Lead and the decline of empires

The Ancient Greek poet and physician Nicander described the symptoms of lead poisoning, including hallucinations and paralysis, and recommended strong laxative treatments to cure it. Yet lead continued to poison unchecked, largely because the link between the metal and its adverse effects on health was not obvious. On the other hand its benefits were obvious, indeed the more lead was used in a society, the higher the standard of living of its citizens. Lead can be an extremely useful metal because it is easy to win it from its ores, it melts at a relatively low temperature, and it makes an ideal solder. Lead is easily worked and can be hammered into sheets, and used to make pipes, pans, roofing, and cisterns, and it is impervious to attack by the oxygen of the air and by water.

Lead has been mined for more than 6000 years, and it was certainly known to the Ancient Egyptians who used lead pigments as well as casting the metal itself into small figurines. Cosmetics made from lead ores have been found in tombs of the second millennium bc, and these consisted of black galena (lead sulphide), white cerussite (lead carbonate), white lauri-onite (lead chloride), and brown phosgenite (mixed lead chloride carbonate).

The Egyptians may have got some of their lead from Phoenician traders who were mining lead in Spain about 2000 bc, but it was the ancient Greeks who really began producing lead on a large scale, inadvertently as it happened, because they were really mining for silver. From 650 to 350 bc the Athenians exploited a large deposit at Laurion from which they eventually extracted 7000 tonnes of silver - and more than 2 million tonnes of lead.

The silver from Laurion underpinned Athens' economic power, until the mines became played out in the fourth century bc, after which Athens declined. By then more than 2000 pits had been dug and 150 km of galleries excavated. The waste lead from these mines was still being exploited hundreds of years later by the Romans, who found more and more uses for the metal and its compounds. Builders, plumbers, painters, cooks, potters, metal-workers, coin-makers, dentists,* vintners, and undertakers all made use of it. (Lead coffins were used extensively throughout the Roman period to bury important individuals.)

The Ancients saw lead as a god-given benefit and in Egypt it was associated with the god Osiris, while the Greeks linked it to Chronos, and the Romans to Saturn, which is why lead poisoning is still sometimes called saturnism. In reality lead was really a metal sent from hell. A puzzling feature of the Roman Empire was the surprisingly low birth rate of its ruling classes, and this too has been linked to the high level of lead in the diet. If the fate of a ruling class is what determines the fate of an empire, then the theory that one of the greatest of all empires was destroyed by lead may not be so fanciful as it first sounds. In fact more than just the aristocracy appears to have been less than reproductive. The Empire's population remained stable at around 50 million, despite such social benefits as adequate food supply, high standards of hygiene, and the growth of science, technology, and medicine, all of which should have led to an increase.

Some researchers have put forward the theory that lead was to blame, and we know from the analysis of the bones of its citizens, that their use of this metal was undermining their health. The theory that lead led to the decline of the Roman Empire was first advanced in 1965 in the Journal of Occupational Medicine by S. C. Gilfillan of Santa Monica, California, and his

* The ancient Romans used lead fillings for teeth.

arguments were subsequently reinforced by Jerome Nriagu of the National Water Research Institute of Canada. Nriagu, writing in the New England Journal of Medicine (Vol. 308, p. 660, 1983), estimated that a typical aristocrat would be absorbing 250 ^g/day, while ordinary Roman citizens would get around 35 and slaves only 15, most of which would come from wine in the case of the first two groups. Nriagu has even linked the medical complaints and bizarre behaviour of the Roman emperors to their high lead intake. Many of them suffered from gout as a result. Claudius who reigned from 41 to 54 displayed many of the symptoms of lead poisoning, including recurrent attacks of colic. Nriagu expanded on the theory in a scholarly but controversial book, Lead and Lead Poisoning in Antiquity, published in 1983.

Lead contaminated the homes of Romans in many different ways. Drinking water was transported along lead-lined aqueducts, through lead pipes, stored in lead cisterns, and maybe drunk from lead pewter vessels. The walls and woodwork of rooms were painted with lead-based paints. But one item in particular must have contributed to the lead in their diet, and that was a sweetening agent known as sapa. The famous Roman writer Pliny (23-79) gives the recipe for making sapa and specifically mentions that it must be made in lead pans.

Roman cooks had only two sweetening agents that they could use for desserts: honey and sapa.* Sapa was made by boiling down unwanted or sour wine in lead pans and we now know that the syrup so produced tasted sweet because it contained a lot of lead acetate. The lead came from the pan in which it was prepared, the acetate came from the wine that was being made sour by the action of enzymes and air which can convert alcohol to acetic acid. The crystals that form from such syrup looked and tasted like the sugar we know today, and were eventually to be known as sugar of lead. Old recipes for making sapa have been repeated in recent times, and analysed, showing that the syrup contained around 1000 ppm of lead (0.1%). A spoonful of sapa would deliver a dose of lead that would undoubtedly lead to some of the symptoms of poisoning. Yet the popular Roman book, The Apician Cookbook, had sapa as an ingredient in 85 of its 450 recipes, and sapa was used by vintners as well.

