Chlordane: thirty-month tumorigenicity and chronic toxicity test in rats.

Groups of 80 Fischer 344 specific-pathogen-free rats of each sex were fed 0, 1, 5, and 25 ppm chlordane for 130 weeks. The rats were examined for hematological, biochemical, urinary, and pathological changes at 26, 52, and 130 weeks of exposure. The original pathologist found statistically significant dose-related changes only in the liver. At 25 ppm chlordane in the diet there were increases in bilirubin levels, liver weight, liver cell volume (centered at the lobules), hepatic necrosis (only in animals found dead or killed in extremis), and hepatocellular nodules (only after 105 weeks of exposure). A peer review of the pathology for all tumors observed on test were spontaneous and unrelated to treatment. From the original pathologist the no-observed-effect level (NOEL) for chlordane in the diet of Fischer 344 rats was found to be 5 ppm. From the peer review data the NOEL in males is 25 ppm and in females is 1 ppm.