Lead is among the most revered and the most maligned of elements. Historically its beneficent properties have made it hard to resist, though its virulence is the stuff of legend. Lead was added to cosmetics and eye salves in predynastic Egypt, and prescribed as a cure for fever, rash, indigestion, and lust in ancient Rome. The Roman naturalist Pliny the Elder cautioned that "all the current instructions on the subject of [lead's] employment for medicinal purposes are in my opinion decidedly risky." But his warning went largely unheeded by the Roman nobility, whose habit of drinking potions sweetened with "sugar of lead" is said to have hastened the toppling of their empire.
Lead acquired new uses in the industrial age with the mass manufacture of lead solder, lead pipe, and lead-tinted pigments for glazes and paints. The mineral's high density made it a natural to be used for bullets and shot, and its malleability rendered it an ideal material for type--in which context it came to the attention of Benjamin Franklin. Citing his own "lead colic," brought on by frequent encounters with the printing press, Franklin wrote, "The mischievous Effect from lead is at least above Sixty Years old; and you will observe with Concern how long a useful truth may be known, and exist, before it is generally received and practis'd on."
Franklin was right on the mark. Although some of lead's applications waned with reports of its toxicity (for example, the French banned the manufacture of leaded white pigments in the mid-1800s for fear of poisoning craftsmen), new uses for the mineral continued to pop up well into the twentieth century: lead tubes for toothpaste, lead sheathing for electrical wire, lead shields for x-ray machines, lead plates for batteries, and lead and more lead in paint smeared on everything from boat bottoms to baby carriages. By the early 1930s severe lead poisoning, characterized by convulsions, coma, brain damage, and death, was recognized as a fairly common disease of childhood. The paint industry began voluntarily to reduce the amount of lead in its products in the following decade, but the discovery of tetra-ethyl lead as an anti-knock additive for gasoline increased lead mining worldwide. Sales of leaded gasoline rose steadily through the 1960s, with a resulting dispersion into the environment of millions of tons of lead from car exhaust. Meanwhile, more than 150 clinics were set up nationwide to deal with a steady stream of lead-poisoning cases. Like the Romans, it seemed, we had entered into a devil's wager with lead, using the public health as our stake.
All that, of course, has changed. Over the past quarter century Americans not only have kicked the lead habit but have turned on lead with the zeal of the betrayed. Congress banned lead-based paint for residential use in 1978, and by 1990 the amount of lead in gasoline had dropped 99.8 percent from mid-1970s levels. Also in 1990 cans with lead seams, no longer manufactured in this country, constituted less than one percent of the market; copper or plastic pipes, not lead ones, were standard in plumbing; lead solder had been banned; and lead smelters and industries that used lead had been forced to limit their emissions sharply. Blood-lead levels, measured in micrograms of lead per deciliter of blood, dropped accordingly. In July of last year the results of the first phase of the third National Health and Nutrition Examination Survey, published in the Journal of the American Medical Association, indicated that average blood-lead levels had plummeted. Pockets of lead poisoning remained, mostly in the inner city, but generally the numbers were cheering: the survey concluded that only one half of one percent of children who were tested had blood-lead levels exceeding the "intervention level" set in 1985 by the Centers for Disease Control and Prevention.
This triumph over lead is widely touted as one of the great public-health success stories of the century, a stunning example of the strength of activism over vested interests. But many are unwilling to declare victory. The Environmental Protection Agency and the Department of Health and Human Services say that lead poisoning continues to be the No. 1 "environmental disease of children, affecting at least ten percent of all preschoolers." The CDC calls lead poisoning the "most common and societally devastating environmental disease of young children." And an influential Washington lobby, the Alliance to End Childhood Lead Poisoning, states as "inescapable fact" that "approximately ten percent of all U.S. preschoolers are lead-poisoned, eclipsing other environmental health hazards and preventable childhood diseases." Other groups and the media have picked up the chant, citing widespread low-level lead poisoning as the trigger for ills ranging from attention-deficit disorder to juvenile violence.
Despite the impressive roster of medical and scientific organizations supporting these claims, however, the characterization of lead poisoning as a "silent epidemic" is not a scientific truth but a rhetorical pose. Symptomatic lead exposure that causes clear clinical effects of mental or physical impairment is exceedingly rare. Even moderate blood-lead elevations, at the CDC's 1985 intervention level, are also quite uncommon. To get to the "one out of ten preschoolers" figure, regulatory agencies now deem as "poisoned" children whose lead-to-blood ratios fall between 10 and 25 micrograms per deciliter --considered within the acceptable range five years ago. (Children in the early 1960s averaged more than 20 micrograms.) With the stroke of a pen in 1991 the CDC changed "lead poisoning" from a clear diagnosis to a murky condition, thereby enlarging eighteenfold the likely population at risk and encouraging the enactment of sweeping anti-lead legislation. Sanford Weiner, a specialist in risk assessment at the Center for International Studies at the Massachusetts Institute of Technology, puts it this way: "The agencies moved the goalposts."