We've been hearing a lot lately about the lead levels in Flint, Michigan, so I thought it might be interesting to learn more about this very common metal and how it can be toxic to the human body.
The Basics about Lead
The chemical element commonly referred to as lead occupies position 82 on the Period Table of the Elements. With an atomic weight of 207.2, it is considered to be a "heavy metal", along with copper, zinc, iron and manganese, but unlike these minerals, which in small amounts are beneficial and actually required by the human body for good health, lead has no known benefits to the body and in fact can cause serious health complications and even fatality, thus it is classified a toxic metal, like mercury and plutonium.
Although lead exists in its native form, it is more commonly found in ore called galena, from which lead is produced via a roasting process. It commonly appears with silver, and is itself a shiny, bluish-white metal, although it tarnishes quickly to the familiar dull grey color upon exposure to air. Lead is a soft metal, extremely malleable and ductile, and its relatively low melting point of 600.65 degrees Kelvin makes it easy to smelt. It is a poor electrical conductor and strongly resistant to corrosion.
History of Lead Use
Lead is one of the oldest, if not the oldest, metals known to mankind. Its history of use goes back at least 7000 years, and it was mentioned in the book of Exodus It is thought to have been discovered and first mined in Anatolia around 6500 BC. It was used in ancient times to make statues, coins, utensils and writing tablets, and the ancient Romans used it in addition for plumbing pipes.
The Romans made much use of lead. Indeed, lead's symbol on the Periodic Table, Pb, stands for plumbum, the Latin name for lead. The Romans called lead plumbum nigirum ("black lead") to distinguish it from plumbum album ("white lead"), which we now call tin.
As can be surmised, the word "plumbing" is derived from the Latin plumbum, as the Romans widely employed lead for use in aqueducts and in indoor plumbing. Romans also made cookware, utensils, and eating and drinking vessels from lead. If there were not already enough opportunity for lead to be ingested on a regular basis, lead was also used to sweeten wine, so it was consumed directly, as well as indirectly from contact with leaden vessels.
Throughout the years this versatile metal has found its way into many different substances and products: lead salts were commonly used in paint, and indeed the Renaissance painter Caravaggio is believed to have died from lead poisoning. Lead has been a very popular component in paint; not just in fine art paints but also in everyday house paint. Lead in house paints was not banned as a toxic substance in the United States until the 1970s, and it is still used in paint in China, accounting for the flurry of recalled children's toys produced in China in recent years.
Lead is used to make items as far-ranging as sinker weights for fishing, typeset fonts for printing, radiation shielding, cable covering (due to its propensity to resist corrosion), ammunition, solder, and as a component of storage batteries, an ingredient in pottery glazes, and an anti-knock additive in gasoline.
But even though lead has been present in many everyday household items over the years, it has proven to be even more dangerous in the workplace. The United States Occupational Safety and Health Administration (OSHA) states, "Lead overexposure is one of the most common overexposures found in industry and is a leading cause of workplace illness." Such diverse industries as construction, pottery, the shipyard industry and general manufacturing have all been affected by issues of occupational lead poisoning.
The Dangers of Lead
As counterintuitive as it may seem, given the way the ancients used the material willy-nilly and indeed that its use continues commonly to this day, there was some awareness even in ancient times that lead was a health hazard: the Greek botanist Nicander noted in the 2 nd century BC the colic and paralysis that affect people suffering from lead poisoning and in the 1 st century CE, Greek physician Dioscorides wrote that lead makes the mind "give way" . Vitruvius, the engineer of Julius Caesar, noted that water from earthenware pipes was more wholesome than that from lead. Disease from toxic metals even had a specific name in Latin, morbi mettalici ("disease from metal") . And this, from the people who invented "plumbing"! There were even early forms of regulation of this toxic substance-after it was determined by 17th-century German physician Eberhard Gockel that lead-contaminated wine had lead to an epidemic of colic, the Duke of Württemberg banned its use as an additive .
