrick, Frederick, MD, by Lawrence Livermore Nation Laboratory, UCRL-15902. Livermore, CA.
Maddalena, R.L.; McKone, T.E.; Layton, D.W.; Hsieh, D.P.H. Comparison of multi-media transport and transformation models - Regional fugacity model vs CalTOX. Chemosphere 30: 869-899. 1995.
McKone, T.E.; A. Bodnar; E.G. Hertwich. Development and Evaluation of
State-Specific Landscape Data Sets for Life-Cycle Analysis. A report prepared
by the University of California Berkeley, for the U.S. Environmental Protection Agency Sustainable Technology Division, National Risk Management Research Laboratory, Cincinnati (August 1998 Draft).
National Oceanic and Atmospheric Administration. National Climatic Data Center. http://www.ncdc.noaa.gov/
Pankow, J.F., et al. The Urban Atmosphere as a Non-Point Source for the Transport of MTBE and Other Volatile Organic Compounds (VOCs) to Shallow Groundwater. Environmental Science & Technology 31(10): 2821-8. 1997.
Saxton, K.E., at al. Estimating generalized soil-water characteristics from texture. Soil Science Society of America Journal 50(4): 1031-6. 1986.
U.S. Bureau of Census. 1997 U.S. Statistical Abstract. http://www.census.gov/ftp/pub/mp/www/pub/gen/msgen11d.html
U.S. EPA. Pesticide Assessment Tool for Rating Investigations of Transport (PATRIOT), v. 1.20, November 1994.
Van Der Leeden, F.; Troise, F.L.; Todd, D.K. The Water Encyclopedia, 2nd Edition. Lewis Publishers, Chelsea, MI. 1990.
