The CalTOX multimedia fate and exposure model requires the following specific physical and chemical data: molecular weight, melting point, vapor pressure, Henry's Law constant, aqueous solubility, octanol-water partitioning coefficient, diffusion coefficients in air and water , and reaction half-lives in air, water, soil, and sediment environmental compartments. The model uses all of these parameter values to estimate total human dose associated with a unit release, but it allows some data gaps to be filled using various predictive methods (e.g., CalTOX can estimate parameter x from parameter y).
Some CalTOX parameter values cannot easily be estimated using predictive methods, but are required to generate exposure estimates. Any data gap involving the following parameters (molecular weight, octanol-water partitioning coefficient, melting point, vapor pressure, solubility or diffusion coefficients in air and water) precluded generation of a TEP for a specific chemical. It was not possible to fill these data gaps with default values without introducing substantial uncertainties. Note that this list also includes several chemical categories (such as certain glycol ethers and polycyclic aromatic compounds) that cannot be subjected to fate and exposure modeling because they contain unspecified but very heterogeneous constituents.
To obtain data on physical-chemical properties, CalEPA input datasets were used for 91 chemicals that were included with the CalTOX model. Then the following U.S. EPA databases were used (in preferential order): TRI Indicators, Superfund Chemical Data Matrix, Hazardous Waste Identification Rule, and Waste Minimization Prioritization Tool. When a required value was not found in any of these sources, published values were taken from the following authoritative sources (in preferential order): Mackay (1995), Howard (1989, 1990, 1991, 1993, 1997), Sax (1984), Montgomery (1993, 1996), and other credible sources. Diffusion coefficients not found in these sources were estimated using the SAR methods described in Lyman (1990). If no published half-lives were available for a chemical from reliable sources, the CalTOX default of zero degradation was utilized (effectively assigning such chemicals an infinite half-life).
REFERENCES
EPA, Office of Emergency and Remedial Response. Superfund Chemical Data Matrix(June 1996). OERR, Washington, DC. http://www.epa.gov/superfund/resources/scdm/index.htm
EPA, Office of Pollution Prevention and Toxics.Toxics Release Inventory Relative Risk-Based Environmental Indicators Methodology- Draft(June 1997) and Toxics Release Inventory Relative Risk-Based Environmental Indicators Interim Toxicity Weighting Summary Document(May 1996). OPPT, Washington, DC.
EPA, Office of Solid Waste. Hazardous Waste Identification Rule Technical Support Documents: Risk Assessment for Human and Ecological Receptors. Initial (8/95) and Supplemental (11/95)
Technical Support Documents. OSW, Washington, DC. Obtained as an electronic file.
EPA, Office of Solid Waste and Office of Pollution Prevention and Toxics. Waste Minimization and Prioritization Tool, Beta Test Version 1.0. EPA530-R- 97-019, EPA, Washington, DC.
Hornsby, A.G., R.D. Wauchope, and A.E. Herner. Pesticide Properties in the Environment. Springer-Verlag, N.Y. 1996.
Howard, P.H. Fate and Exposure Data, Volumes 1-5. Lewis Publishers, Chelsea, MI. 1989-1997.
Howard, P.H. Handbook of Environmental Degradation Rates. Lewis Publishers, Chelsea, MI. 1991.
Lyman, W., W. Reehl, and D. Rosenblatt. Handbook of Chemical Property Estimation Methods: Environmental Behavior of Organic Compounds. American Chemical Society, Washington, DC. 1990.
Mackay, D., W. Shiu, and K. Ma. Illustrated Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals, Vol. I-IV. Lewis Publishers, Boca Raton, FL. 1993-1996.
McKone, T. CalTOX, A Multimedia Total Exposure Model for Hazardous Waste Sites. UCRL-CR-111456PtI-IV, Lawrence Livermore National Laboratory, Livermore, CA. 1993.
Montgomery, J.H. Agrochemicals Desk Reference: Environmental Data. Lewis Publishers, Chelsea, MI. 1993.
Montgomery, J.H. Groundwater Chemicals Desk Reference, 2nd Edition. CRC Press, Boca Raton, FL. 1996.
Sax, N.I. Dangerous Properties of Industrial Materials. Van Nostrand Reinhold, New York. 1984.
USDA, Agricultural Research Service. Pesticide Properties Database. http://www.arsusda.gov/rsml/ppdb.html
