jueves, 20 de septiembre de 2012

MTBE & Cancer


EPA Draft Says MTBE a 'Likely' Cause of Cancer

Chicago its has 0.8% of MTBE in gasolines
Mexico City it has 8% of MTBE in gasolines




CONTACT: Bill Walker, (510) 444-0973 x301; EWG Public Affairs, (202) 667-6982
FOR IMMEDIATE RELEASE: July 11, 2005
WASHINGTON, July 11 — A EPA draft risk assessment says MTBE, the gasoline additive that has contaminated drinking water in at least 29 states, is a "likely" human carcinogen, according to agency sources.

An EPA official who reviewed an earlier version of the document told Environmental Working Group (EWG) that the risk assessment's most notable finding for the first time links MTBE to cancers such as leukemia and lymphoma, with toxicological endpoints similar to known carcinogens such as benzene and butadiene. Previously, EPA had classified MTBE as a "possible" cause of cancer, and concerns about contamination centered on the fact that in small doses its foul stench renders water undrinkable.

The EPA official said the document's authors completed their draft more than a year ago. It has been circulating within the agency for review and has already been approved by the Office of Research and Development's National Center for Environmental Assessment. Once all EPA divisions have signed off on it, it must still go through external review.

"People have been trying to get this out of the agency forever," said the official.

If approved, the finding will rock the current debate in Congress over whether the oil companies who make and use MTBE should be held responsible for cleaning up drinking water contaminated by the chemical leaking from underground gasoline storage tanks. According to state water agencies' records compiled by EWG, MTBE has been detected in more than 1,800 water systems across the country.

The American Water Works Association and the Association of Metropolitan Water Agencies released studies last month estimating nationwide cleanup costs at between $25 billion and $33 billion, and possibly reaching $85 billion. The finding that MTBE is a likely carcinogen would add urgency to cleanup efforts, causing costs to soar.

The House has passed an energy bill, pushed by Majority Leader Tom DeLay of Texas, that would bar communities and water systems from suing MTBE makers for knowingly manufacturing and distributing a defective product — even though documents from two California lawsuits show the oil industry knew as early as 1979 that the compound was a threat to water supplies but still pushed for its use as a gasoline additive to make fuel burn cleaner.

"We knew the idea to exempt MTBE makers from lawsuits was bad news for taxpayers. Now EPA is learning how dangerous it would be for public health," said EWG President Ken Cook. "No matter how the risk assessment finally comes out, this is clearly not the time to be letting the makers of this chemical off the hook."


Methyl tert-butyl ether

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Methyl tert-butyl ether
Identifiers
CAS number 1634-04-4 YesY
PubChem 15413
ChemSpider 14672 YesY
KEGG C11344 YesY
ChEBI CHEBI:27642 YesY
Jmol-3D images Image 1
Properties
Molecular formula C5H12O
Molar mass 88.15 g mol−1
Density 0.7404 g/cm³
Melting point -109 °C, 164 K, -164 °F
Boiling point 55.2 °C, 328 K, 131 °F
Solubility in water 26 g/L (20 °C)[1]
Hazards
NFPA 704
NFPA 704.svg
3
1
0
Flash point −10 °C (14 °F)
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references
Methyl tert-butyl ether, also known as methyl tertiary butyl ether and MTBE, is an organic compound with molecular formula (CH3)3COCH3. MTBE is a volatile, flammable, and colorless liquid that is sparingly soluble[1] in water. It has a minty odor vaguely reminiscent of diethyl ether, leading to unpleasant taste and odor in water. MTBE is a gasoline additive, used as an oxygenate to raise the octane number. Its use is controversial in the US and declining in that country in part because of its occurrence in groundwater and legislation favoring ethanol. Worldwide production of MTBE has been constant at about 18 million tons/y (2005) owing to growth in Asian markets which are less subject to ethanol subsidies.[2]

Contents

 [hide] 

Production and properties

MTBE is manufactured via the chemical reaction of methanol and isobutylene. Methanol is derived from natural gas, and isobutylene is derived from butane obtained from crude oil or natural gas, thus MTBE is derived from fossil fuels. In the United States, it was produced in very large quantities (more than 200,000 barrels (32,000 m3) per day in 1999) during its use as a fuel additive.

Uses

MTBE is almost exclusively used as a fuel component in fuel for gasoline engines. It is one of a group of chemicals commonly known as oxygenates because they raise the oxygen content of gasoline.

