Fathead minnows (Pimephales promelas) were exposed during a partial chronic toxicity test to two DDT concentrations in the water, one in the diet, and combinations of water and diet for 266 days through a reproductive period of their life cycle. Tissue-residue analyses were performed on test fish at preset intervals throughout the exposure and also on embryos, larvae at hatch, and 30- and 60-day progeny. The contribution of DDT from each source was monitored with gas-chromatography and liquid-scintillation techniques. Higher total DDT tissue residues were accumulated from the water than from the diet. Residues contributed by dietary DDT were additive to those from the water. Mean concentration factors were 1.2 times from the diet and 100,000 times from the water. Mortality was higher in fish exposed to DDT in both water and diet than in fish exposed to only one or the other of these sources. DDT in the diet significantly reduced the probability of survival of the test fish (P=0.025). Estimated maximum acceptable toxicant concentrations for DDT are 0.9 micrograms/l for fish exposed to DDT in the water only or 0.4 micrograms/l for fish exposed to DDT in both water and diet.

"Appendix: Recommended bioassay procedure for fathead minnow Pimephales promelas rafinesque chronic tests, by Environmental Research Laboratory-Duluth", 1971, revised 1972 (p. 53-66) Includes bibliographical references (pages 49-52).