Through their contribution to more complete fuel combustion and the dilution of less desirable components fuel ethers make a significant contribution to reducing car pollution.
The environmental benefits of fuel ethers can be divided into two main categories. There are so-called "direct" effects, mainly due to more complete fuel combustion (as a result of organic oxygen presence) and "indirect" ones, coming from the dilution of other, less desirable, gasoline pool components. It is also important to note that their use reduces emissions from all types of gasoline vehicles, regardless of their emission-control technology. Although it seems to be of less importance for EURO IV standard cars with the newest catalyst technology, fuel ethers help to improve combustion for these cars especially in the cold starting phase of the engine, when the catalytic converter is not working.
Direct effects include the reduction of both "regulated" and "unregulated" emissions. Among the specific pollutants already limited by law are carbon monoxide (CO) as well as unburned hydrocarbons (HCs). The second category includes those pollutants that have recently been the focus of attention for the EU authorities, even though they are not yet the subject of legislation. Probably the most important are particulate matter (PM) and ground-level ozone.
Indirect effects lead to reduction of sulphur, olefins, aromatics and benzene levels, regardless of whether the fuel is used in current or older technology vehicles.
The magnitude of the beneficial effects does depend on a number of parameters, such as the percentage of fuel ether actually blended in the petrol, the presence of after-burning catalyst devices, the type and age of the engine or the driving cycle. Nevertheless, there is general agreement in the industrial and scientific community on the following broad values:
- CO emissions decrease is proportional to the fuel ether content in the gasoline.
- Each 1 or 2% of fuel ether produces a 1% reduction in total HC emissions.
- Each 1% of fuel ether results in a 2 to 3% PM emission reduction.
- Fuel ethers generate about half of the ozone when compared to iso/alkylates and one-tenth that of aromatics.
- Each 1% of fuel ether contributes an equivalent percentage reduction in benzene emissions, both evaporative and exhaust.
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In all normal meanings of the word, fuel ethers are certainly safe.
The human health impact of MTBE has been extensively studied, with the first tests screening health risk conducted more than 30 years ago. MTBE has never been classified as toxic or carcinogenic by any regulatory body anywhere in the world.
In addition to research on the possible carcinogenicity of MTBE, there have been numerous toxicological studies none of which indicates that it is a cause for concern. For example, the WHO International Programme on Chemical Safety (IPCS) says that "based on collective evidence, it appears unlikely that MTBE alone induces adverse acute health effects in the general population under common exposure conditions."
The EU has concluded that the ethers ETBE, MTBE and TAME are unlikely to present a hazard to health or the environment under normal handling and use conditions.
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| Do fuel ethers cause cancer ? |
Some media reports have alleged that, based on effects in animal test at very high doses, MTBE is a potential carcinogen. This is not correct. Most of the scientific organisations and all governmental organisations that have evaluated MTBE so far have not classified it as a carcinogen.
The observed effects in animals are species specific for the tested animals and not relevant to humans. In 1998 the International Association of Research on Cancer (IARC), which is a part of the World Health Organisation, classified MTBE in category 3 "not classifiable as to its carcinogenicity to humans".
The US National Toxicology Program, the California Proposition 65 Committee, the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) and the European Union "Working Group on the Classification and Labelling of Dangerous Substances" all decided not to classify MTBE as a substance of concern.
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| Have other ethers been tested ? |
The ethers ETBE, MTBE and TAME have been extensively tested for health and environmental effects. Data for risk assessment purposes according to EU regulations are available including sufficient data on carcinogenic and reproductive effects.
MTBE belongs to the 2% of best tested substances in the world and both ETBE and TAME have robust health and environmental data sets that are sufficient for EU risk assessment purposes.
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| Still, should the Precautionary Principle not dictate that fuel ethers be phased out from gasoline ? |
A key element of the application of the Precautionary Principle is a scientific risk assessment, identifying the degree of scientific knowledge, possible uncertainties, risk acceptability and risk reduction measures. All 3 fuel ethers have or are being subjected to an EU risk assessment demonstrating that no risk for consumers are to be expected. EFOA believes that this objective and scientific process should form the basis on which any further regulation on fuel ethers might be considered.
The Precautionary Principle is a cornerstone for the development of environmental policies in the European Union. EFOA recognises the Principle as an excellent framework for decision-making on solid scientific grounds.
The Precautionary Principle should be applied when there is "sufficient likelihood" that serious or irreversible damage to health or the environment would occur. This is completely in line with the Principle as stated in the Rio Declaration, which calls for a science-based approach with control measures that are commensurate with the defined risk.
A prerequisite for the application of the Precautionary Principle is a scientific risk assessment, identifying the degree of scientific knowledge on the issue in question, possible uncertainties, risk acceptability and risk reduction measures. In the EU, this is a strictly defined and comprehensive process, which will result in regulations that are proportionate to the environmental objectives to be achieved, and will provide a balanced approach to regulation.
It is the most appropriate instrument that will enable the European Union to determine the best course of action concerning the continued usage of fuel ethers in the EU.
All 3 fuel ethers, ETBE, MTBE and TAME have been subjected to the EU risk assessment process to a greater or lesser extent. The Risk Assessment Report for MTBE was finalised and published in the Official Journal of the European Union on 4th December 2001. For TAME this process is nearing its conclusion with the final part of the Risk Assessment report agreed at the March 2005 meeting of the EU Technical Committee on New and Existing Substances. Whilst ETBE due to its growing potential for wide dispersive use as a biofuel has been subject to a call for a reduced data set under Article 12 (2) of the Existing Substances Regulation (EEC No 793/93; Commission Regulation 1217/2002). The completed data set was reviewed by the EU Technical Committee on New and Existing Substances at its November 2005 meeting where it was concluded that it should be regarded as the same as MTBE.
EFOA concurs with the European Commission and other authorities that the Risk Assessment process constitutes the objective and scientific basis on which any further regulation on fuel ethers might be considered.
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