Studies were conducted to determine the acute toxicity toxicity of 1,1-dichloroethylene ((vinylidene chloride) VDC) to fish and macroinvertebrates. The methods included a 96-hour static toxicity test using fathead minnow, Pimephales promelas Rafinesque; a 48-hour static toxicity test using water fleas, Daphnia magna Straus; and a 13-day flow-through toxicity test using the fathead minnow, Pimephales promelas Rafinesque. The 96-hour static LC50 value for fathead minnow was 169 (161 to 179)* mg/L. The LC50 value is the calculated concentration of toxicant which would kill 50 percent of the test organisms within a specified time period, e.g., 96 hours. The 48-hour static LC50 for daphnids was 11.6 (9.0 to 14.0) mg/L. The 96-hour flow-through LC50 value for fathead minnows was 108 (85 to 117) mg/L. The threshold LC50 value in flowing water was demonstrated after 7 days to be 29 (23 to 34) mg/L. The threshold LC50 value is achieved when there is no further decline in the LC50 value over a period of three to four days or more. Loss of body equilibrium (swimming disorientation) was the major sublethal toxic effect noted in the static and flow-through fish tests. Many fish affected in the static test recovered in 48 hours, perhaps because of volatilization of the toxicant, However, all affected fish in the flow-through test died by day 7. The 24- and 48-hour LC50 water flea test values were identical, probably because of volatilization of the test material during the first 24 hours. The difference in the static and flow-through fish toxicity values stresses the importance of conducting a flow-through test with volatile chemicals to adequately determine acute and longer term exposure effects (>96 hours).

"July 1980." Includes bibliographical references (page 17).