Wednesday, March 5, 2014

Scientific Exploits of Ben Franklin Part 4: Lead Poisoning

Franklin, ca. 1783
I want to continue my long-standing series on the scientific and medical contributions of Benjamin Franklin, not only because I find him to be a fascinating man, but also because as much as we revere him for his more popular scientific discoveries and inventions (electricity, bifocals, etc.), he made many other important contributions that few people are aware of.  Most people probably have no idea that Ben played an important role in the recognition of lead poisoning by medical doctors in colonial America and Europe, a fact that improved and saved many lives.

Humans started mining and using the metal lead over 6 thousand years ago.  Lead was tremendously useful in large part because it is resistant to corrosion and is highly malleable and easy to work with.  Lead was often heated and melted so that the molten lead could be poured into forms to create braces to hold other wooden or stone structures together.  The Romans first made water pipes out of lead, and for the next several thousand years, people were mining and using lead and lead-based products, all the while frequently poisoning themselves.  Pretty crazy to think about, isn't it?  Let's talk for a moment about lead poisoning in human history and the role of Benjamin Franklin in recognizing the self-destructive human over-use of lead.

Lead pipe in Roman Baths (©Ad Meskens/Wikimedia Commons)
In addition to being a very useful metal, lead is also a potent neurotoxin that, when ingested or inhaled, can be rapidly absorbed and accumulate in soft tissues and bones of the body.  Lead damages nerves that leads to muscle weakness, pain, confusion, or even seizures.  Lead salts can also lead to anemia, immune system disfunction, and kidney toxicity.  Animals and plants can also suffer from the toxicity of lead.  Lead poisoning is not limited to humans.

There is no safe threshold for lead toxicity.  That means that there is no known "safe dose" of lead exposure that won't cause some harm to the body.  This is the reason that lead based paints are such a hazard to children and pets.  As these paints age and flake or crumble into dust, ingesting them is very dangerous.

Cube of lead (from C. Niehaus/Wikimedia Commons)
Ancient historical documents tell us that the link between lead and poisoning was discovered and then subsequently forgotten several times in human history.  The Greek physician-scientists Hippocrates and Nicander likely described lead poisoning in 3rd and 2nd centuries B.C.E., respectively, but they didn't actually figure out that the cause was lead.  One of Julius Caesar's aqueduct engineers, Vitruvius, recognized that water from clay pipes was healthier than water coming from lead pipes, which seemed to "be made injurious by lead."

However, while Roman lead poisoning was a big problem, it has been speculated that the epidemic could have been much worse.  For the most part, calcium carbonate deposits forming inside the lead pipes of the aqueducts likely insulated much of the water in the pipes from actually touching the lead.  Many of the lead poisoning cases among the Romans may have come from the salt lead II acetate (Pb(C2H3O2)2), a sweetener used in wine as well as in cosmetics along with another lead compound called white lead (2PB(CO3)·PB(OH)2).  It wasn't until the 17th century that the German physician Eberhard Gockel recognized the toxicity of lead salts used in wine.  These were eventually outlawed, but still used illegally for many more years.          

In the early to mid 1700s, a disease was plaguing Europe and the American colonies called the "dry-gripes" or "dry-bellyache."  Unknown to many people at the time, this was lead poisoning.  At this time, lead was used in lots of materials that came into contact with foods and beverages, including the cooling coils of stills that were used to distill alcoholic beverages like rum.  Much of the rum drank by the colonists was actually contaminated with lead from these stills.  Physicians in Massachusetts eventually recognized this and passed a law prohibiting the use of lead in distillation equipment in 1723, which drastically reduced the cases of lead poisoning in New England.  However, lead use in the colonies and Europe was still rampant.      

Franklin at his desk
Franklin wrote about his childhood memories of this Boston incident in a famous letter to his friend, Benjamin Vaughan (full text available here):

I remember of this kind, was a general discourse in Boston when I was a Boy, of a Complaint from North Carolina against New England Rum, that it poison'd their People, giving them the Dry Bellyach, with a Loss of the Use of their Limbs. The Distilleries being examin'd on the Occasion, it was found that several of them used leaden Still-heads and Worms, and the Physicians were of the Opinion that the Mischief was occasion'd by that Use of Lead....

