intro • Lead has a long and unique history. It has played a important role in the history of mankind. It affected numerous people who suffered from maladies by inhaling or ingesting it. • Many people in the 19th and 20th century regarded it as a magical substance. It was durable and in its heyday, applied to a variety of things • As research confirmed that lead was harmful to humans and the environment, the use of lead has declined greatly.
Lead/Chemistry • Lead is number 82 in the periodic table. It is a bright and silvery metal with high density, malleability, and ductility. It is a poor electrical conductor compared with other metals. Lead is classified as a post transition metal (also called a poor transition metal). When reacting with air, it begins to tarnish by forming compounds. There are three kinds of lead isotopes with different atomic weights respectively —204, 206, and 207.
ANCIENT TIMES 1 • Lead has been thought to exist ever since the Universe was created for about 13.7 billion years. The basic isotopes of lead have existed since the Big Bang, but others have been created by uranium. • Lead was one of the earliest metals discovered and mined by human. Lead mines were found across the ancient world from Athens to Carthage. Different civilizations used lead in different ways. In India, lead was used to make amulets; in China, it was used as a stimulant for the emperor. • Lead was mined across the Roman Empire from Central Europe to what is now Great Britain. Rome was one of the largest users of lead and producer of lead in the ancient world, it is estimated that they produced 800,000 tons of lead per year.
Ancient times 2 • Romans used lead extensively throughout their empire. They used it to smelt silver and used it to make pipes for plumbing and transporting water to citizens throughout the empire. • Hence lead’s symbol on the periodic table: Pbwhich derived from the Latin word meaning plumber. • Romans also used lead in winemaking because wine often turned sour. Adding lead acetate made wine taste sweet. • Some Roman people began to suspect that lead was dangerous after wine drinker suffered from malaise.
Middle ages/Pre-Industrial revolution • After the fall of the Roman Empire, the use of lead declined in Europe and remained at a low level for about 600 years. It was mainly used in stained glass in churches. • When Gutenberg invented the printing press, printing blocks were made from a lead-based alloy. • Artists like Caravaggio suffered and died from lead poisoning because many of the paints they used contained lead.
Industrial Rev./20th century • Lead took a new turn in the Industrial Revolution, it was used in a variety of industries ranging from bullets to cosmetics. • The increased demand brought countless number of people in contact with lead, including women and children. • In the 20th century, lead was used widely in two products: paint and gasoline. • Lead was used in paint because of its durability. Children are vulnerable to lead poisoning because of the sweet taste of lead.
Industrial rev./20th Century(con.) • A scientist for GM discovered that when lead was added gasoline, it reduced engine knocking considerably. • GM and Standard Oil formed a company, called the Ethyl Gasoline Corp. that produced leaded gasoline. • More and more studies in the 1970s confirmed that lead deteriorated intelligence, increased crime rates, and polluted the environment. • Because of mass exposure to lead via gasoline and paint, researchers estimate that crime rate rose 50% percent in the 20th century. • EPA announced leaded gasoline would be phased out in 1973
Today • Today, lead industry is still important although its toxic effect is well-known. • It is estimated that 9.6 million tons of lead was produced in 2010, worthy of more than 10 billion dollars. The top countries that generated the most lead included Australia, China, the United States, Peru, Canada, Mexico, Sweden, Morocco, South Africa, and North Korea. Among them, Australia, China, and the US accounted for more than half of the lead mined. The annual usage of lead per capita is currently eight kilograms around world. At the current rate, the United States Geological Service estimates that the supply of lead may run out in 40 years. • Lead prices per ton have been known to fluctuate.
usages • Lead had a variety of usages. • It was formerly used in paint, gasoline, cosmetics, printing blocks, pesticides, pipes, etc. • Today lead is still used in car-batteries and radiation shielding.
Lead poisoning • There are two kinds of lead poisoning: acute lead poisoning and chronic lead poisoning. Chronic poisoning occurs from long term exposure to small amounts of lead. Symptoms are usually different from person to person. They include weight loss, diarrhea, headaches, weakness, and mental change. • Lead is more harmful to children than adults because it can damage children's developing nervous system. A small amount of lead could reduce the IQ of a child and cause mental retardation.
The future • Lead is not used as widely as it used to be. • The majority of the world’s country have phased out leaded gasoline, only few countries still use leaded gas because of sanctions and wars. • Researchers have estimated that crimes have dropped and intelligence of children have improved after the ban of lead in gasoline and paint. • Lead will continue to be used in some products until safe substitutes are found.