Found naturally in the Earth’s crust, it’s known for its high density and low melting point, and its resistance to corrosion and moisture. In ancient Roman times it was used in the production of chastity belts and cups, plates and pitchers. But then the Roman elite became aware of its toxicity, and believed it caused madness and death among the slaves who handled it most often. But that didn’t stop it from being used more recently in this country in the production of gasoline, paint, and piping for homes and businesses. It, of course, is lead and its potential adverse health effects on the body – particularly the kidney – the topic of pediatric nephrologist Jeffrey Fadrowski’s Grand Rounds presentation.
“Lead exposure is a well-established risk factor for neurological damage and developmental delays in children,” Fadrowski said, “and chronic exposure to high lead levels is a well-known cause of chronic kidney disease in adults.”
Chronicling its evolution as a health hazard, Fadrowski noted that Australian physician J. Lockhart Gibson in 1905 was among the first to describe lead poisoning among children in contemporary times. In this country it was physicians Henry Thomas and Kenneth Blackfan, the latter from Johns Hopkins Department of Pediatrics, who in 1914 who detailed the case of a boy from Baltimore who died of lead poisoning after ingesting white lead paint from the railing of his crib. They described patients with lead poisoning as “fretful, peevish, and often very restless at night. Their appetite was poor and their gums began to bleed, and soon pain shot up and down their legs. Their stomachs began to ache and they became constipated.” In 1956, J. Julian Chisolm and Harold Harrison were the first to formally study how a child’s environment contributed to lead exposure, noting that the only protective measure is the removal of lead from the child’s environment. But that took some time.
Despite accumulating evidence of lead’s harmful effects in medical journals, it wasn’t until 1973 that the U.S. government called for the gradual reduction of lead in gasoline, and not until 1978 did it ban lead from paint. Lead, derived from the Latin word plumbum—which led to the name “plumber” for the worker of pipes—wasn’t regulated in the water supply until 1991. Did these actions solve the problem of lead exposure? Even though lead levels significantly declined—and continue to decline today—Fadrowski noted, “The simple answer is ‘no.’”
Citing a 2009 Pediatrics study that looked at lead levels over a 15-year period beginning in 1988, Fadrowski reported that the majority of the U.S. population still has detectable lead levels. Lead-based paint is still a problem and probably the most common source of lead exposure, with an estimated 3 million tons of lead remaining in U.S. homes built before 1980. Lead is in the soil, too. “If you don’t believe that, ask the Obamas,” said Fadrowski, noting that elevated lead levels were found in the White House garden.
So, is lead a heavy metal with weighty health effects? What are lead’s harmful documented effects? How do we measure lead in the body, and what’s a safe level? What’s the threshold for public health intervention?
There’s little or no controversy regarding the toxic effects of high levels of lead on the kidney, said Fadrowski, citing a well-known epidemic of lead poisoning in Queensland, Australia in the early 1900s. The exposure came from lead paint on verandas—a favorite play place for children—that flaked into powder under the hot sun. Two to three decades later, a group of Australian physicians noticed a huge increase in the incidence of chronic kidney disease, which was attributed to previous lead poisoning.
Cases of lead and nephrotoxicity, some famous, date back even earlier. A strand of hair taken from Andrew Jackson, president of the United States from 1829 to 1837, indicated lead levels consistent with lead poisoning. A fan of the “sugar of lead” remedy for gastrointestinal problems, Jackson regularly bathed in the substance. Harboring two lead bullets left by gun duels didn’t help either. Jackson exhibited many symptoms and signs compatible with lead poisoning, including rapid tooth loss, colic, diarrhea, pallor, hand tremor, irritability, paranoia, violent mood swings, and it is thought that he likely died from chronic kidney failure (JAMA, 1999;282:569-571).
Multiple other studies over the years, Fadrowski noted, have demonstrated progressive kidney toxicity associated with lead exposure, which is most typically measured in the body by micrograms of lead per deciliter of blood. In 1991, the Centers for Disease Control and Prevention (CDC) reduced the lead “level of concern” for children from 25 micrograms to 10 micrograms per deciliter of blood. But a recent Hopkins Children’s study suggests that even levels below 10 may pose a risk to kidney function (Archives of Internal Medicine, Jan. 11, 2010). Although more than 99 percent of the 769 healthy children and teens in the study had lead levels below 10, those with lead levels in the upper quarter of the range had lower kidney function compared to those with the lowest lead levels. Measuring their kidney function through both the traditional creatinine test, and a newer, more-accurate test that measures how fast the kidneys filter out the protein cystatin C, Fadrowski and fellow researchers found more pronounced differences in kidney function using the cystatin C test. Past studies using creatinine, Fadrowski noted, may have underestimated the true effect of lead on kidney function.
The health effects of lower levels of lead, representative of current exposures, Fadrowski concluded, will continue to be studied, and based on this research the CDC will continue to evaluate the level of concern—the threshold to initiate public health intervention.
“Even though lead levels are declining, lead exposure remains an issue for children and, thus, pediatricians,” Fadrowski said. “Pediatricians should continue to screen lead levels as recommended by the CDC, and help make families aware of increased risks for lead exposure based on housing characteristics, remodeling of homes, and certain hobbies and occupations.”