Franklin's opinion about lead were also shaped by his experiences as a printer, originally working for his brother in Boston but then setting up a successful printing and publishing business of his own after he moved to Philadelphia in 1723.  He opened a print shop in 1728, began printing the Pennsylvania Gazette newspaper in 1729, and started publishing Poor Richard's Almanack in 1730.  Franklin wrote about this experience and his own personal experiences with the lead blocks used at that time to set type:

In 1724, being in London, I went to work in the Printing-House of Mr. Palmer, Bartholomew Close as a Compositor. I there found a Practice I had never seen before, of drying a Case of Types, (which are wet in Distribution) by placing it sloping before the Fire. I found this had the additional Advantage, when the Types were not only dry'd but heated, of being comfortable to the Hands working over them in cold weather. I therefore sometimes heated my Case when the Types did not want drying. But an old Workman observing it, advis'd me not to do so, telling me I might lose the Use of my Hands by it, as two of our Companions had nearly done, one of whom that us'd to earn his Guinea a Week could not then make more than ten Shillings and the other, who had the Dangles, but Seven & sixpense. This, with a kind of obscure Pain that I had sometimes felt as it were in the Bones of my Hand when working over the Types made very hot, induc'd me to omit the Practice. But talking afterwards with Mr. James, a Letter-founder in the same Close, and asking him if his People,who work'd over the little Furnaces of melted Metal, were not subject to that Disorder; he made light of any Danger from the Effluvia, but ascrib'd it to Particles of the Metal swallow'd with their Food by slovenly Workmen, who went to their Meals after handling the Metal, without well-washing their Fingers, so that some of the metalline Particles were taken off by their Bread and eaten with it. This appear'd to have some Reason in it. But the Pain I had experienc'd made me still afraid of those Effluvia.

Many of Franklin's thoughts about lead poisoning are outlined in his correspondence letters with  Philadelphia physician Cadwalader Evans and friend Benjamin Vaughan.  He repeatedly recognized and described how symptoms that characterized the "dry-bellyache" were often correlated with lead exposure.  Beyond his observations of contaminated rum and the printing industry, Franklin noted that mosses did not grow on rooftops or eaves that were that were painted with the white lead-based paint used at the time, and he also noted that he directly observed a family who contracted the "dry-bellache" after drinking water that they collected from such a roof painted with lead paint.   In his letter to Vaughan, he wrote about this:

Franklin at his desk
In America I have often observed that on the Roofs of our shingled Houses where Moss is apt to grow in northern Exposures, if there be any thing on the Roof painted with white lead, such as Balusters, or Frames of dormant Windows, and there is constantly a streak on the Shingles from such Paint down to the Eaves, on which no Moss will grow, but the Wood remains constantly clean and free from it.--We seldom drink Rain Water that falls on our Houses; and if we did, perhaps the small Quantity of Lead descending from such Paint, might not be sufficient to produce any sensible ill Effect on our Bodies. But I have of a Case in Europe, I forgot the Place, where a whole Family was afflicted with what we call the Dry-Bellyach, or Colica Pictonum, by drinking Rain Water. It was at a Country Seat, which being situated too high to have the Advantage of a Well, was supply'd with Water from a Tank which receiv'd the Water from the leaded Roofs. This had been drank several Years without Mischief; but some young Trees planted near the House, growing up above the Roof, and shedding their Leaves upon it, it was suppos'd that an Acid in those Leaves had corroded the Lead they cover'd, and furnish'd the Water of that Year with its baneful Particles and Qualities.

Franklin, ca. 1746
When Franklin spent time in Paris in 1767, he visited La Charite hospital, which cared for many patients who had "dry-bellache" symptoms. Franklin noted that all of the patients had occupations that somehow involved exposure to lead.  He wrote:

When I was in Paris with Sir John Pringle in 1767, he visited La Charite, a Hospital particularly famous for the Cure of that Malady, and brought from thence a Pamphlet, containing a List of the Names of Persons, specifying their Professions or Trades, who had been cured there. I had the Curiosity to examine that List, and found that all the Patients were of Trades that some way or other use or work in Lead; such as Plumbers, Glasiers, Painters, and excepting only two kinds, Stonecutters and Soldiers. These I could not reconcile to my Notion that Lead was the Cause of that Disorder. But on my mentioning this Difficulty to a Physician of that Hospital, he inform'd me that the Stonecutters are continually using melted Lead to fix the Ends of Iron Balustrades in Stone; and that the Soldiers had been emply'd by Painters as Labourers in Grinding of Colours.

