SummaryA relationship between polybrominated biphenyl, Firemaster FF-1 (FF-1), in the diet, and eggs, as monitored by hexahromobiphenyl (6-BB), and embryo toxicity, as measured by hatchability, were examined. The minimum dietary level of FF-1 for an effect on hatchability was estimated at 42 ppm, which produced an egg residue estimated at 65.9 ppm 6-BB. Generally, as FF-1 in the diet increased, egg residues increased and hatchability decreased. Regression equations were established for these relationships. After withdrawal of FF-1 in the diet, hatchability returned to normal when FF-1 treatments had been <625 ppm. Over a range of 30-85 ppm 6-BB in eggs there was poor correlation to an effect on hatchability. These latter data were discussed in terms that the 6-BB peak may not be a definitive approach to assess FF-1 toxicity.The authors express their appreciation for assistance in this project to Mr. Sulo Hulkonen, Mr. Edward Kowaleski, Mr. Dennis Dodson, and Ms. Melinda Neff.