96: Lead

HISTORY AND EPIDEMIOLOGY

Industrial Applications

The low melting point and high malleability of lead made it one of the first metals smelted and used by humans. Ancient Egyptians and Hebrews used lead, and the Phoenicians established lead mines in Spain circa 2000 b.c. The Greeks and Romans released lead during the process of extracting silver from ore. Roman society found many uses for lead, including pipes, cooking utensils, and ceramic glazes, and a common practice was to use sapa, a grape syrup simmered down in lead vessels, as a sweetener and preservative.¹¹⁸ Post-industrial lead use increased dramatically, and today lead is the most widely used nonferrous metal, with global extraction on the order of 9 million tons annually.⁸² Lead is used widely for its waterproofing and electrical- and radiation-shielding properties. Use of both lead-based paint for house paint and leaded gasoline has been essentially eliminated by regulation in the United States since the 1980s, but is still a concern in many nations, and persistence of lead paint in older US homes still constitutes an enormous environmental challenge.³

History of Lead-Related Health Effects

Dioscorides, a Greek physician in the second century b.c., observed adverse cognitive effects, and Pliny cautioned the Romans of the danger of inhaled fumes from lead smelting.¹¹⁴ Modern authors have suggested that extensive use of sapa in Roman aristocratic society contributed to the downfall of Roman dominance.¹¹⁸ Lead poisoning was also recognized in American colonial times. Benjamin Franklin observed in 1763 the “dry gripes” (abdominal colic) and “dangles” (wristdrop) that afflicted tinkers, painters, and typesetters, as well as the “gripes” caused by rum distillation in leaden condensing coils.¹⁰⁵ Lead salts, particularly lead acetate (sugar of lead), were used medicinally in the early 19th century to control bleeding and diarrhea. With the 19th century Industrial Revolution, lead poisoning became a common occupational disease. The reproductive effects of lead poisoning were recognized by the turn of the 20th century, including the high rate of stillbirths, infertility, and abortions among women in the pottery industry or who were married to pottery workers.

The modern history of childhood plumbism can be traced to the recognition of lead-paint poisoning in Brisbane, Australia, in 1897.¹¹⁴ Lead poisoning was reported in American children in 1917, and by 1943, it was established that children who recovered from clinical plumbism were frequently left with neurologic sequelae and intellectual impairment. Symptomatic childhood lead poisoning was a frequent occurrence in American pediatric medical centers throughout the 1950s and 1960s, a period during which research established effective chelation therapy protocols with British anti-Lewisite (BAL) and edetate calcium disodium (CaNa₂EDTA).³⁴ From the 1970s to the present, the research thrust in childhood lead poisoning has centered on the recognition and quantification of more subtle neurocognitive impairment caused by subclinical lead poisoning.^16,115...