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The toxicity of octamethylcyclotetrasiloxane (OMCTS) to representative freshwater and marine fish and invertebrates was investigated. Testing procedures followed Toxic Substance Control Act (TSCA) guidelines with chemical‐specific adaptations as presented in the OMCTS Testing Consent Order (Docket OPTS‐42071A). The physicochemical properties and behavior of OMCTS (i.e., high volatility, low water solubility) precluded the use of conventional experimental practices and exposure systems. Procedures and systems developed during these investigations provided a mechanism that produced exposure levels equal to the maximum achievable (i.e., “functional”) solubility of OMCTS in natural dilution waters. The toxicant delivery systems and exposure chambers were designed to minimize volatilization by elimination of the air/water interface. The flow‐through systems maintained consistent exposure concentrations and adhered to U.S. Environmental Protection Agency (EPA) Guideline test performance criteria. The “functional” water solubility of OMCTS in freshwater and seawater ranged from 14 to 30 μg/L and from 6.0 to 9.0 μg/L, respectively. Functional water solubility appeared to vary slightly with test conditions and dilution water characteristics. Continuous exposures of 2 to 93 d were conducted during these investigations with daphnids (Daphnia magna), rainbow trout (Oncorhynchus mykiss), mysids (Mysidopsis bahia), and sheepshead minnow (Cyprinodon variegatus). The rainbow trout was determined to be the most sensitive species to OMCTS (14‐d LC50 = 10 μg/L). At levels equal to the functional water solubility, OMCTS was not acutely toxic to D. magna, mysids, or sheepshead minnow. The survival of D. magna was reduced by 16%, relative to the control organisms, after 21‐d exposures to 15 μg/L OMCTS; exposure to 7.9 μg/L OMCTS or less had no effect on daphnid survival or reproduction. No toxicity was observed at the highest concentration tested in a 93‐d exposure of rainbow trout early life stages. The no‐observed‐effect concentration for this study was 4.4 μg/L, the same as determined in a 14‐d extended acute study.

The toxicity of octamethylcyclotetrailoxane (OMCTS) to representative freshwater and marine fish and invertebrates was investigated. Testing procedures followed Toxic Substance Control Act (TSCA) guidelines with chemical-specific adaptations as presented in the OMCTS Testing Consent Order (Docket OPTS-42071A). The physicochemical properties and behavior of OMCTS (i.e., high volatility, low water solubility) precluded the use of conventional experimental practices and exposure systems. Procedures and systems developed during these investigations provided a mechanism that produced exposure levels equal to the maximum achievable (i.e., "functional") solubility of OMCTS in natural dilution waters. The toxicant delivery systems and exposure chambers were designed to minimize volatilization by elimination of the air/water interface. The flow-through systems maintained consistent exposure concentrations and adhered to U.S. Environmental Protection Agency (EPA) Guideline test performance criteria. The "functional" water solubility of OMCTS in freshwater and seawater ranged from 14 to 30 pg/L and from 6.0 to 9.0 pg/L, respectively. Functional water solubility appeared to vary slightly with test conditions and dilution water characteristics. Continuous exposures of 2 to 93 d were conducted during these investigations with daphnids (Daphnia magna), rainbow trout (Oncorhynchus mykiss), mysids (Mysidopsis bahia), and sheepshead minnow (Cyprinodon variegatus). The rainbow trout was determined to be the most sensitive species to OMCTS (14-d LC50 = 10 pg/L). At levels equal to the functional water solubility, OMCTS was not acutely toxic to D. magna, mysids, or sheepshead minnow. The survival of D. magna was reduced by l6%, relative to the control organisms, after 21-d exposures to 15 pg/L OMCTS; exposure to 7.9 pg/L OMCTS or less had no effect on daphnid survival or reproduction. No toxicity was observed at the highest concentration tested in a 93-d exposure of rainbow trout early life stages. The no-observed-effect concentration for this study was 4.4 pg/L, the same as determined in a 14-d extended acute study.

Evaluation of the possible impacts of rodenticides on wildlife must be conducted in the context of riskbenefit considerations. Harmful introduced pests (e.g ., commensal rats and mice) historically have required management around human habitation for economic and public health reasons. Disparate views of limited data have accumulated concerning the wildlife impacts resulting from commensal rodent control activities. The founding of the Rodenticide Registrants Task Force (RRTF). a trade association that includes all the major manufacturers and importers of anticoagulant rodenticide products (and bromethalin, a non-anticoagulant rodenticide) in the U.S., is described. The potential for anticoagulant dispersion in wildlife via primary and secondary routes is considered. Toxicology and pharmacokinetic studies are analyzed to obtain a better understanding of the biological and toxicological significance of low levels of rodenticide in animal tissue. A framework to address rodenticide impact to wildlife is presented. It is based upon the example of long-tenn cooperative efforts in England involving government, environmental, and manufacturer groups.

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