Boston Environmental & Engineering Associates, Inc., Waltham, MA, USA.
Gradient, Cambridge, MA, USA.
Risk Anal. 2020 Dec;40(12):2584-2597. doi: 10.1111/risa.13570. Epub 2020 Dec 3.
Methyl tert-butyl ether (MTBE) was added to gasoline in New Hampshire (NH) between 1995 and 2006 to comply with the oxygenate requirements of the 1990 Amendments to the Clean Air Act. Leaking tanks and spills released MTBE into groundwater, and as a result, MTBE has been detected in drinking water in NH. We conducted a comparative cancer risk assessment and a margin-of-safety (MOS) analysis for several constituents, including MTBE, detected in NH drinking water. Using standard risk assessment methods, we calculated cancer risks from exposure to 12 detected volatile organic compounds (VOCs), including MTBE, and to four naturally occurring compounds (i.e., arsenic, radium-226, radium-228, and radon-222) detected in NH public water supplies. We evaluated exposures to a hypothetical resident ingesting the water, dermally contacting the water while showering, and inhaling compounds volatilizing from water in the home. We then compared risk estimates for MTBE to those of the other 15 compounds. From our analysis, we concluded that the high-end cancer risk from exposure to MTBE in drinking water is lower than the risks from all the other VOCs evaluated and several thousand times lower than the risks from exposure to naturally occurring constituents, including arsenic, radium, and radon. We also conducted an MOS analysis in which we compared toxicological points of departure to the NH maximum contaminant level (MCL) of 13 µg/L. All of the MOSs were greater than or equal to 160,000, indicating a large margin of safety and demonstrating the health-protectiveness of the NH MCL for MTBE.
甲基叔丁基醚（MTBE）于 1995 年至 2006 年期间被添加到新罕布什尔州（NH）的汽油中，以符合 1990 年《清洁空气法案》修正案的含氧要求。泄漏的储油罐和溢出的 MTBE 进入地下水，因此 MTBE 已在 NH 的饮用水中被检测到。我们对包括 MTBE 在内的 NH 饮用水中检测到的几种成分进行了比较癌症风险评估和安全边际（MOS）分析。使用标准风险评估方法，我们计算了暴露于 12 种挥发性有机化合物（VOC）（包括 MTBE）和 NH 公共供水系统中检测到的四种天然化合物（即砷、镭-226、镭-228 和氡-222）所带来的癌症风险。我们评估了假设居民摄入水、洗澡时皮肤接触水以及吸入家中水中挥发的化合物等情况的暴露情况。然后，我们将 MTBE 的风险估计与其他 15 种化合物的风险估计进行了比较。根据我们的分析，我们得出的结论是，饮用水中 MTBE 暴露的高风险癌症风险低于评估的所有其他 VOC 的风险，并且比接触天然成分（包括砷、镭和氡）的风险低数千倍。我们还进行了 MOS 分析，将毒理学起点与 NH 的最大污染物水平（MCL）13 µg/L 进行了比较。所有 MOS 均大于或等于 160,000，表明安全边际较大，表明 NH 的 MTBE MCL 对健康具有保护作用。
