Yagiela J A
Section of Oral Biology, School of Dentistry, University of California, Los Angeles.
Anesth Prog. 1991 Jan-Feb;38(1):1-11.
Recent adoption by the American Conference of Governmental Industrial Hygienists of a Threshold Limit Value of 50 ppm for an 8-hour average exposure to nitrous oxide (N2O) increases the likelihood for its regulation by state and federal occupational health agencies. This review outlines current information on the health risks of N2O inhalation to provide a basis from which safe and reasonably attainable exposure limits can be proposed. Although N2O was for many years believed to have no toxicity other than that associated with its anesthetic action, bone marrow depression in patients administered N2O for extended periods of time and neurological abnormalities in health care workers who inhaled N2O recreationally have disproved this notion. Retrospective surveys of dental and medical personnel have also linked occupational exposure to N2O with a number of health problems and reproductive derangements. Nitrous oxide reacts with the reduced form of vitamin B12, thereby inhibiting the action of methionine synthase, an enzyme that indirectly supports methylation reactions and nucleic acid synthesis. Many, if not all, of the nonanesthetic-related adverse effects of N2O may be ascribed to this action. Animal and human studies indicate that the toxic effects of N2O are concentration- and time-dependent. It is suggested that a time-weighted average of 100 ppm for an 8-hour workday and/or a time-weighted average of 400 ppm per anesthetic administration would provide adequate protection of dental personnel and be achievable with existing pollution control methods.
美国政府工业卫生学家会议最近采用了一氧化二氮（N₂O）8小时平均暴露阈限值为50 ppm，这增加了州和联邦职业健康机构对其进行监管的可能性。本综述概述了当前关于吸入N₂O健康风险的信息，以便为提出安全且合理可行的暴露限值提供依据。尽管多年来人们认为N₂O除了与麻醉作用相关的毒性外没有其他毒性，但长期接受N₂O治疗的患者出现骨髓抑制以及娱乐性吸入N₂O的医护人员出现神经异常，证明了这种观念是错误的。对牙科和医疗人员的回顾性调查也将职业性接触N₂O与许多健康问题和生殖紊乱联系起来。一氧化二氮与还原型维生素B₁₂反应，从而抑制蛋氨酸合成酶的作用，该酶间接支持甲基化反应和核酸合成。N₂O的许多（如果不是全部）与麻醉无关的不良反应可能归因于这一作用。动物和人体研究表明，N₂O的毒性作用与浓度和时间有关。建议8小时工作日的时间加权平均浓度为100 ppm和/或每次麻醉给药的时间加权平均浓度为400 ppm，这将为牙科人员提供充分保护，并且通过现有的污染控制方法可以实现。
