Methyl tertiary-butyl ether (MTBE) is one of various additives used to oxygenate gasoline. These substances are blended with gasoline to reduce carbon dioxide emissions (MTBE also reduces other toxic chemical compounds in vehicle emissions). MTBE has been in use since 1979, primarily in response to the diminishing use of lead in gasoline.

In 1990, with the passage of the Clean Air Act Amendments (specifically Section 211), the use of oxygenated gas was required in areas with excessive levels of CO air pollution. These areas were primarily urban, meaning that huge numbers of individuals have been exposed to MTBE. The positive aspect of the blend of gasoline and MTBE (which is highly flammable) is that it allows a much cleaner burn and less environmentally harmful emissions. Of the reformulated gasoline (RFG) mandated by this act, over 85% contain MTBE.

According to the Environmental Protection Agency (EPA), although the use of MTBE appears noble, its use has caused many health and safety concerns for people who are exposed to it.

Not only can individuals suffer health risks by inhaling MTBE, but the contamination of potable water stores, and thus ingestion, are other very real concerns. Water contamination can happen through the leakage from gasoline storage or transport units, most of which are located underground.

MTBE has a very high level of solubility and there have been many incidences of water contamination all over the country, especially in places of high population density (such as California and New England). While MTBE is absorbed quickly into water, it is not similarly easy to separate from water as it is not readily biodegradable. On the other hand, in air, it quickly evaporates and produces a vapor which has a very distinct, unpleasant odor. Breathing this vapor can result in discomfort as described below under symptoms.

The National Center for Environmental Health (a branch of the Centers for Disease Control) suggests that people who concerned about overexposure to MTBE through inhalation or water contamination contact a state drinking water agency immediately. Potential exposure is at times identified by the strong smell and may or may not be indicative of harmful levels. Exposure to MTBE can be confirmed because it is detectable in the bloodstream, as well as breath and urine, for up to two days after contact.

While not considered as dangerous as Benzene (an element that MTBE replaces in gasoline) MTBE is a carcinogen at high enough exposure levels, as shown by laboratory experiments on animals conducted by the CDC. However, no governmental bodies have claimed to find sufficient evidence to recognize MTBE as a possible human carcinogen. Part of this reasoning is that it is eventually broken down and removed from the body, thus long term accumulation is not a risk.

Since humans do not encounter MTBE as a separate entity from gasoline, very few concrete conclusions have been drawn since a causal relationship cannot be adequately established between the chemical and health conditions.

Specifically, the Agency for Toxic Substances and Disease Registry (ATSDR) has still reserved a definitive judgment on the adverse health effects of MTBE. Many other studies have been conducted though and indicate that the following are symptoms found after contact with MTBE.
Symptoms from inhalation include:

* Headaches

* Cough

* Nose or throat burning

* Other respiratory irritation

* Lightheadedness

* Eye irritation

* Nausea

* Vomiting

* Dizziness, "spaciness" or disorientation

Possible health issues resulting from ingestion or dermal contact (i.e. drinking, swimming or showering) include:

* Gastrointestinal irritation

* Liver and kidney damage and possibly liver and kidney cancer

* Nervous system effects ranging from hyperactivity and
incoordination to convulsions and unconsciousness

* Risks to healthy fetal development

Obviously, at the expense of the health of the general public, requiring oxygenating additives in gasoline has been a mixed blessing. Indeed, before the federal government suggested the use of MTBE, and before gas and oil companies began adding it, more research should have been done as to its effects on the environment and human health.