CHRONIC TESTS 



Except for chronic toxicity tests with fathead minnows ( Pimephales 

 promelas ), chronic or partial chronic tests with various aquatic forms-- 

 sheepshead minnows ( Cyprinodon variegatus ), brook trout ( Salvelinus 

 fontinalis ), bluegi lis, daphnids, and midges--are considered tentative or 

 developmental. Because such studies may be required to appraise the hazard 

 of a pesticide to non-target animals, I would like to summarize the results 

 of two studies that we (Staff, Fish-Pesticide Research Laboratory) recently 

 conducted one with toxaphene (Mayer, Mehrle, and Dwyer, in press; Mehrle 

 and Mayer, in press) and one with 3-trif luoromethyl-4-nitrophenol (TFM) 

 (Foster Mayer, personal communication). 



Toxaphene Investigations 



Growth and reproductive effects —Although use organochlorine insecti- 

 cides has been reduced in recent years, some including toxaphene are still 

 used extensively. Between 30 and 40 million pounds of toxaphene are 

 currently being applied annually on crops and livestock in the United 

 States. Since use of DDT was curtailed, toxaphene has often been used to 

 replace it, alone or in combination with other insecticides. We therefore 

 began cooperative studies in 1972 with EPA to evaluate the effects of toxa- 

 phene on fishery resources. 



Toxaphene is acutely toxic to fish; lethal threshold concentrations for 

 brook trout, bluegi lis, fathead minnows, and channel catfish range from 0.5 

 to 15.2 yg/liter. In earlier studies we found that growth of adult brook 

 trout was reduced during continuous exposure to 0.29 and 0.50 yg/liter toxa- 

 phene, and the added stress of natural spawning caused extensive deaths of 

 adults at these concentrations. Growth and survival of fry were affected 

 adversely at concentrations as low as 0.039 yg/liter, and they accumulated 

 toxaphene residues 5,000 - 21,000 times the water concentration. 



Because toxaphene is used extensively on cotton in the southeastern 

 United States, we also tested it against the fathead minnow, an important 

 forage and bait species, and against channel catfish. Ten-day-old fathead 

 minnow fry were exposed continuously to concentrations of 0.06 - 1.2 

 yg/liter of toxaphene. The fish were reared at a constant temperature of 

 24 C and under a regulated photoperiod approaching natural lighting. 

 Growth of the fish was not affected in exposures as long as 90 days. 

 Between 90 and 150 days, however, the growth of all fish exposed to toxa- 

 phene was significantly less (P<0.05) than that of the control fish. At 

 this time toxaphene residues accumulated during this period exceeded 90,000 

 times those in the treated water. Residues in fish exposed to the highest 

 concentration, 1.2 yg/liter, averaged 94 yg/g. 



Two-year-old channel catfish were also exposed continuously to concen- 

 trations of 0.023 - 0.51 yg/liter of toxaphene for 4.5 months before 

 spawning (Figure 2). Spawning occurred naturally through manipulation of 

 photoperiod and water temperature, and 85% of the fish that reached sexual 

 maturity spawned. Although the adults were not affected, hatchability of 



172 



