Elemental lead is a heavy, soft, easily worked, bluish metal. Lead deposits are often found in the form of galena, a lead-sulfide mineral associated with zinc sulfides and silver. In fact, lead was recovered in early times as a by-product of the smelting of silver.
Nearly all of the lead in the human environment results from human activities. Once lead is mined, processed, and introduced into the human environment (i.e., the lead that people encounter in their environment), it is a potential problem forever. No current technology will destroy it or make it permanently harmless. However, exposures to lead can be controlled.
Lead has been mined, smelted, and made into products for thousands of years.
The oldest known lead object is an 8,500 year old statue that was excavated in Turkey. Lead objects also have been found in ancient Egyptian tombs that are approximately 8,000 years old. In ancient Syria, lead was fashioned into rods and pieces that were used as money.
World production of lead 4,000 years ago has been estimated at 160 tons per year; 2,700 years ago, production was 10,000 tons per year; and, during the Roman Empire, lead production increased to 80,000 tons per year.
Romans were responsible for developing practical uses for lead; for instance, around 2,300 years ago, the first Roman aqueduct was built to supply the city of Rome with water from a source about seven miles away. Incoming water was distributed through a system of lead pipes. During the Roman Empire, lead was used extensively in many other objects, such as lining vessels that stored water and wine; making utensils; and, in combined form, as glazing on pottery. Some researchers think that the decline of the Roman Empire can be attributed partly to lowered birth rates and increased mental problems caused by lead poisoning.
After the industrial age began in the 1800s, the use of lead increased, and with it, the potential for occupational exposures.
Lead’s versatility, as well as its favorable physical and chemical properties, accounted for its popularity. Much of lead’s usefulness is because it is soft, the softest of all common metals, and easily worked. It can be rolled into sheets that can then be made into rods and pipes. It can be molded into containers and combines with other metals. Consequently, lead has been used in building construction, especially for roofing, cornices, electrical conduits, water pipes, and sewer pipes. Centuries of mining, smelting, and use of lead have released millions of tons of metal into the environment.
Although the ancient Greeks were the first to write about lead poisoning, unfortunately lead has not been recognized as a hazard for most of its long history. In fact, doctors over the years have used lead as a “treatment” for various diseases. A medical dictionary printed in 1745 suggests that lead dissolved in a mild acid such as vinegar could be used to cure sores or skin diseases. Others have claimed that lead therapy could cure consumption, diabetes, dysentery, and epilepsy.
The occupational hazards of lead were first reported in 1713 by Bernardo Ramazzini who described lead intoxication in potters working with lead glazes. In the later part of the 1700s, Benjamin Franklin (who was a printer and handled lead type) described the toxic effects of lead on workers who used lead in their jobs. These workers included printers, plumbers, and painters. In a now famous letter to his friend Ben Vaughan, Franklin wrote of his concern that no one seemed to be doing anything to protect people from the known poisonous nature of lead. In 1913, Dr. Alice Hamilton, an American occupational health doctor, wrote about painters and the hazards of their work. She documented their exposure to lead and their health problems.
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