甲基叔丁基醚（MTBE）是用于非美国地理位置的燃料增氧剂。多次健康评论得出结论，MTBE不是人类相关致癌物质，并提供了更新的作用机制（MOA）、接触、剂量和风险视角，支持这些结论。MTBE是非基因毒性的，并且血液浓度方面具有很大的暴露边际，整体大鼠400 ppm吸入NOAEL的血浓度和典型工作场所或一般人口暴露的血浓度之间的间隔很大。非癌症和阈值癌症危险性商数从燃料泵汽油站工作人员的0.046到一般人口暴露的100-1,000倍较低。对于假定这些同样情况的基因毒性的癌症风险，保守的估算都小于1×10-6。大鼠吸入暴露低于3000 ppm时MTBE非线性毒动力学（TK）出现，而这个剂量在燃料使用情境下也不实际可行，表明高剂量特异性的雄性大鼠肾脏和睾丸（3000和8000 ppm）以及雌性小鼠肝脏肿瘤（8000 ppm）对人类来说不具数量上的相关性。作用机制分析也表明MTBE雄性大鼠肾脏肿瘤，以及较小程度的女性小鼠肝脏肿瘤对人类来说没有定性相关性。因此，毒理学、接触/剂量、TK和MOA数据的综合分析表明MTBE对人类的致癌和非致癌风险很小。

Methyl-tert-butyl ether (MTBE) is a fuel oxygenate used in non-United States geographies. Multiple health reviews conclude that MTBE is not a human-relevant carcinogen, and this review provides updated mode of action (MOA), exposure, dosimetry and risk perspectives supporting those conclusions. MTBE is non-genotoxic and has large margins of exposure between blood concentrations at the overall rat 400 ppm inhalation NOAEL and blood concentrations in typical workplace or general population exposures. Non-cancer and threshold cancer hazard quotients range from a high of 0.046 for fuel-pump gasoline station attendants and are 100-1,000-fold lower for general population exposures. Cancer risks conservatively assuming genotoxicity for these same scenarios are all less than 1 × 10-6. The onset of MTBE nonlinear toxicokinetics (TK) in rats at inhalation exposures less than 3,000 ppm, a dose that is also not practically achievable in fuel-use scenarios, indicates that high-dose specific male rat kidney and testes (3,000 and 8,000 ppm) and female mouse liver tumors (8000 ppm) are not quantitatively relevant to humans. Mode of action analyses also indicate MTBE male rat kidney tumors, and lesser so female mouse liver tumors, are not qualitatively relevant to humans. Thus, an integrated analysis of the toxicology, exposure/dosimetry, TK, and MOA data indicates that MTBE presents minimal human cancer and non-cancer risks.