The Environmental and Energy Study Institute (EESI) held a briefing examining the health impacts of current octane sources and the need for cleaner, cost-effective octane providers. Octane is necessary for vehicle performance and increasing octane volumes would enable highly efficient engines. At the same time, octane-boosters in use today have historically been highly toxic compounds. But cleaner alternatives are available—namely biofuels.

Octane was provided by lead until EPA phased out its use because of serious health issues. Today, there are two primary sources of octane: gasoline aromatics (a petroleum refinery product) and ethanol (a biofuel). Gasoline aromatics make up approximately 25 percent of gasoline volume and are composed of benzene, ethyl-benzene, toluene and xylene – commonly referred to as the BTEX complex.

As well as being toxic itself, the BTEX complex contributes to the formation of secondary air pollutants, including ultrafine particulate matter (UFP) and polycyclic aromatic hydrocarbons (PAHs). Numerous health studies have linked both tailpipe exhaust and the BTEX complex to serious developmental and many chronic health conditions. As carmakers look for additional sources of octane, the impacts to both health and the environment need to be considered.

Research is finding that high octane fuel blends, such as a mid-level biofuel blend (30 percent ethanol and 70 percent gasoline), may enable greater engine efficiencies, lower GHG emissions and improve fuel economy. Substituting cleaner forms of octane into fuel will have the added benefit of improving air quality.

As automotive manufacturers look towards meeting stringent fuel economy standards, the role of fuels is receiving fresh attention. Automotive manufacturers, fuel producers and the Department of Energy (DOE) are collaborating on a project that assesses the potential co-optimization of fuels and engines in new cars through the DOE’s Optima program.

Optima aims to reduce per vehicle petroleum consumption by 30 percent beyond currently mandated engine efficiency measures by 2030. DOE expects to achieve this reduction through a combination of engine technologies and by increasing the use of highly efficient, cleaner forms of octane. Reducing gasoline consumption is critical since the transportation sector is responsible for 27 percent of greenhouse gas (GHG) emissions, as well as half of all toxic emissions in the United States.

  • Dr. Carol Kwiatowski, Executive Director, The Endocrine Disruption Exchange, explained that BTEX, which is added to gasoline to boost its octane value, is an acronym for four chemicals: benzene, toluene, ethylbenzene and xylene, all classified as hazardous air pollutants by EPA. She noted that if there is one takeaway from this briefing, it is that these chemicals are in the air, most of us are exposed to them on a regular basis, and they’re probably making us sick. According to Dr. Kwiatowski, low-level exposure to hormone-disrupting chemicals, including BTEX, is a public health threat on the scale of climate change.
  • BTEX is a petroleum product and is used in numerous consumer products including gasoline, detergents, air fresheners, toys, playground equipment, and many more common products. These compounds become air pollutants when they are released from tailpipe emissions, gas pump emissions, fossil fuel extraction, cigarette smoke and the use of household products. Ninety percent of BTEX in outdoor air is from mobile sources, such as cars and trucks.
  • Most studies of the BTEX complex are at high exposure levels. At such levels, the BTEX complex is carcinogenic, can affect development and reproduction, and even cause death directly. But low-level prenatal and early childhood exposure can also be very harmful, causing permanent, lifelong endocrine disruption. This disrupts growth, aging, cardiovascular function, behavior and many other biological functions.
  • BTEX is readily found in blood and urine samples from the general population, and even in the umbilical cords of babies. Ninety percent of the time, ambient air contains BTEX at low concentrations. There’s been little study of the effects of this low-level exposure to BTEX.
  • To address this research gap, The Endocrine Disruption Exchange conducted a review of 42 health studies, 35 of which focused on the health effects of benzene, 17 on toluene, 12 on ethylbenzene, and 16 on xylene. Benzene isn’t the most toxic of the four chemicals, but it is the most studied.
  • All the chemicals were associated with multiple negative health impacts, including reduced birth weight, which has negative health consequences throughout life (it is linked to asthma and heart defects). The chemicals were also linked to reduced head size at birth, reduced sperm count, and compromised immune systems.
  • Are EPA’s ‘safe levels’ really safe? The studies found that even a one microgram change in the concentration of BTEX can improve the odds of avoiding birth defects. EPA acceptable levels are significantly above what studies indicate are levels at which health problems begin.
  • Dr. Kwiatowski's organization recommends limiting or removing BTEX from consumer products and transportation fuels, and replacing it with chemicals that have no biological activity. Since BTEX does not stay in the body like lead and other chemicals do, phasing it out will quickly do a great deal to mitigate negative health consequences.


