The EPA Encourages Move Toward Unleaded Fuel

Feature examines the reasoning and consequences behind the Environmental Protection Agency's decision in the 1980s to phase out the lead-based gasoline fueled automobile.


| January/February 1986



Gas Pump

The EPA took steps to crack down on the use of lead in fuel in the 1980s.


PHOTO: FOTOLIA/TIMURD

Lead. It's a word you'll probably be hearing a lot over the next few years, because the Environmental Protection Agency (EPA) has launched a major campaign to ban its use in all gasoline motor fuels. But before that federal agency is successful in its effort, you might want to be aware of some facts that could affect you more directly than you might think.

Technically speaking, the "lead" in question is tetraethyl lead (TEL), a toxic, oily compound developed in 1922 as an antiknock additive. At that time, before petroleum refining processes were perfected, the addition of lead increased gasoline's octane rating — its measure of resistance to harmful detonation — from somewhere around 50 to about 75. Modern gasoline, prior to the introduction of lead, has an average octane number in the mid-80s; adding just a teaspoonful of TEL to every gallon raises that figure by about six points, enough to satisfy the needs of nearly all automobile engines.

Unfortunately, the unchecked use of lead in motor fuel has taken its toll by contributing to gas pollution. In part, the steady development of efficient, high-compression engines in the two decades from the early 1950s to 1970 reflected the proportional increase in the amount of TEL used during that period. More significantly, the explosive growth in the world's use of automobiles since World War II from just over 50 million vehicles in 1950 to well over 300 million today — has played a major role in the poisoning of our environment.

The fact that high levels of lead contamination have an adverse effect on human health has never been questioned. But more recent evidence suggests that levels of lead concentration in the blood lower than that previously thought dangerous may have some effects as well. Additionally, studies conducted by the EPA and several other institutions show a direct correlation between the total amount of lead used in gasoline and the blood-lead levels of both children and adults.

Lead exposure is measured in micrograms per deciliter of blood (pg/dl); the CDC recently lowered its definition of lead toxicity from a blood-lead level of 30 µg/dl to one of 25 µg/dl. Even so, a number of effects have been -detected at blood-lead levels as low as 10 to 15 µg/dl. These include a restriction in the synthesis of heme (an element critical to the formation of hemoglobin and certain detoxifying liver enzymes), a change in brainwave patterns, and an inhibition of vitamin D metabolism (which is necessary to the normal growth and development of children).

Equally incriminating is the relationship between lead use in fuel and lead concentration in humans: Between 1976 and 1980, the amount of TEL used in gasoline production dropped from just over 100 thousand tons per six months to a low of about 48,000 tons per half-year. In that four-year period, average bloodlead levels declined at a similar rate, from 16 µg/dl to 9.6; more significantly, the trends followed each other closely and even matched seasonal fluctuations. Currently, the EPA maintains that leaded gasoline is responsible for 80 percent to 90 percent of all airborne lead emissions. If that figure is accurate, motor fuel accounts for more than half a child's, and about one-third of an adult's "baseline" exposure to lead, which is a term used to indicate the level encountered in a typical rural area, removed from the urban sources of lead pollution.





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