30. Lead Poisoning (plumbism)

Summary

Lead is a dense elemental metal utilized by humans for possibly over 8,500 years. This toxic material has no known biological function in human physiology. It is particularly harmful to the brain, peripheral nervous system, blood, gastrointestinal tract, reproductive organs, mental health, and essentially every other major organ system.

Morbidity and Mortality

At very high exposure levels (usually > 100 ug/dL BLL), lead can cause seizures, coma, and death via cerebral edema. However low levels of lead exposure (> 5 ug/dL BLL) over time are really the bigger concern. Even low levels of lead have been shown to lower IQ and cause behavioral disturbances. 815 million children worldwide are believed to have dangerously high lead levels, 500,000 a which reside in the United States. An estimated 900,000 adults are killed every year from lead poisoning. Worldwide, lead may account for as much as 1% of the global burden of disease.

Story Time

Roman aristocratic society made a sweetener called sapa, a grape syrup simmered in lead containers. Many historians believe that extensive use of sapa, reduced the IQ of the ruling class, likely contributing to the fall of the empire. Before 1976 and 1978, lead was routinely added to gasoline and household paint in the United States. Blood lead levels (BLL) decreased from 12.8 ug/dL to 0.82 ug/dL over the 35 years following federal regulations banning lead additives in individuals age 1 to 74 years. This likely resulted in the average IQ increasing between 7 and 12 points. 

Key Points

1. Children are at greatest risk for lead toxicity as they tend to put things in their mouth. Old houses with chipping lead paint are the greatest risk factor. Though blood lead levels have declined dramatically, the CDC and AAP still recommend routine screening in children.

2. Occupational exposures are the greatest risk factor for lead poisoning in adults. Lead smelters, constructions workers, automotive radiator repairmen, firing range instructions, battery manufacturers, lead abatement workers, and metal workers are at greatest risk.

3. The CDC has steadily decreased their definition of elevated blood levels from < 60 ug/dL to < 5 ug/dL over the past 60 years. There is no safe lead level.

4. Blood lead levels are currently the best screening and diagnostic test for lead poisoning. Most lead is absorbed into the bone and can leach out into the body over decades. In the future, we will likely judge cumulative exposure by looking at bone lead levels.

5. Removing the lead exposure is the most important treatment. At BLL > 45 in children and > 70 in adults, chelation therapy with substances like dimercaptal, CaNa2 EDTA, and succimer are both recommended and efficacious.

References

-       Calello and Henretig. Ch. 93. Lead. Goldfranks Toxicology, 11th Ed. 2019

-       Burki. Report says 815 million children have high blood lead levels. Lancet. 2020.

-       Dignam, Kaufmann, LeStourgeon, & Brown. Control of Lead Sources in the United States, 1970-2017: Public Health Progress and Current Challenges to Eliminating Lead Exposure. Journal of public health management and practice. 2019.

-       Wikipedia: Lead, lead poisoning

-       WHO. Lead, Assessing the Environmental Burden of Disease. Available at: https://www.who.int/quantifying_ehimpacts/publications/9241546107/en/#:~:text=It%20is%20estimated%20that%20lead,exposure%20to%20lead%20is%20required.

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