http://www.dri.edu
	Summer 2006

Paying the price at the pump. . . and in other little areas of your world

In 2002, a group of DRI scientists embarked on a $2 million study mandated by the U.S. Environmental Protection Agency and sponsored by the American Petroleum Institute, or API, which is the primary trade organization for the oil and natural gas industry. As part of the Clean Air Act, API must test the health effects of fuels and fuel additives. DRI was contracted to conduct a screening study of personal exposures to evaporative and exhaust emissions from vehicles fueled with baseline and oxygenated gasoline in potentially high-end exposure microenvironments. The study was conducted during winter and summer conditions in three cities: Atlanta—where conventional gasoline is used—and in Chicago and Houston, where ethanol and MTBE are added, respectively, to meet oxygenated fuel requirements.

Mini-van remodel: Jake McDonald, a former graduate student working with DRI, shows off the inside of the modified mini-van, with equipment that measured pollutants real-time.

Dr. Barbara Zielinska takes readings from the back of a mini-van, modified especially for the American Petroleum Institute project, to take samples over time.

Dr. Barbara Zielinska, Dr. Eric Fujita, Dr. John Sagebiel and Dave Campbell collaborated, with the help of DRI’s Larry Sheetz, to figure out the best way to sample air in 12 microenvironments having potential for higher pollutant exposures. A mini-van was modified to provide mobile air sampling for the in-cabin portions of the study. A motor home was equipped with analytical equipment so some samples could be analyzed in the field.

“The motor home was very useful because it served as a mobile office, analytical laboratory and meteorological station in one,” Fujita explained.

The study also included sampling air inside the vehicle cabin while trailing two separate vehicles with known lower and higher emission levels. How was this experiment done?

“We had a truck and car that previously had been tested in the laboratory in normal operating mode and with induced malfunctions so they would emit higher amounts of exhaust. We did the trailing vehicle study on an isolated country road away from traffic,” said Zeilinska. “Our objectives were to examine how in-cabin exposure levels vary with emission levels of the lead vehicle and proximity and speed of the two vehicles. We even sampled our own breath, breathing into special canisters.”

The results showed that the highest average exposure levels to benzene were observed during outdoor refueling and in the underground garage, owing to evaporative emissions and the cold start of the vehicle. The average exposure levels to 1,3-butadiene and formaldehyde were the highest in the underground garage followed by the roadway tunnel, toll plaza and surface parking lot.

What is MTBE?

MTBE (methyl tertiary-butyl ether) is a chemical compound manufactured by the reaction of methanol and isobutylene. It is produced in very large quantities almost exclusively for use as a fuel additive in motor gasoline. It is one of a group of chemicals known as “oxygenates” because it raises the oxygen content of gasoline.

Why is it being used?

Since 1979, MTBE has been used in U.S. gasoline at low levels to replace lead as an octane enhancer and help prevent the engine from “knocking.” Since 1992, it has been used at higher concentrations in some gasoline to meet the oxygenate requirements set by Congress in the 1990 Clean Air Act Amendments to reduce emissions of certain air pollutants. Due to concern about odor and water contamination, the use of MTBE is now being curtailed.