翻译谢谢！！！

A chemical that has a median lethal dose (LD50) in air of more than 200 milligrams per kilogram but not more than 2000 ppm by volume of gas or vapor, or more than two milligrams per liter but not more than 20 milligrams per liter of mist, fume, or dust, when administered by continuous inhalation for one hour to albino rats weighing between 200 and 300 grams each.

一种化学物质)的患者平均存活时间是致命剂量(LD50)在空气中超过200毫克每公斤但不超过2000万分之一(体积比)的气体销漏或蒸气或每公升超过2毫克,但不超过20毫克薯镇/升的雾,烟气、或灰尘,当管理为一小时连续吸入白化大数斗粗鼠体重200到300克每个。