Although nitrous oxide is the most commonly administered inhalation anaesthetic, it is not an innocuous agent. Adverse haematologic, neurologic, immune and reproductive effects have been identified in health personnel, among them operating room nurses, anaesthetists and anaesthesiologists. These groups are especially vulnerable to toxicity, owing to trace amounts that may accumulate over a lifetime from occupational exposure. Worldwide, nitrous oxide is commonly used for obstetric analgesia, placing midwives and obstetric nurses among those susceptible to toxicity from excessive and lengthy contact. Despite standards to control hazardous exposure, health personnel cannot become complacent with its use. Below, an examination of current evidence about exposure risks to health personnel and a review of the status of research explaining the genesis of organ-related dysfunction.