  • Dean Drake, President, Defour Group LLC; retired General Motors engineer (34 years), explained that gasoline today is a mixture of 10 percent ethanol and 90 percent gas. This increased use of ethanol in gasoline is a change that has largely gone unnoticed by consumers. The Renewable Fuel Standard has greatly driven up ethanol consumption.
  • Refineries produce a sub-octane blend stock that gets sold to blenders, who then add ten percent ethanol to it to produce market-grade gasoline. Ethanol has an extremely high octane rating.
  • Studies show that ethanol has made gasoline less expensive since the end of 2011. Counterintuitively, this is due to the removal of ethanol subsidies and trade barriers, which forced the ethanol refining industry to increase its efficiency levels. Before 2011, ethanol cost more than gasoline; since then, it has cost less.
  • E10 saves consumers four cents per gallon, on average, according to the Defour Group's study. That adds up to $4-5 billion dollars a year in consumer savings.
  • The environmental impact of ethanol is in dispute. Drake said recent testing of ethanol fuel blends by EPA and the oil industry (the EPAct study) suffered from methodological problems and so did not resolve the uncertainty. EPAct tested 200 blends of fuel, but none of the fuels matched the fuels that are sold to the public, and the study may misattribute air pollutants to ethanol. This is significant because these results are being used by the MOVES2014 Model, which state air regulators use to model air quality. The net effect of this new model is to disincentivize the use of higher ethanol blends, despite the fact that such blends have been found to improve air quality. Drake said the EPA model needs to be corrected to provide more accurate information.
  • If we’re going to make further progress on reducing carbon emissions, we need higher efficiency engines, which require higher octane fuels. The oil industry’s solution is to sell today’s expensive, premium fuels. The alternative is a 25-30 percent ethanol blend, which is a high-octane fuel that would cost less than today's regular 87 octane gasoline. To make E30, the oil industry doesn’t have to do anything but offer its same feedstock to blenders.
  • Vehicle manufacturers can make highly efficient cars that can handle E30. But to do so, lower octane fuels (85 and 87 octane) need to be phased out, because they would be incompatible with highly efficient engines.


  • Reuben Sarkar, Deputy Assistant Secretary for Transportation, U.S. Department of Energy, reiterated that achieving better fuel economy is limited by the lack of high-octane fuels on the market.
  • DOE has a goal of bringing better vehicles with better fuel economy to consumers quickly. Internal combustion engines will be around for decades to come, despite gains in the electric vehicle sector, which makes it important to increase their fuel efficiency.
  • Higher efficiency, lower emission engines are possible today. Generally, fuel constrains the engine’s design. Engines are designed to work with the lowest common denominator available on the market (85 octane in the United States), bringing down performance for everybody.
  • By boosting the octane value in fuel by just ten points, you get a significant boost in the amount of efficiency you can build into an engine.
  • The key is to design fuels and engines together, to co-optimize performance.
  • It takes 17 years to turn over the U.S. vehicle fleet. To have a new fleet by 2050, we need to introduce new technologies by 2030, and, therefore, we need additional R&D on new technologies now.
  • “Optima” is a public-private initiative to determine the best fuel that can be designed based on about 50 performance criteria. The goal is to find out what aspects of fuel performance are most important to optimize, carry out an objective scientific study, and then look at scalability, environmental impacts, health impacts, etc.
  • The DOE knows mid-level ethanol blends are a good choice, but its researchers are also looking into other renewable and petroleum-based low greenhouse gas fuel blends.
  • Optima is the fuel equivalent of Energy Star. Very high octane, Optima-branded fuel will be cheaper and cleaner than today's regular gasoline fuel.