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Jeff Van Slooten <br /> Page 2 <br /> November 29, 1989 <br /> Meteorological data needs to be obtained, preferably on <br /> site. There is a STAR weather station at Stockton <br /> airport that can provide actual meteorological data for <br /> conditions that should be similar to the site. Since <br /> carcinogens are involved, Industrial Source Complex <br /> Long Term (ISCLT) with annual average concentrations <br /> should be included using the STAR summary data. <br /> Industrial Source Complex Short Term (ISCST) and ISCLT <br /> (when/if done) computer output showing all inputs, <br /> defaults, source coordinate locations and sizes, <br /> receptor locations and model outputs should be <br /> supplied. Worksheets showing all calculations used to <br /> estimate emissions should be supplied. <br /> 2 . Polychlorinated dibenzodioxins (PCDDs) and <br /> polychlorinated dibenzofurans (PCDFs) are common <br /> contaminants of pentachlorophenol (PCP) . Since PCP has <br /> been in use at the site for many years, the dioxin <br /> contamination must be addressed. Although the 2 , 3 , 7 , 8 <br /> tetrachlorodibenzodioxin (TCDD) isomer is not commonly <br /> found in PCP, there is no reason to exclude PCDDs and <br /> PCDFs from the risk assessment. The California DHS has <br /> promulgated a method for estimating the cancer potency <br /> of PCDD and PCDF isomers by conversion of the isomer <br /> concentration to 2 , 3 , 7 , 8 TCDD equivalents <br /> (TEF) (California Air Resources Board, 1986) . There is <br /> evidence that biological receptors, e.g. , fish may <br /> preferentially accumulate certain PCDD and PCDF <br /> isomers, (Goeden and Smith, 1989 and North Atlantic <br /> Treaty Organization, 1988) . Inclusion of PCDDs and <br /> PCDFs, expressed as 2 , 3 , 7 , 8 TCDD equivalents, may <br /> substantially affect the conclusions drawn since <br /> 2 , 3 , 7 , 8 TCDD has a very high cancer potency factor. <br /> 3 . All routes of exposure have not been included in the <br /> assessment of potential risk. Ingestion of soil is one <br /> possible route but dermal absorption, both from <br /> chemicals in soil and from chemicals in the water that <br /> is used for industrial purposes, must also be <br /> considered. Inhalation of both particulates and vapors <br /> must be assessed. <br /> 4 . The risk to biological receptors has not been <br /> adequately evaluated. In PHA, page 1-1, biological <br /> receptors are excluded from consideration without <br /> sufficient rationale. Although the Mormon Slough is <br /> located north of the site, it is not clear that wind <br /> bearing contaminated soil would not deposit on this <br />