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SAFEWAY MEAT PACKING FACILITY, STOCKTON, CALIFORNIA <br /> TIER H RISK ]BASED CORRECTIVE ACTION <br /> FEBRUARY 26, 1996 <br /> PAGE 2 - 2 <br /> have developed SFs for benzene, STTLs using SFs from both organizations have been developed <br /> for the Stockton site Table 3 provides the SFs used in this assessment <br /> All of the COIs have potential noncaremogemc health effects The USEPA (1995b) reference <br /> doses (RfDs) have been used to characterize the potential noncarcmogenic health threats <br /> Noncarcinogeruc chemicals are believed to have threshold concentrations health effects are not <br /> believed to occur at doses below certain levels Based on the threshold concept, USEPA has <br /> established RfD to characterize the minimum exposure which is likely to cause noncarcinogenic <br /> health effects The unit of an RfDs is "mg/kg-day " The ratio of the average daily dose of a <br /> chemical (in mg/kg-day) to FM is the hazard quotient or HQ hf the HQ is less than 1 the <br /> concentration of the chemical in the environment will not result in an individual being exposed <br /> above the threshold dose Noncarcinogeruc health effects are not expected to occur Table 3 <br /> provides the RfDs used in this assessment <br /> USEPA does not have an RfD for either 1,2,4-tnmethylbenzene or phenanthracene For this <br /> RSCA evaluation, RfDs for these compounds have been selected from related chemicals The <br /> surrogate chemicals were based on structure-activity relationships to the C01s <br /> • The RfDs for xylene has been used to characterize the - <br /> � toxicity of 1,2,4 <br /> trimethylbenzene based on the close structural relationship between the two <br /> chemicals Xylene has two methyl groups attached to a benzene ring and 1,2,4- <br /> trunethylbenzene has three methyl groups They both cause central nervous <br /> system effects and they have similar acute toxicities (Sax and Lewis, 1989) <br /> • The RfDs for anthracene have been used to characterize the toxicity phenanthrene <br /> Both compounds are planer (or flat) polycyclic aromatic hydrocarbons composed <br /> of three benzene rings anthracene is a straight chain of linked benzene rings and <br /> phenanthrene is a branched chain <br /> cDsi <br />