Despite all this early warning, lead use boomed during the Industrial Revolution and continued to be a problem not only in the workplace but also in the home, and even the air was dangerous, as leaded gas spewed particulate into the air. It was not until regulations were instituted on a very widespread level that acute lead poisoning became rare, although low-level exposure is still quite common.
Lead Poisoning
Exposure to lead occurs when lead dust or fumes get into the human body. This can happen by inhalation or by ingestion through eating or drinking products that are contaminated by lead or even wild game from which the lead shot has not been thoroughly removed. Lead enters the body and is released to the blood and then distributed throughout the body. Almost the entire body burden of lead is accumulated in the bones. When lead enters the body it is mostly stored in bones, which is why it can be released into the blood long after the initial exposure. The toxicity of lead is well known and documented; lead effects all organs and body functions to different degrees, depending upon exposure level. There are many lead-induced health effects; the following are some of the major ones:
Peripheral neuropathy is a condition in which the nerves that connect the spinal cord and the body become damaged. This damage can prevent proper communication between the brain and the muscles, causing loss of sensation and pain. People suffering from this may also experience weakness, especially in the affected parts of the body.
Encephalopathy is disorder or disease of the brain that can be caused by toxins such as lead. The symptoms of this disorder are altered mental state, loss of cognitive functions (including the inability to concentrate), depression, and seizures.
Some of the gastrointestinal effects of lead poisoning are nausea and impaired digestion, which causes pain in the abdomen and feeling full earlier then expected. Along these lines, there is actually some evidence that lead was appreciated as a diet aid for young ladies in centuries past, as consumption left them pale, slender and langorous, as was the fashion. Early death was not a sought-after result but was not unexpected in those days.
Lead exposure can also cause miscarriages in women and reduced sperm count in males along with abnormal sperm, which can cause reproductive problems. Another disease caused by lead is anemia, which is a decrease in the number of red blood cells, leading to lack of oxygen in organs. This can cause shortness of breath, dizziness, fainting, chest pain, and even heart attack.
The most significant source of lead is contaminated dust, which is created during flood clean up. It poses a great risk to children and pregnant woman. Hazardous lead dust is created when renovations are done by demolitions and cutting which disturbs lead based paint which is harmful to everybody especially children and expecting mothers. Lead based paint was used in more than 38 million homes until it was finally banned for residential use in 1978. Small children are most vulnerable to having leaning disabilities and reduced IQ because of lead exposure.
Lead Regulation and Exposure Prevention
Lead regulation falls under the aegis of the US Environmental Protection Agency (EPA), which maintains regional offices to implement federal environmental programs around the country, each with a Regional Administrator who has designated Regional Lead Coordinators to oversee the development of lead-poisoning prevention efforts within the Region.
Because regulations have been in place for some decades now, people rarely die of lead poisoning, but it is still common to see some level of exposure to the element, so it pays to take care to avoid exposure as much as possible. Stay alert for product recalls, be aware that older homes may contain lead paint and even plumbing (your regional office of the EPA may be able to advise you about the best way to abate these conditions), and try to ensure that you are not consuming food or drink from vessels containing lead paint or lead crystal. Lead may be a useful substance, but it doesn't pay to come in too close contact with it!
Sources:
"Heavy Metal (chemistry)" Wikipedia.org 17 October 2011
http://en.wikipedia.org/wiki/Heavy_metal_(chemistry)
Helemenstine, Anne Marie, PhD. "Lead Facts: Chemical and Physical Properties" About.com, 2001
http://chemistry.about.com/od/elementfacts/a/lead.htm
" Lead Poisoning". Wikipedia.org 26 October 2011
http://en.wikipedia.org/wiki/Lead_poisoning
" Lead." Chemicool Periodic Table. Chemicool.com. 24 Feb 2011. Web 10/28/2011
http://www.chemicool.com/elements/lead.html
" Lead". OSHA.gov. 30 May 2008
http://www.osha.gov/SLTC/lead/index.html
Environmental Protection Agency (EPA)
http://www.epa.gov
Images:
https://pixabay.com/en/font-lead-set-book-printing-705667/
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https://pixabay.com/en/weight-kg-lead-weight-horizontal-340636/
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