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BACKGROUND: Methyl tertiary-hutyl 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 lit 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 1.4 ng/L 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 25.8 (6.08,68.1) ng/L for thc period from 2001-2002 to 4.57 (1.44, 19.1) ng/L for the period from 2005-2006. For thc entire postban period (2007-2012), MTBE median levels were below the detection limit of 1.4 ng/L.

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 (p = 0.032). 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.