Hazard assessments of chemicals in aquatic organisms often include chronic toxicity testing. The evaluation of exposure duration and of the life stages tested according to standard test methods has led to the development of shorter chronic toxicity tests. A similar evaluation of biological endpoints (i.e., survival, growth and reproduction) could result in tests that are more economical. We analyzed endpoints for 28 chemicals and seven fish species in 34 chronic toxicity studies. When all endpoints were compared, survival was equal to or more sensitive than all other endpoints 56 to 69% of the time. Individual endpoints were more sensitive than survival 19 to 61% of the time, except for reproduction, which was always more sensitive (although there were few observations). The no observed effect concentration (NOEC) for growth could be predicted from the NOEC for survival by using interendpoint correlations ( r = 0.949 to 0.974). Ratios of NOECs for survival to those for all other endpoints examined were 5 or less in 93 to 96% of the comparisons (specific endpoint comparisons ranged from 80 to 100%).The determination of the survival endpoint requires less time and money than does the determination of most other endpoints, and it appears adequate for hazard assessments in the initial stage of estimating chronic toxicity. However, a factor of at least 0.2 should be applied to the estimated no-effect concentrations for survival to include other potential biologically significant effects at least 95% of the time. The factor of 0.2 is based on frequency analyses that resulted in the NOECs for survival being 5 times or less than the NOECs for most other endpoints about 95% of the time. Univariate analyses, however, indicated a range of 0.13 to 0.22 for the factor. A thorough evaluation of other published studies that contain endpoints other then survival should be conducted to define the appropriate factor more accurately.

Young rainbow trout Salmo gairdneri (starting age, 17 d) were exposed to nominal concentrations of 0, 0.38, 0.75, 1.5, 3.0, and 6.0 •g/L total polychlorinated biphenyls (PCBs) for 90 d, then held in fresh water for 60 d. Sources of PCBs were (1) waste transformer oil containing various hydrocarbons plus a 1:2 ratio of Aroclors 1254 and 1260, and (2) pure technical PCBs of the same Aroclor ratio as that in the transformer oil. Survival of fish was much lower in transformer oil than in technical PCBs at day 90. Growth was reduced at day 30 by the transformer oil, but not until day 90 at the highest concentration of technical PCBs. Fin erosion was severe and vertebra integrity was reduced in fish exposed to transformer oil but not in fish exposed to technical PCBs. Abnormal swimming behavior of fish exposed to transformer oil was attributed to reduced volume of the swim bladder. Exposures to transformer oil decreased hematocrit, and increased serum cortisol to twice that of controls and of fish exposed to technical PCBs. Exposure to either PCB source increased disease resistance of fish to flush (external) challenges of the bacterium Yersinia ruckeri, but intraperitoneal injection of Y. ruckeri caused faster mortality of fish exposed to transformer oil than of control fish or fish exposed to technical PCBs. All routes of disease exposure should be considered in contaminant-disease interactions. Disease susceptibility or any clinical endpoints measured were never more sensitive indicators of contaminant stress than those endpoints normally examined (growth and survival) in chronic toxicity studies. Because fish took up more PCBs from the technical solutions than from transformer oil, presumably due to petroleum hydrocarbons in transformer oil, environmental assessments of PCBs should include testing the form of the materiaJ that may enter the environment. Polychlorinated biphenyls (PCBs) are among the most ubiquitous and persistent environmental contaminants. An estimated 636,000 t were manufactured in the United States from 1929 to 1977, primarily for use as hydraulic fluids, plasticizers, and dielectric fluids in transformers and capacitors. Despite a steady decrease in production of PCBs after 1971, a 1 O-year survey by the 1 Research for partial fulfillment of Master of Science degree.

Hazard assessments of chemicals in aquatic organisms often include chronic toxicity testing. The evaluation of exposure duration and of the life stages tested according to standard test methods has led to the development of shorter chronic toxicity tests. A similar evaluation of biological endpoints (i.e., survival, growth and reproduction) could result in tests that are more economical. We analyzed endpoints for 28 chemicals and seven fish species in 34 chronic toxicity studies. When all endpoints were compared, survival was equal to or more sensitive than all other endpoints 56 to 69% of the time. Individual endpoints were more sensitive than survival 19 to 61% of the time, except for reproduction, which was always more sensitive (although there were few observations). The no observed effect concentration (NOEC) for growth could be predicted from the NOEC for survival by using interendpoint correlations (r = 0.949 to 0.974). Ratios of NOECs for survival to those for all other endpoints examined were 5 or less in 93 to 96% of the comparisons (specific endpoint comparisons ranged from 80 to 100%). The determination of the survival endpoint requires less time and money than does the determination of most other endpoints, and it appears adequate for hazard assessments in the initial stage of estimating chronic toxicity. However, a factor of at least 0.2 should be applied to the estimated no‐effect concentrations for survival to include other potential biologically significant effects at least 95% of the time. The factor of 0.2 is based on frequency analyses that resulted in the NOECs for survival being 5 times or less than the NOECs for most other endpoints about 95% of the time. Univariate analyses, however, indicated a range of 0.13 to 0.22 for the factor. A thorough evaluation of other published studies that contain endpoints other then survival should be conducted to define the appropriate factor more accurately.