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Lead's importance in myriad domestic and commercial applications is evident in the history of the names associated with them. Plumbers take their name from the Latin word for lead, plumbum, which also explains its symbol on the Periodic Table, 'Pb'. Decorators use a plumb line - literally a (formerly) lead weight on the end of a string - in order to accurately determine an angle 90 degrees to a theoretically level floor, and fishermen plumb the depths of their waters in order to determine where the bed is. And artists and manufacturers still refer to pencil graphite, whether in wood-case or mechanical pencils, as a lead. For a metal which was critical to everyday living, it is conspicuous by its absence; you're unlikely to come into contact with it during your day-to-day activities.
Leads position on the Periodic Table. (By Wiki contributor Sandbh, under CC BY-SA 4.0 license.)
Lead exists in different oxidation states, each one providing a different colour; these have been used throughout history in the manufacture of stable pigments for artists and industry. It's the stability of many toxic metals which is hard to replicate in safer, synthetic alternatives. Artists are familiar with lead carbonate in white oil paint, whilst car enthusiasts and mechanics will know red lead oxide, used as a primer for painting metal in cars. Slightly older generations will no doubt recall lead being banned from use in house paint. Over-painting simply presents the same dangers for future generations; paint dust and flakes, generated during the removal of older layers, is inhaled, and the decades-old lead affects a new generation.
Some artistic paint manufacturers still produce quantities of lead-based pigments, such as the cremnitz white available from the superb Michael Harding's oil range. It is only available in sealed cylinders, and fairly large ones at that, presumably to ensure that it is only purchased by those artists who know what they're doing.
Paint made with lead carbonate is characteristically heavy. Here, our man demonstrates this property, using Michael Harding's 'cremnitz white'. (Copyright © Granthams Ltd.)
Lead has been poisoning people for as long as people have been coming into contact with it. Successful smelting and widespread industrial applications have seen to that; its usefulness in transporting water has helped bring water - and lead contamination - to rich and poor people alike. In fact, it's more than a great leveller, since rich Romans used lead(II) acetate or, to give it its less sinister name, 'sugar of lead', as a sweetener. Another nickname is salt of Saturn. Whatever they called it, it the effects were the same: abdominal pain, headaches, seizures and death. It has even been implicated in the collapse of the Roman Empire, owing to its use by the Imperial families. Fancy names: clever marketing for a deadly chemical. Geisha used lead-based white makeup, before lead's toxicity was properly understood, and an alternative pigment sourced. 18th Century royalty, courtesans and politicians painted their faces with white and red lead make-up, in some instances using the white version to whiten their eyes. Needless to say, they were aware of the effects of overuse. The lesser effects were probably confused with everything else that was going wrong with them.
Examples of lead. (Copyright © Alchemist-hp. Shared under Free Art License 1.3)
Probably its most recent widespread use, i.e., in all communities and at all societal levels, was as an additive in petrol. Lead was finally removed from UK petrol only in 1998. Lead is most effectively absorbed across a moist membrane, such as across the lining of the mouth, throat, lungs and gut. Burning petrol and then pumping the exhaust gases into the air, whether in town centres or the countryside, is an effective way of distributing lead particulates and getting them into people's eyes and lungs.The problem for humans and many other animals is that lead is easily absorbed, particularly when we've turned into powders and liquids. It can also be absorbed through meats and vegetable that have already absorbed it, i.e., if those animals and plants were already poisoned by lead. This is known as organic lead, and is more dangerous as it more readily taken up by biological processes.
It can accumulate over time, distributing itself in the body in preference to the regular, beneficial chemicals, causing gradual failure of biological systems, or it can be absorbed in a sudden hit, producing a kind of chemical shock. When cells manufacture proteins, lead replaces the correct metals, distorting the proteins and rendering them useless. In the brain, lead replaces the calcium ions so necessary for generating impulses, causing diminished recall. It's bad enough in adults, but it's a major concern in children's development, as this is a period of increased growth and specialisation. Exposure at this point can result in deformities and defects which likely won't repair. Since lead isn't used in human biological processes, there is no safe level, just avoidance.
Front page image by Wikipedia contributor Sb2s3, used under CC BY-SA 4.0 licence.
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