MTBE

City of San Marcos

MTBE was used as gasoline oxygenation additive to boost the octane number. In 2005, MTBE was replaced by ethanol as a gasoline additive. MTBE causes cancers in rats.

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Samples

Samples exceeding legal limit (MCL)

Samples exceeding
health guidelines

Testing results - average by year

Year	Average result	Samples taken	Range of results
2014	ND	5	ND
2015	ND	6	ND
2016	ND	6	ND
2017	ND	7	ND
2018	ND	6	ND
2019	ND	6	ND

ppb = parts per billion

State and national drinking water standards and health guidelines

EWG Health Guideline 13 ppb

The EWG Health Guideline of 13 ppb for MTBE was defined by the California Office of Environmental Health Hazard Assessment as a public health goal, the level of a drinking water contaminant that does not pose a significant health risk. This health guideline protects against cancer.

ppb = parts per billion

All test results

Date	Lab ID	Result
2014-03-12	AC63077	ND
2014-08-12	AC63071	ND
2014-08-12	AC63073	ND
2014-08-12	AC63087	ND
2014-08-12	AC63075	ND
2015-06-10	AC95472	ND
2015-06-10	AC95470	ND
2015-06-10	AC95474	ND
2015-06-10	AC95468	ND
2015-09-23	AD08299	ND
2015-09-23	AD08303	ND
2016-03-16	AD29111	ND
2016-09-16	AD49839	ND
2016-11-28	AD59222	ND
2016-11-28	AD59220	ND
2016-12-12	AD61688	ND
2016-12-12	AD61664	ND
2017-02-22	AD71534	ND
2017-05-03	AD82464	ND
2017-05-03	AD82462	ND
2017-05-03	AD82466	ND
2017-05-03	AD82468	ND
2017-07-12	AD89095	ND
2017-10-12	AE00574	ND
2018-01-25	AE10638	ND
2018-01-25	AE10564	ND
2018-01-25	AE10572	ND
2018-01-25	AE10574	ND
2018-04-11	AE22067	ND
2018-07-26	AE34698	ND
2019-01-16	AE50162	ND
2019-01-16	AE50166	ND
2019-01-16	AE50168	ND
2019-01-16	AE50164	ND
2019-04-16	AE62552	ND
2019-07-09	AE73687	ND