On March 17, comments closed on EPA’s proposal to lower the ozone limit from 75 parts per billion (ppb) to somewhere between 65 to 70 ppb. In comments to the agency, EESI fully supported the agency’s lowering of the 8-hr standard for ozone, but asked the agency to consider more fully the role that fuel quality may play in the formation of ozone precursors and other air toxics. Additionally, EESI raised concerns about potential flaws in the newly redesigned modelling tool that state regulators are required to use when crafting their State Implementation Plans (SIPs) for ozone and other criteria air pollutants.
Ozone, commonly referred to as smog, is a complex mixture formed when air pollutants react with each other in the presence of sunlight. In the stratosphere, ozone prevents harmful ultraviolet light from reaching the earth's surface. But ground level ozone impairs lung functioning and contributes to increased incidences of asthma and other lung diseases, especially among children and the elderly. The 8-hr ozone standard was set at 75 ppb in 2008. According to EPA, the negative health impacts of ozone at this level has become clearer since that time.
In the United States, tremendous progress has been made from the smoggy cityscapes of the 1960s and 70s, but even still, EPA estimates that 45 million people live, work or attend school within 300 feet of a major road, airport or railroad. At the same time, there is mounting evidence of the negative health impacts of living or working close to these busy roadways.
EPA’s ozone proposal will reduce the allowable limit of ozone precursors, such as volatile organic compounds (VOCs) and nitrogen dioxide (NOx) from agriculture, industry, and power plants to reduce these precursors. While lowering ozone levels from these sources will protect human health, EESI cautioned that the largest contributor to ground level ozone in urban areas, gasoline exhaust, is not considered in the rule. Therefore, a much bigger benefit to health could be realized by tackling this pernicious source of toxins.
While vehicle technology has greatly improved over the past decade – the quality of the fuel used has changed little. When lead was phased out of gasoline by the 1990 Clean Air Act Amendments, its replacement was already a known toxin. Today, each gallon of gasoline contains 25 to 30 percent by volume of gasoline aromatics. These volatile organic compounds are composed primarily of benzene, toluene, ethyl-benzene and xylene (BTEX).
Not only is the BTEX complex itself a known toxin, it contributes greatly to tailpipe emissions of fine (PM2.5) and ultra-fine (UFP) particles as well as polycyclic aromatic hydrocarbons (PAHs). PAHs have been linked to greater incidences of developmental disorders such as autism and ADHD. Ultra-fine particles are able to penetrate deep into the lungs and travel into the bloodstream; UFP exposure has also been linked to thickening of the arterial walls and stimulus of the central nervous system.
Today, there are two available sources of octane for vehicles – gasoline aromatics, or biofuels. Increasing the amount of aromatics would increase tailpipe emissions of ozone precursors and other air toxics. Conversely, biofuels are both a cheaper and cleaner form of octane. Splash blending of ethanol has already allowed refineries to reduce the amount of aromatics in the gasoline supply, therefore lowering their contribution to tailpipe emissions.
Therefore, EESI urges the EPA to consider the role of gasoline aromatics, in both ozone formation and other criteria air pollutants. Addressing fuel quality would provide great benefit to the health of children’s developing bodies, and help us all breathe a lot easier.
For more information see:
Gasoline Aromatics – A Toxic Brew that Surrounds Us All, EESI