Petroleum refiners were not required to use any particular oxygenate in RFG, but by the late s, a petroleum product, methyl tertiary butyl ether MTBE , was used in 87 percent of RFG due to its ease of transport and blending. In the Midwest, ethanol was a more common component of RFG. Despite its success at reducing ozone precursors, MTBE was phased out of the gasoline pool due to concerns over its solubility in water, which resulted in the contamination of water resources in numerous states.
Currently, 30 percent of gasoline sold in the United States is reformulated gasoline. Ethanol is providing the additional octane required by RFG. At the time, the U. At the same time, EPA and the U. The BTEX complex is a hydrocarbon mixture of benzene, toluene, xylene and ethyl-benzene. Commonly referred to as gasoline aromatics, these compounds are refined from low-octane petroleum products into a high-octane gasoline additive.
While some volume of BTEX is native to gasoline, it is also added to finished gasoline to boost its octane rating. The total volume of BTEX aromatics in finished gasoline depends on the desired octane value and other desired fuel properties. When faced with the removal of lead as the primary octane provider in gasoline, refiners had two available alternatives, BTEX and ethanol. The refining industry invested in additional refining capacity to replace lead with BTEX, a high-octane petroleum refining product.
As a result of its substitution for lead, BTEX volume rose from 22 percent to roughly a third of the gasoline pool by In premium gasoline grades, the BTEX volume content was as high as 50 percent. In mandating cleaner fuels, through reformulated gasoline and other programs, EPA has reduced the volume of aromatics to between 25 to 28 percent of the conventional gasoline pool, though some health professionals question the safety of even these levels.
After the lead phase-out, there were early concerns regarding the BTEX complex. Today, health research indeed suggests that even very low-level exposure to the BTEX complex, from gasoline additives and other petroleum products, may contribute to negative developmental, reproductive and immunological responses, as well as cardio-pulmonary effects.
Upon incomplete combustion of the BTEX complex contained in gasoline, ultra-fine particulates UFP and polycyclic aromatic hydrocarbons PAHs are formed, which carry their own adverse health impacts even at low levels. Both UFP and PAHs have also been linked to developmental and neurodegenerative disorders, cancers, and cardio-pulmonary effects. Considerable attention has been given to benzene in fuel, as it is highly toxic. At the same time, the partial replacement of benzene with other aromatic compounds xylene, ethyl-benzene, toluene may not be sufficient in reducing exposure to BTEX's toxic effects.
The other aromatics, such as toluene and xylene, are not capped. In addition, all the drivers tested showed trace amounts of lead in their blood. But a low level of lead could be tolerated, the scientists announced. That report acknowledged that exposure levels might rise over time. The effects of so much lead being burned and forced into the air are still being felt in the United States and other countries where leaded gasoline was—or still is—used.
Research has shown that lead exposure in children is linked to "a whole raft of complications later in life," writes Kevin Drum for Mother Jones , among them lower IQ, hyperactivity, behavioral problems and learning disabilities.
A significant body of research links lead exposure in children to violent crime, he writes. New Cars. Buyer's Guide. Type keyword s to search. Today's Top Stories. You may be able to find more information about this and similar content at piano.
They tangled around his neck, and killed him. The fatal attraction of lead. Did removing lead from petrol spark a decline in crime? Does lead poisoning make you violent? Image source, Science Photo Library.
Chemist Thomas Midgley insisted that tetraethyl lead was safe. Only 49 people worked there. An aerial photograph of DuPont's Deepwater factory site, where tetraethyl lead was developed. Chemist Thomas Midgley with the Delco laboratory test engine. Risky, but useful? Image source, Alamy. Dr Alice Hamilton argued the benefits of adding lead to petrol were outweighed by the risks.
Pollution v progress. The Roman civil engineer Vitruvius warned against the dangers of lead 2, years ago. However, it was not the only way to solve the problem. The crime connection. Disputed science and delayed regulation. How did the US get this so wrong for so long? Asbestos continued to be widely used in construction despite the emerging evidence of its dangers. More from Tim Harford:. Related Topics. Published 12 October Published 21 April Published 9 January
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