Male cynomolgus monkeys were exposed to 0 (control), 50, or 100 ppm ethylene oxide (ETO) for 7 hrs/day, 5 days/wk for 24 months. Ophthalmic examinations were performed during the 24th month of exposure and on surviving animals following 10 years with no additional ETO exposures. Following sedation with IM ketamine/xylazine, mydriasis was induced with topical 1% tropicamide hydrochloride. Eyes were examined by a board certified veterinary ophthalmologist using a hand-held slit lamp and ophthalmoscope. At the first exam, the incidences of lens opacities were: controls 0/12, ETO 50 ppm 2/11 (3 opacities), and ETO 100 ppm 3/11 (6 opacities). At the second exam, the incidences were: controls 2/4 (3 opacities), ETO 50 ppm 2/3 (4 opacities), and ETO 100 ppm 4/4 (8 opacities). Overall, the combined incidences were: controls (2/12; 3 opacities), ETO 50 ppm (4/11; 7 opacities), and ETO 100 ppm (6/11; 12 opacities). No significant differences in the incidence of opacities were observed at either time point or with the combined data using Chi-square. The opacities observed at the second exam varied over a wide range and were graded as minimal/subtle (grade 1) to severe (grade 5). A repeated measures design was used to compare the severity of lens lesions in the 11 control and exposed monkeys, and the effect of dose was significant (F (2,8) = 8.88, P = .0093). Fisher's LSD test showed that the ETO 100 ppm group (mean lens severity rating 3.63) was significantly different (p <0.05) from the controls (mean lens severity 0.38). The finding of opacities in monkeys exposed to ETO is consistent with reports of cataracts in sterilizer operators occupationally exposed to high levels of ETO.
The Toxicologist. Society of Toxicology 31st Annual Meeting, February 23-27,1992, Seattle, Washingtion