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<p>Nitrous oxide (N<sub>2</sub>O) is classified as a reproductive toxicant (Repr. 1B, H360D) under the EU CLP Regulation based on developmental toxicity findings in non-guideline rat studies conducted in the 1970s and 1980s. Those studies reported malformations and embryolethality after continuous 24-h exposures to high and anesthetic concentrations of N2O, but provided limited data on maternal toxicity and may have been confounded by hypoxia. A new prenatal developmental toxicity study was conducted in Wistar rats according to OECD Test Guideline 414 and following Good Laboratory Practice (GLP). Mated females (21–24 per group) were exposed nose-only to target concentrations of 0 (air control), 150,000; 380,000; or 750,000&#xa0;ppm N<sub>2</sub>O for 6&#xa0;h/day from gestation day (GD) 6 to GD 19. All test atmospheres contained ≥ 25% oxygen and blood oxygen saturation was monitored to preclude hypoxia. No maternal mortality or clinical signs were observed. Body weight gain in dams was reduced at 750,000&#xa0;ppm (− 15%); however, terminal body weights and gravid uterus-corrected body weight gains remained comparable to controls. Reproductive parameters were unaffected. No treatment-related malformations were detected at external, visceral or skeletal examinations in any group. Fetal body weight was reduced (− 8%) and the incidence of unossified sternebrae, a skeletal variation, increased only at the high dose, consistent with maternal toxicity and growth retardation. These results show that N<sub>2</sub>O does not induce selective developmental toxicity in rats when tested under current OECD guideline conditions.</p>

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Prenatal developmental toxicity of nitrous oxide: results of a GLP-compliant OECD TG 414 study in rats and implications for hazard classification

  • 期刊论文

  • 发表日期：

    2026年6月27日

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  • Thomas Colnot,
  • Wolfgang Dekant

摘要

Nitrous oxide (N2O) is classified as a reproductive toxicant (Repr. 1B, H360D) under the EU CLP Regulation based on developmental toxicity findings in non-guideline rat studies conducted in the 1970s and 1980s. Those studies reported malformations and embryolethality after continuous 24-h exposures to high and anesthetic concentrations of N2O, but provided limited data on maternal toxicity and may have been confounded by hypoxia. A new prenatal developmental toxicity study was conducted in Wistar rats according to OECD Test Guideline 414 and following Good Laboratory Practice (GLP). Mated females (21–24 per group) were exposed nose-only to target concentrations of 0 (air control), 150,000; 380,000; or 750,000 ppm N2O for 6 h/day from gestation day (GD) 6 to GD 19. All test atmospheres contained ≥ 25% oxygen and blood oxygen saturation was monitored to preclude hypoxia. No maternal mortality or clinical signs were observed. Body weight gain in dams was reduced at 750,000 ppm (− 15%); however, terminal body weights and gravid uterus-corrected body weight gains remained comparable to controls. Reproductive parameters were unaffected. No treatment-related malformations were detected at external, visceral or skeletal examinations in any group. Fetal body weight was reduced (− 8%) and the incidence of unossified sternebrae, a skeletal variation, increased only at the high dose, consistent with maternal toxicity and growth retardation. These results show that N2O does not induce selective developmental toxicity in rats when tested under current OECD guideline conditions.