George Baker (1722-1809)
Franklin also corresponded with another physician, George Baker, and described his observations about lead poisoning.  Baker was spurred on by Franklin's idea to look more closely at a disease that was affecting the people of Baker's hometown of Devonshire (now Devon), England.  This disease was called the "Devonshire Colic," and its symptoms included weight loss, muscle weakness, and confusion.  Baker's discussions with Franklin lead Baker to realize that the cause of the Devonshire Colic was likely lead-contamination, perhaps from apple cider that was popular in Devonshire.  Baker discovered that the apples for the cider were being crushed in a mill that had mill wheels built with wooden boards held together with poured lead braces.  Thanks to Baker's discussions with Franklin, Baker discovered the cause of the Devonshire Colic and, despite significant opposition from the cider industry that they were the cause of the contamination, Baker's discovery eventually and new manufacturing processes led to the disappearance of the disease.

Unfortunately, despite the progress made by Franklin and other 18th century scientists and physicians,  the idea of lead toxicity and its full impact was not completely realized until the 20th century.  People did not understand just how toxic lead actually is.  Lead paints were cheap and used commonly up until the early 1900s in Europe.  Lead paint was banned worldwide by the League of Nations (a precursor to the UN) in 1922, but the US did not actually pass a law banning the use of lead paints until the 1970s.  Today, modern medicine recognizes that even low-level lead exposure carries health risks.  Most people are aware of the dangers of the inhalation or ingestion of lead paint chips or dust, but it is always fascinating to me how something that we take for granted, like the toxicity of lead, was such a hard-fought realization to come to.

At the time Franklin wrote his letter to Benjamin Vaughan about lead poisoning, Franklin thought that the idea of lead poisoning had only been around for about sixty years, since the episode of contaminated rum in Boston.  He was unaware that the idea actually went back well over a thousand years.  Even so, Franklin thought it was truly scary that the observations and ideas of lead poisoning had been around 60 years and yet it still wasn't fully accepted.  Franklin remarked that his friend Vaughan that he "will observe with Concern how long a useful Truth may be known, and exist, before it is generally receiv'd and practis'd on."

Those are scary but very true words.  As usual, Franklin's wisdom  transcends time.  While modern medicine now accepts and understands lead poisoning, unfortunately not much has changed in terms of human attitudes and behavior in the past couple of hundred years.  I worry very much that someday in the not-to-distant future we'll take a look back climate change and be shocked by a very similar lack of acceptance and action.

Text © 2014, TheMadScienceBlog.  Images are public domain unless otherwise indicated.  

Sources and Further Reading
  • D.C. Bellinger and A.M. Bellinger.  "Childhood Lead Poisoning: The Torturous Path from Science to Policy."  Journal of Clinical Investigation.  2006.  116:853-857.  Available here
  • L. Gensel.  "The Medican World of Benjamine Franklin."  Journal of the Royal Society of Medicine.  2005.  98:534-538.  Available here.
  • S. Hernberg.  "Lead Poisoning in a Historical Perspective."  American Journal of Industrial Medicine.  2000.  38:244-254.  
  • J.V. Hirschmann.  "Benjamin Franklin and Medicine."  Annals of Internal Medicine.  2005.  143:830-834.
  • A. Hodge.  Roman Aqueducts and Water Supply.  London: Duckworth.  1992.  ISBN 0-7156-2194-7.  
  • E.J. Huth.  "Benjamin Franklin's Place in the History of Medicine."  Journal of the Royal College of Physicians of Edinburgh.  2007.  37:373-378.
  • M.A. Riva, et al.  "Lead Poisoining: Historical Aspects of a Paradigmatic and Environmental Disease."  Safety and Health at Work.  2012.  3:11-16.  Available here.  


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