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Normally we don’t question the health implications of the fuel we put in our vehicles. As long as we put the fuel in our cars as opposed to our mouths, all types of fuel seem “safe”.
But what does safe mean? Does “safe” mean that we fill our vehicles and drive away without immediate devastating side effects, or does “safe” mean that exposure to fuel droplets and vapors over several decades has zero adverse effects?
The first definition of “safe” is pretty easy to evaluate. Indeed, if you are reading this column, you most likely surpassed that safety threshold. The second definition is much harder to evaluate independently, but several well-executed studies have been performed on numerous fuels and fuel additives. In fact, these studies have historically driven many fuel composition changes.
Pure gasoline contains hundreds of molecular compounds, all combinations of carbon and hydrogen atoms. Properties of a fuel — such as octane, volatility, energy content, and carbon-based emissions propensity — are dictated by the combination of molecular compounds selected. Well-known fuel molecules such as hexane and heptane will make you very sick if you drink them, but there are no known health issues associated with casual exposure. Other fuel molecules such as benzene and toluene are known carcinogens, which dramatically increase the likelihood of cancer with prolonged casual exposure.
So, where does bioethanol fit in this discussion? The figure below lists several gasoline constituents and additives that have been used historically to increase octane to the required levels. Hexane and heptane are iso-alkanes, a “safe”.hydrocarbon but relatively low octane. A fuel consisting solely of iso-alkanes would satisfy octane requirements and be “safe” but be extremely expensive because the fuel produced from a barrel of oil would decrease significantly.
Benzene and toluene are a class of hydrocarbon molecules called aromatic hydrocarbons, most of which have been proven carcinogenic. They are high-octane and have a high energy density, which are desirable attributes, but are definitely not “safe”.
Tetraethyl lead (TEL) is a great octane additive and relatively inexpensive, but lead has been a known brain toxin for decades and is banned in most consumer products, including gasoline.
Methyl tertiary butyl ether (MTBE) is good for octane and fairly inexpensive, but it is toxic and dissolves fully in water — a bad combination! Leaks of MTBE into groundwater, lakes, or rivers mix with water and cannot be removed, creating a mixture toxic to fish and humans. Other additives, such as methanol, have this same issue.
What about bioethanol? There are no known adverse health consequences associated with prolonged exposure. You can even ingest limited amounts and won’t be harmed, although you may do or say something you regret the next day. Every other known high-octane constituent may seriously harm you in one way or another. The cause of harm will vary, but the end result in all cases is problematic.
In conclusion, bioethanol is the only high-octane fuel constituent known without associated adverse health effects from prolonged exposure. Bioethanol is safe. In fact, it is the only safe choice.
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