As anti-knocking agent

In the US it has been used in gasoline at low levels since 1979 to replace tetraethyl lead and to increase its octane rating helping prevent engine knocking. Oxygenates help gasoline burn more completely, reducing tailpipe emissions from pre-1984 motor vehicles; dilutes or displaces gasoline components such as aromatics (e.g., benzene) and sulfur; and optimizes the oxidation during combustion. Most refiners chose MTBE over other oxygenates primarily for its blending characteristics and low cost.

Alternatives to MTBE as an anti-knock agent

Other compounds are available as additives for gasoline including ethanol and some ethers such as tert-amyl methyl ether (TAME).
Ethanol has been advertised as a safe alternative by the agricultural and other interest groups in the USA and Europe. It has been proposed that as a polar solvent, ethanol may separate nonpolar hydrocarbons from the gasoline, a problem that MTBE does appear to cause. Some volatile hydrocarbons in gasoline vapors are carcinogens, and gasoline vapors produce photochemical smog. Ethanol's higher cost requires government intervention in the form of subsidies or mandated usage to be competitive. In 2003, California was the first U.S. state to start replacing MTBE with ethanol. Several other states started switching soon thereafter.
Advocates of both sides of the debate in the United States sometimes claim that gasoline manufacturers have been forced to add MTBE to gasoline by law. It might be more correct to say they have been induced to do so, although any oxygenate would fulfill the law.
An alternative to straight ethanol is the related ether ETBE, which is manufactured from ethanol and isobutene. Its performance as an additive is similar to MTBE, but due to the higher price of ethanol compared to methanol, it is more expensive.
Higher quality gasoline is also an alternative, i.e., so that additives such as MTBE are unnecessary. Iso-octane itself is used. MTBE plants can be retrofitted to produce iso-octane from isobutylene.[3],[4]

As a solvent

As a solvent, MTBE possesses one distinct advantage over most ethers - it has a reduced tendency to form explosive organic peroxides. Opened bottles of diethyl ether or THF can build up dangerous levels of these peroxides in months, whereas samples of MTBE are usually safe for years (but they should still be tested periodically). For this reason (as well as its higher boiling point), MTBE is used as a solvent extensively in industry, where safety concerns and regulations make working with diethyl ether, THF, or other ethers much more difficult and expensive. However, despite the popularity of MTBE in industrial settings, it is rarely used as a solvent in academia with some exceptions.[5]
MTBE forms azeotropes with water (52.6 °C; 96.5% MTBE).[6] and methanol (51.3 °C; 68.6% MTBE).[7]
Although an ether, MTBE is a poor Lewis base and does not support formation of Grignard reagents. It is also unstable toward strong acids. It reacts dangerously with bromine.[8]

Persistence and pervasiveness in the environment

MTBE gives water an unpleasant taste at very low concentrations, and thus can render large quantities of groundwater non-potable. MTBE is often introduced into water-supply aquifers by leaking underground storage tanks (USTs) at gasoline stations or by gasoline containing MTBE spilled onto the ground. The higher water solubility and persistence of MTBE cause it to travel faster and farther than many other components of gasoline when released into an aquifer.[9][10]
MTBE is biodegraded by the action of bacteria. In the proper type of bioreactor, such as a fluidized bed bioreactor, MTBE can be rapidly and economically removed from water to undetectable levels. Activated carbon produced from coconut shells and optimized for MTBE adsorption can also reduce MTBE to undetectable levels.[11]

Health risks

According to the IARC, a cancer research agency of the World Health Organization, MTBE is not classified as a human carcinogen. MTBE can be tasted in water at concentrations of 5 – 15 µg/l.[12]
As of 2007, researchers have limited data about the health effects of ingestion of MTBE. The United States Environmental Protection Agency (EPA) has concluded that available data are inadequate to quantify health risks of MTBE at low exposure levels in drinking water, but that the data support the conclusion that MTBE is a potential human carcinogen at high doses.[13]

Legislation and litigation in the U.S.

