Methyl Tertiary-Butyl Ether Exposure from Gasoline in the U.S. Population, NHANES 2001–2012

BACKGROUND: Methyl tertiary-butyl ether (MTBE) was used as a gasoline additive in the United States during 1995–2006. Because of concerns about potential exposure and health effects, some U.S. states began banning MTBE use in 2002, leading to a nationwide phaseout in 2006. OBJECTIVES: We investigated the change in blood MTBE that occurred during the years in which MTBE was being phased out of gasoline. METHODS: We used data from the National Health and Nutrition Examination Survey (NHANES) from 2001–2012 to assess the change in blood MTBE over this period. We fit sample-weighted multivariate linear regression models to 12,597 human blood MTBE concentrations from the NHANES 2001–2002 to 2011–2012 survey cycles. RESULTS: The unweighted proportion of the individuals with MTBE blood levels above the limit of detection (LOD) of [Formula: see text] was 93.9% for 2001–2002. This portion dropped to 25.4% for the period 2011–2012. Weighted blood MTBE median levels (ng/L) (25th and 75th percentiles) decreased from [Formula: see text] for the period from 2001–2002 to [Formula: see text] for the period from 2005–2006. For the entire postban period (2007–2012), MTBE median levels were below the detection limit of [Formula: see text]. DISCUSSION: These decreases in blood MTBE coincided with multiple statewide bans that began in 2002 and a nationwide ban in 2006. The multivariate log-linear regression model for the NHANES 2003–2004 data showed significantly higher blood MTBE concentrations in the group who pumped gasoline less than 7 h before questionnaire administration compared to those who pumped gasoline more than 12 h before questionnaire administration ([Formula: see text]). This study is the first large-scale, national-level confirmation of substantial decrease in blood MTBE levels in the general population following the phaseout of the use of MTBE as a fuel additive. https://doi.org/10.1289/EHP5572