Medical Definition of Tetraethyl lead
Tetraethyl lead: An anti-knock compound added to motor fuel. Also known as tetraethylplumbane, tetraethyl lead has highly adverse effects on human health. It causes lead poisoning.
The History of Tetraethyl Lead
In 1921 three General Motors (GM) engineers -- Charles Kettering, Thomas Midgeley, and Thomas Boyd -- reported success with adding tetraethyl lead to improve engine performance and reduce engine knock. Through the Ethyl corporation, then a GM subsidiary, GM quickly began touting this lead compound as the virtual savior of the American automobile industry. The discovery was indeed extremely important. It paved the way for the development of the high-power, high-compression internal combustion engines.
The first danger sign was the mysterious illness that forced Thomas Midgeley to spend weeks convalescing in the winter of 1923. Midgeley had been experimenting rather recklessly with the various methods of manufacturing tetraethyl lead, and he did not at first realize just how dangerous the substance was in its concentrated liquid state. The deadliness of tetraethyl lead was sadly confirmed in the summer of 1924. Workers engaged in producing the additive fell sick and died at several refineries in New Jersey and Ohio. Banner headlines greeted each new fatality until a total of 15 workers had lost their minds and then their lives.
In 1925, the US Surgeon General temporarily suspended the production and sale of leaded gasoline. He appointed a panel of experts to investigate the recent fatalities that had "occurred in the manufacture and mixing of the concentrated tetraethyl lead." The panel was also asked to weigh "the possible danger" that might arise "from...wide distribution of a lead compound" through its sale as a gasoline additive.
Industry dominated the Surgeon General's investigatory committee, which included only one genuine environmental visionary, Dr. Alice Hamilton of Harvard University. The Coolidge Administration gave the panel just seven months to design, run, and analyze its tests. The committee's final report, published in June 1926, complained of the time constraints under which it had been forced to operate. Seven months was "not sufficient," argued the panel, "to produce detectable symptoms of lead poisoning" in experimental subjects because of the very slow gestation of that toxicological syndrome.
Nevertheless, the Surgeon General's panel ruled that there were "no good grounds for prohibiting the use of ethyl gasoline...as a motor fuel, provided that its distribution and use are controlled by proper regulations." The coming decades of Depression, total war, and post-war boom were hardly conducive to the implementation of "proper regulations" for leaded gasoline. Indeed, no compulsory standards were set for the industry until the early 1970s when EPA began its long, hard struggle to phase down lead levels in US gasoline.
One saturnine prophecy marred the otherwise sanguine 1926 report to the Surgeon General. By 1958 these words were to reverberate with particular resonance down the corridors of time: "It remains possible that, if the use of leaded gasolines becomes widespread, conditions may arise very different from those studied by us which would render its use more of a hazard than would appear to be the case from this investigation. Longer experience may show that even such slight storage of lead as was observed [among human guinea pigs] in these  studies may lead eventually to recognizable lead poisoning or to chronic degenerative diseases of a less obvious character. In view of such possibilities the committee feels that the investigation begun under their direction must not be allowed to lapse.... With the experience obtained and the exact methods now available, it should be possible to follow closely the outcome of a more extended use of this fuel and to determine whether or not it may constitute a menace to the health of the general public after prolonged use or under conditions not now foreseen.... The vast increase in the number of automobiles throughout the country makes the study of all such questions a matter of real importance from the standpoint of public health." Needless to say, this advice fell on deaf ears.
In 1927 the Surgeon General set a voluntary standard for the oil industry to follow in mixing tetraethyl lead with gasoline. This standard -- 3 cubic centimeters per gallon (cc/g) -- corresponded to the maximum then in use among refiners, and thus imposed no real restraint. Even without prodding, however, the industry did take giant strides toward instituting safer working conditions in oil refineries, thereby protecting individual laborers in the microcosm of the workplace.
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.Source: MedTerms™ Medical Dictionary
Last Editorial Review: 6/9/2016
Medical Dictionary Definitions A - Z
Search Medical Dictionary