Main article: Methyl tert-butyl ether controversy
MTBE removal from groundwater and soil contamination in the U.S. is estimated to cost from $1 billion[14] to $30 billion,[15] including removing the compound from aquifers and municipal water supplies and replacing leaky underground oil tanks. In one case, the cost to oil companies to clean up the MTBE in wells belonging to Santa Monica is estimated to exceed $200 million.[16] In another case, the City of New York estimated a $250 million cost for cleanup of a single wellfield in Queens, NY.[17]
MTBE is banned in the US states of California and New York, starting January 1, 2004. As of September 2005, twenty-five states had signed legislation banning MTBE. (A table of state by state information, as of 2002, is available at the United States Department of Energy website.[18])
In 2000, the U.S. EPA drafted plans to phase out the use of MTBE nationwide over four years. As of fall 2006, hundreds of lawsuits are still pending regarding MTBE contamination of public and private drinking water supplies.
The Energy Policy Act of 2005, passed in the U.S. House of Representatives, did not include a provision for shielding MTBE manufacturers from water contamination lawsuits. This provision was first proposed in 2003 and had been thought by some to be a priority of Tom DeLay and Rep. Joe Barton, then chairman of the Energy and Commerce Committee.[19] This bill did include a provision that gives MTBE makers, including some major oil companies, $2 billion in transition assistance as MTBE is phased out over the next nine years.[20] Due to opposition in the Senate,[21] the conference report dropped all MTBE provisions. The final bill was passed by both houses and signed into law by President Bush.[22] The lack of MTBE liability protection is resulting in a switchover to the use of ethanol as a gasoline additive. Some traders and consumer advocates are blaming this for an increase in gasoline prices.[23]
The U.S. EPA currently lists MTBE as a candidate for a maximum contaminant level (MCL) in drinking water.[24] MCLs are determined by the EPA using toxicity data.

See also

References

  1. ^ a b Record in the GESTIS Substance Database from the IFA
  2. ^ M. Winterberg, E. Schulte-Korne, U. Peters, F. Nierlich "Methyl Tert-Butyl Ether" in Ullmann's Encyclopedia of Industrial Chemistry, 2010, Wiley-VCH, Weinheim. doi:10.1002/14356007.a16_543.pub2
  3. ^ http://www.nesteengineering.com/default.asp?path=111,360,362,477
  4. ^ http://www.halliburton.com/kbr/hydroChem/petroChem/nexoctane.jsp
  5. ^ http://www.jlr.org/cgi/content/abstract/D700041-JLR200v1
  6. ^ Zeon Corportation
  7. ^ CRC Handbook of Chemistry and Physics, 90th edition
  8. ^ "Interaction between bromine and tert-butyl methyl ether". http://www.crhf.org.uk/incident09.html. Retrieved 13 May 2010. 
  9. ^ http://www.handpmg.com/lustline31-mtbe-or-benzene.htm
  10. ^ San Francisco Bay Area Regional Water Quality Control Board Integrated Basin Management Plan (2004)
  11. ^ link text
  12. ^ Fischer A, Oehm C, Selle M, Werner P. (2005). "Biotic and abiotic transformations of methyl tertiary butyl ether (MTBE)". Environ Sci Pollut Res Int 12 (6): 381–6.. doi:10.1065/espr2005.08.277. PMID 16305145. 
  13. ^ http://www.epa.gov/mtbe/faq.htm#concerns
  14. ^ SIGMA - Weekly Report
  15. ^ Long Island Utility Fighting to Defeat MTBE Safe Harbor - Napoli Bern - Attorneys
  16. ^ AmeriScan: February 17, 2005
  17. ^ Navarro, Mireya (2009-10-20). "City Awarded $105 Million in Exxon Mobil Lawsuit". The New York Times. http://www.nytimes.com/2009/10/20/science/earth/20exxon.html. Retrieved 2010-05-12. 
  18. ^ Website U.S. Department of Energy
  19. ^ http://www.cnn.com/2005/POLITICS/04/21/energy.bill.mtbe.ap/
  20. ^ http://www.msnbc.msn.com/id/7574562/+MTBE&hl=en
  21. ^ Charles Babington, House Again Passes GOP Energy Measures, Washington Post, June 16, 2004, at A4 (House passes Energy Bill, but Senate opponents of MTBE provision in House Bill have the votes to prevent its enactment).
  22. ^ http://thomas.loc.gov/cgi-bin/bdquery/z?d109:h.r.00006:
  23. ^ prices ethanol/index.htm?cnn=yes http://money.cnn.com/2006/04/18/news/economy/gas prices ethanol/index.htm?cnn=yes
  24. ^ CCL 2 List

External links


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