* Sugar was unknown to the Romans. Sugar cane was originally to be found only in Polynesia, and gradually spread westwards reaching Europe about 800.

Sapa was used to preserve wine, and especially Greek wines. These were popular in Rome but had a reputation for causing sterility, miscarriages, constipation, headaches, and insomnia - all of which would be true if they had been doctored with sapa. Roman prostitutes were reputed to eat sapa by the spoonful because it acted as a contraceptive, gave them attractive pale complexions (due to anaemia), and would cause abortions.

The Romans mined lead in Greece, Spain, Britain, and Sardinia. At the height of the Empire the British deposits were the main source of supply and the annual rate of lead production was in excess of 100000 tonnes/year. (In total, the Romans are estimated to have mined and used more than 20 million tonnes of lead.) Originally the Romans left the mining and refining in private hands, but ultimately it was deemed so important that it was all state-controlled. The Romans were not unaware of the risks of lead mining so it was done mainly by slaves, and at the height of the Empire 40 000 slaves worked the mines of Spain.

The collapse of the Western Roman Empire brought an end to economic development in Europe for almost 1000 years. The causes of the Fall of Rome were a combination of climate change, plague, economic decline, religious dissent, power politics, and outside pressures. Indeed from 250 onwards, all these factors came into play. As the Earth's climate became colder, northern peoples began to move southwards and invade. Plague appeared and epidemics ravaged the Empire. Meanwhile internal military and religious disputes raged on. Lead was at most a minor factor in Rome's downfall. Was it also a factor in the decline of the British Empire 1500 years later?

After the Dark Ages in Europe, which stretched from 500 to 1000, things began slowly to improve, not least of which was the return of a warmer climate, and with this came renewed agricultural and economic activity -and the reintroduction of lead. It now reappeared in all its old guises, and more: lead-glazed pottery was invented in the twelfth century, and this produced a finer quality of table and kitchenware, but one which brought with it a dangerous increase in lead contamination of the diet; lead printing and lead type appeared in the 1400s, and lead bullets were the preferred weapon from the 1500s onwards.

By the time of the British Empire, the exposure of its leading citizens to lead was comparable to that of the Roman aristocracy. The British relied on lead in many aspects of their daily lives and in addition to the uses known to the Romans - including the adulterating of wine - they also poisoned their food with lead-glazed pottery and their drink with lead crystal and lead pewter. They took lead-based medicines, used hair dyes and cosmetics made from lead compounds. They ate canned foods which were sealed with lead solder and they covered many things with paints consisting mainly of white lead. Lead was also present in the water collected from leaded roofs, and in pubs beer was pumped through lead pipes from the cellar to the taps in the bar. In all these ways lead was in their diet and a comparison of the two empires shows just how exposed to lead their respective citizens were.

Table 12.2 Lead in the Roman and British Empires

Roman Empire 1-400

British Empire 1700-1960

Drinking water

Lead-lined viaducts

Lead piping

Lead storage tanks

Lead storage tanks

Tableware

Lead pewter

Lead pewter

Lead-glazed pottery

Lead-crystal decanters and wine

glasses

Kitchenware

Lead-lined cooking vessels

Lead solder

Food

Leaded wines

Leaded wines

Lead syrup, sapa

Lead solders on canned foods

Paint

White lead

White lead

Red lead

Red lead

Chrome yellow (lead chromate)

Medicinal uses

Lead skin plasters

Lead skin plasters

Lead medicines

Cosmetics

Black lead oxide eye liner

Lead acetate hair dye

Buildings

Lead roofing

Lead roofing

Lead solder

Lead solder

Drinking water was often collected from lead roofs and stored in lead cisterns, and as such could often carry a sizeable amount of dissolved lead. Rainwater dissolves lead because it is slightly acidic and it may pick up as much as 1 mg/litre. These are the sorts of levels that would also be found in water supplies that come through lead pipes in soft water areas and especially if the water had been standing in the pipe for some time. There have been cases of people suffering lead poisoning from such water.

Clearly lead could have been a factor in the decline of the Roman and British Empires if one assumes that their fate lay in the hands of rulers whose brains were affected by the metal. And while lead may have affected the fertility of the Roman population, it certainly did not affect that of the British, who reproduced at such an alarming rate in the 1700s and 1800s that leading thinkers of the time, such as the economist Thomas Malthus (1766-1834), warned that it was likely to increase beyond a point at which there was sufficient food to support it, and that efforts should be made to control human reproduction.

One of the puzzling features of the British Empire was the vigour of its scientists, seamen, inventors, and engineers, who created the wealth on which it was built, and yet it fell apart in the first half of the 1900s, to be replaced by a Commonwealth of Nations, a loose federation of 50 countries, and their dependencies, which still exists. As with the Roman Empire, the lead-laden ruling class of the British Empire must take some of the blame. The decline of their empire was so rapid in the twentieth century that it will always puzzle future historians as to its cause. Clearly lead cannot be blamed for this, but one might speculate that some future historian will conclude that some hidden factor undermined it from within and conclude that lead was the reason.

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