This letter is to inform you of the preliminary results of a 28-day feeding study with 6-weeks of recovery in rats with the above referenced test substance. Groups of 100 male and 100 female rats were fed diets containing concentrations of 0, 10, 30, 300, or 3000 ppm of the test substance. After 14 days of dietary administration, the 3000 ppm treatment group was euthanized without pathology due to excessive body weight loss. At three timepoints during the dietary administration of the test substance, samples were collected for analyses: 1-week, 2-week, 4-week. In addition, various samples were collected for analyses from three recovery timepoints after the cessation of treatment: 2-week recovery, 4-week recovery, 6-week recovery. Analyses that were performed included liver and thyroid gland weights, thyroid hormone concentrations serum thyroxine (T4), triiodothyronine (T3), reverse Tz (rT3), and thyroid-stimulating hormone (TSH), serum iodide (T) concentrations, hepatic enzyme activity (S'-deiodinase and UDP-glucurony1transferase (UDPGT)), hepatic and thyroid follicular cell proliferation, and hepatic and thyroid gland histopathology. At 10 ppm, a statistically significant decrease in serum T4 concentrations was observed at the 1-week timepoint. In addition, a statistically significant decrease in serum T3 concentrations was observed at the 4-week recovery timepoint. No changes in organ weights, serum T, cell proliferation, or histopathology were observed at any timepoint.