Continuous Animal Exposure to Methylene-Chloride,
AEROSPACE MEDICAL RESEARCH LAB WRIGHT-PATTERSON AFB OHIO
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Dichloromethane, also known as methylene chloride, is used extensively as a solvent in many of the space cabin construction materials. The provisional space cabin limit has been set at 25 ppm for 90-day flights, and 5 ppm for 1000-day flights. To properly assess the inhalation hazard to astronauts, 2 high levels, 1000 and 5000 ppm, were intentionally selected and 4 animal species were exposed continuously to these concentrations for periods of not more than 14 weeks. The following observed changes were most significant 1 Severe weight losses were observed in all species, most profound in dogs. 2 Dogs and monkeys continued to lose weight throughout the exposure or until death, and rats showed dose related subnormal growth rates when compared with controls. 3 At 5000 ppm dichloromethane, there were considerable deaths during the first 3 weeks 50 in dogs, 25 in monkeys and 35 in mice. No rats died. At 1000 ppm exposure level, significant deaths occurred only in dogs when 6 died during the 6th and 7th weeks and the remaining 2 dogs became moribund. 4 Monkeys exposed to dichloromethane at 1000 ppm level for 14 weeks showed clinical signs of liver injury. 5 Rats showed no response at either exposure level other than growth depression. 6 Dogs that died exhibited gross lesions associated with hepatic failure.