AgdaPkt 2016-02-22 Closed and Interview and Joint SA PFA

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APPENDICES City of Redwood City, Public Works Division Initial Study & Mitigated Negative Declaration 10 Blankinship & Associates, Inc. Toxicity Reference Values and Risk For contaminants frequently considered in ecological risk assessments, regulatory agencies, such as USEPA, have developed Toxicity Reference Values (TRVs) for each contaminant. However, published TRVs generally do not exist for pesticides. Therefore, pesticide-specific TRVs were derived as part of this document (USEPA 1999). Endpoints from studies available from the published literature or government reports and databases can be used to establish TRVs. The endpoints used to estimate risk of copper to the longfin smelt were found in the published literature. As applications of copper-containing algaecides and/or aquatic herbicides are sufficiently intermittent, and copper is not significantly persistent within the water column, only acute exposures were considered. As such, acute TRVs are derived for purposes of risk estimation. The USEPA (2004) suggests applying a 20X safety factor to acute median toxicity values (LC50s and LD50s) for aquatic threatened or endangered species when deriving TRVs from literature studies. In this analysis, a safety factor was applied to the endpoint used as a TRV for the longfin smelt. Once a TRV has been derived, it may be compared to an exposure estimate to evaluate whether an adverse effect for a given species is likely to occur. Exposure was estimated assuming the copper containing algaecides and herbicides are applied at the maximum label-allowable rate of 1 mg/L metallic copper, equivalent to 1 part per million (ppm) metallic copper. Risk is estimated by comparing the estimated environmental concentration (EEC) an organism may be exposed to with the derived TRV to calculate a risk. Risk is present when the EEC divided by the TRV is greater than or equal to 1.0. If an estimated exposure is lower than the derived TRV, the resultant risk value is less than 1.0, and the scenario is not considered to pose a risk. Risk = EEC/TRV Where: EEC = Estimated Environmental Concentration TRV = derived Toxicity Reference Value Copper Since no adequate published TRVs for copper were available for saltwater fish species with similar life history to the longfin smelt, the most sensitive and applicable fish endpoint from studies available in the literature was selected. Studies indicate that although early life stages generally are most sensitive, size, rather than developmental stage, may be the more significant factor when evaluating interspecies differences in copper toxicity (Grosell et al., 2007). Thus, similarity in size between the test organism and longfin smelt was an important consideration in the selection of an endpoint for TRV derivation. Additionally, test conditions, such as salinity and duration of exposure, were also considered in the selection process. The USEPA ECOTOX Database was reviewed for appropriate studies (USEPA, 2004). Literature reviewed included numerous saltwater fish acute toxicity studies including Grosell et al. (2007), Burton and Fisher (1990), Krishnani et al. (2003), Mohapatra and Rengarajan (1997), Dung et al. (2005), Torres et al. (1987), and Sappington et al. (2001). Given the breadth of studies available, very few were done with test organisms of similar life stages and size to longfin smelt. The results of Mohapatra and Rengarajan (1997) were selected for derivation of the acute TRV for longfin smelt as the test organisms used (Liza parsia) were of similar size and life stage. This selection approach was taken consistent with the findings of Grosell et al. (2007). See the review below for details on the Mohapatra and Rengararajan (1997) study and endpoint selected for TRV derivation: 6.3.A. - Page 79