| IDENTIFICATION AND USE: Dicyclopentadiene (DCPD) is a colorless crystalline solid (a liquid above 90 degrees F). DCPD is used in the manufacture of cyclopentadiene as a pesticide intermediate; in the production of ferrocene compounds; in paints, varnishes, and resin manufacture; in production of elastomers, resin systems, and polymers. It is also used as a repellent for animals such as hares, rabbits, and deer, in winter or in summer. Applied in the form of impregnated strip on deciduous and coniferous trees, or by spraying around ornamental plants and shrubs. HUMAN EXPOSURE AND TOXICITY: Signs of exposure after inhalation--cough, sore throat, and headache; skin exposure--redness and pain; eyes exposure--redness and pain; Ingestion--abdominal pain, and nausea. Human sensory responses to DCPD were studied in three human volunteers. The odor threshold was reported to be as low as 0.003 ppm. In two of the subjects exposed to 1 and 5.5 ppm for 30 minutes, one subject experienced mild eye and throat irritation after 7 minutes at 1 ppm, and the other subject reported olfactory fatigue after 24 minutes. Eye irritation was reported after 10 minutes, but no olfactory fatigue was reported by either test subject at 5.5 ppm. Accidental exposures of workers, in which headaches were experienced during first 2 months but were not experienced during next 3 months, indicate a certain degree of inurement. ANIMAL STUDIES: In rabbits it was slightly irritating to skin and eyes. Three of four rats survived ten 6-hour daily exposures at 250 ppm, and all survived 15 such exposures at 100 ppm. On daily, repeated exposures to DCPD for 10 days, rats succumbed at the 332 ppm level, but not at the 146 and 72 ppm levels. All dying rats succumbed with convulsions and hemorrhage of the lungs with blood in the intestines; with the females, hemorrhage of the thymus. Mice exposed under the same schedule died at both 146 and 72 ppm. After exposures of 7 hours/day for 89 exposure days, kidney damage was seen in rats exposed at 74 and 35 ppm DCPD. Some lung involvement was seen as chronic pneumonia and bronchiectasis, but no dose related effect was seen in other organs examined. Dogs exposed under the same schedule (89 exposure days) at 32, 23, and 9 ppm DCPD showed only minimal changes in the biochemical tests used, and no changes that were dose-related in 28 organs examined. Hyaline droplets in the proximal convoluted tubular epithelial cells of the kidney were seen in male rats exposed to 5 and 50ppm DCPD and tubular proteinosis was seen by week 13 in all male rats exposed to 50ppm DCPD. Mice were exposed to DCPD by inhalation for 7 hours per day, 5 days per week for 10 days at 47, 72, and 146 ppm. All mice exhibited convulsive deaths on the first day of exposure. Death at 72 ppm occurred in five of six mice of each sex during the 10 days of exposure and was not associated with the convulsions or gross lesions observed in rats. No deaths occurred at 47 ppm and no other effects of treatment were observed. In other study four groups, each consisting of 45 male and 45 female B6C3F1 mice, were exposed to DCPD vapor by inhalation 6 hr/day, 5 days/week, for 13 weeks (64 exposures) at targeted concentrations of 0, 1.0, 5.0, or 50 ppm. Ten male and nine female mice in the highest exposure group died during the study, while no more than two mice died in any other group. 20 female pregnant rats were admin DCPD orally at 0, 80, 250, 750 mg/kg/day for days 6 to 15 gestation. On day 19, the dams were sacrificed and examined; each uterus was examined for implantation sites, placement in uterine horns, number of live and dead fetuses and resorptions. Fetuses were examined for soft tissue changes and skeletal abnormalities. No compound-related gross pathological effects or changes in reproductive performance were seen in the dams. There were no visceral or skeletal malformations or changes in sex ratio in the fetuses. DCPD was not mutagenic in the Salmonella assay at doses of 0, 3, 10, 33, 100, and 333 ug/plate in Salmonella typhimurium strains (TA98, TA100, TA1535, and TA1537) with or without metabolic activation. DCPD did not induce structural chromosomal aberration or polyploidy in CHL/IU cells; negative finding were confirmed in the in vitro micronucleus test. |