Tetraethyl lead (cont.)
Three decades later, the Surgeon General actually raised the lead standard to 4 cc/g (equivalent of 4.23 grams per gallon). This voluntary standard once again represented the outside range of industry practice. Nevertheless, the Surgeon General concluded in 1958 that a loosening of the voluntary standard posed no threat to the health of the average American: "During the past 11 years, during which the greatest expansion of tetraethyl lead has occurred, there has been no sign that the average individual in the U.S. has sustained any measurable increase in the concentration of lead in his blood or in the daily output of lead in his urine."
The actual industry average during the 1950s and the 1960s hovered in the vicinity of 2.4 grams per total gallon. The Department of Health, Education and Welfare (HEW), which was home to the Surgeon General starting with the Kennedy Administration, had authority over lead emissions under the Clean Air Act of 1963. The criteria mandated by this statute were still in the draft stage when the Act was reauthorized in 1970 and a new agency called EPA came into existence.
By then, the adverse effects of America's decades-old addiction to fossil fuel in general and leaded fuel in particular were becoming obvious to all. In 1971, the EPA's first Administrator, William D. Ruckelshaus, declared that "an extensive body of information exists which indicates that the addition of alkyl lead to gasoline...results in lead particles that pose a threat to public health."
It should be emphasized, however, that scientific evidence capable of documenting this conclusion did not exist in previous decades. Only very recently have scientists been able to prove that low-level lead exposure resulting from automobile emissions is harmful to human health in general, but especially to the health of children and pregnant women.
EPA took an emphatic stand on the issue in its final health document on the subject, "EPA's Position on the Health Implications of Airborne Lead," which was released on November 28, 1973. This study confirmed what preliminary studies had already suggested: namely, that lead from automobile exhaust was posing a direct threat to public health. Under the Clean Air Amendments of 1970, that conclusion left EPA with no option but to control the use of lead as a fuel additive known to "endanger the public health or welfare."
The very next month, in December 1973, EPA issued regulations calling for a gradual reduction in the lead content of the total gasoline pool, which includes all grades of gasoline. The restrictions were scheduled to be implemented starting on January 1, 1975, and to extend over a five-year period. The average lead content of the total gasoline pool of each refinery was to be reduced from the level of approximately 2.0 grams per total gallon that prevailed in 1973 to a maximum of 0.5 grams per total gallon after January 1, 1979. Litigation was to postpone implementation of this phasedown for two years.
Starting with the 1975 model year, US automakers responded to EPA's lead phasedown timetable by equipping new cars with pollution-reducing catalytic converters designed to run only on unleaded fuel. Fittingly, a key component of these catalysts that were to be the undoing of lead was that noblest of noble metals, platinum.
EPA estimates that ambient lead levels dropped 64 percent between 1975 and 1982.
In 1982, with the introduction of unleaded gasoline well underway, EPA developed a new standard intended to apply strictly to leaded gasoline.
On the basis of all that is known about the history of lead and its adverse effects on human health, it is impossible not to welcome EPA's lead phasedown initiative as well as the agency's decision to consider banning lead altogether from US gasoline.
Last Editorial Review: 6/9/2016
Back to MedTerms online medical dictionary A-Z List
Need help identifying pills and medications?