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EspañolLEAD POISONING
'Lead poisoning' is a medical condition, also known as 'saturnism,' 'plumbism' or 'painter's colic', caused by increased blood lead levels. Lead may cause irreversible neurological damage as well as renal disease, cardiovascular effects, and reproductive toxicity.
Humans have been mining and using this heavy metal for thousands of years, poisoning themselves in the process due to accumulation and exposure. The dangers have also long been known. Reducing the hazard requires both individual actions and public policy regulations. Blood lead levels once considered safe are now considered hazardous, with no known threshold.[1]
History
Lead was first mined in Asia Minor (today Turkey) about 6500 BC. A 6000- to 8000-year-old lead necklace was found in the ancient city site of Anatolia. Lead's easy workability, low melting point and corrosion resistance were among its attractions.
Lead toxicity was first recognized as early as 2000 BC. Nicander of Colophon wrote of lead-induced anemia and colic in 250 BC.[1] Gout, prevalent in affluent Rome, is thought to be the result of lead, or leaded eating and drinking vessels. Lead was used in makeup. Lead sugar (lead acetate) was used to sweeten wine, and the gout that resulted from this was known as saturnine gout.[2]
Aulus Cornelius Celsus, writing ca. 30 AD, listed white lead on a list of poisons with antidotes (beside cantharides, hemlock, hyoscyamus, poisoned mushrooms, and a swallowed leech), and claimed it could be remedied by mallow or walnut juice rubbed up in wine[3] — an interesting idea.[4][5] Despite his awareness of lead's toxicity, citing many contemporary authorities, Celsus recommended its use in a wide range of ointments applied to wounds to stop bleeding and reduce infection or inflammation.[6]
Julius Caesar's engineer, Vitruvius, who also served his successor Caesar Augustus, reported, "Water is much more wholesome from earthenware pipes than from lead pipes. For it seems to be made injurious by lead, because white lead paint is produced from it; and this is said to be harmful to the human body."[7] It should be noted that the prevalence of lead poisoning, at least that caused by drinking water containing lead, in ancient Rome is far less than what is traditionally believed. The hardness of Rome's water caused heavy deposits of calcium carbonate to form on pipes and in turn prevented the lead of the pipes from coming into contact with the water, thus reducing any chance of getting lead poisoning from drinking water.
In 17th-century Germany, an Ulm physician noticed that monks who did not drink wine were healthy, while wine drinkers developed colic. The culprit was a white oxide of lead, litharge, added to sweeten the wine.[8]
Chinese alchemists found that lead could be rendered harmless by soaking it in blood and firing it, when this process was repeated several times it provided a protective coat that lead could not pass. The only notable use of this measure was by martial artists so they could use the heavy metal as weights for training.
Today, most exposure in developed countries is the result of occupational hazards, leaded paint, and leaded gasoline (which continues to be phased out in most countries). Lead poising interferes with the normal development of the brain.
The term "lead poisoning" is sometimes used as a dysphemism for gunshot wounds, as almost all bullets are mainly composed of lead. Despite this, bullets lodged in the body rarely cause significant levels of lead poisoning.[9] Bullets lodged in the joints are the exception, as they deteriorate and release lead into the body over time.[10]
Symptoms and effects
The symptoms of chronic lead poisoning include neurological problems, such as reduced cognitive abilities, or nausea, abdominal pain, irritability, insomnia, metal taste in oral cavity, excess lethargy or hyperactivity, headache and, in extreme cases, seizure and coma. There are also associated gastrointestinal problems, such as constipation, diarrhea, vomiting, poor appetite, weight loss, which are common in acute poisoning. Other associated effects are anemia, kidney problems, and reproductive problems.
In humans, lead toxicity sometimes causes the formation of a bluish line along the gums, which is known as the "Burton's line", although this is very uncommon in young children. Blood film examination may reveal "basophilic stippling" of red blood cells, as well as the changes normally associated with iron deficiency anemia (microcytosis and hypochromia).
A direct link between early lead exposure and extreme learning disability has been confirmed by multiple researchers and child advocacy groups.
A May 2000 study by economic consultant Rick Nevin theorizes that lead exposure explains between 65% to over 90% of the variation in violent crime rates in the U.S. and other countries.[11][12]. The results were discussed in the July Washington Post article, reviving interest in the subject[13]. The result is somewhat supported by Dartmouth Political Scientist Roger D. Masters' work,[14] and similar work is being done by other researchers. Amherst economist Jessica Reyes' working paper,[15] Masters' work are both pre-publication and available online.
Biological role
Lead has no known biological role in the body. The toxicity comes from its ability to mimic other biologically important metals, the most notable of which are calcium, iron and zinc. Lead is able to bind to and interact with the same proteins and molecules as these metals, but after displacement, those molecules function differently and fail to carry out the same reactions, such as in producing enzymes necessary for certain biological processes.
Most lead poisoning symptoms are thought to occur by interfering with an essential enzyme Delta-aminolevulinic acid dehydratase, or ALAD. ALAD is a zinc-binding protein which is important in the biosynthesis of heme, the cofactor found in hemoglobin. Lead poisoning also inhibits the enzyme ferrochelatase which catalyzes the joining of protoporphyrin IX and Fe2+ to form a Heme. Genetic mutations of ALAD cause the disease porphyria, a disease which was highlighted in the movie ''The Madness of King George''. Lead poisoning is sometimes mistaken for porphyria but the distinction is that lead poisoning usually causes anemia while true porphyria does not.
An article on Lead Encephalopathy on Emedicine states:
Lead also interferes with excitatory neurotransmission by glutamate, which is the transmitter at more than half the synapses in the brain and is critical for learning. The glutamate receptor thought to be associated with neuronal development and plasticity is the N-methyl-D-aspartate (NMDA) receptor, which is blocked selectively by lead. This disrupts long-term potentiation, which compromises the permanent retention of newly learned information.[16]
The January 2004 edition of ''Scientific American'' magazine contained an article on schizophrenia that said the latest research:
... implies that their brain circuits reliant on NMDA receptors are out of kilter. If reduced NMDA receptor activity prompts schizophrenia's symptoms, what then causes this reduction? The answer still remains unclear.
However, a Johns Hopkins report by Tomas Guilarte stated:
It has been known for some time that lead is a potent inhibitor of the NMDA receptor, a protein known to play an important role in brain development and cognition. In this study we demonstrate that lead exposure decreased the amount of NMDA receptor gene and protein in a part of the brain called the hippocampus.[17]
Ezra Susser and his colleagues at Columbia University in New York followed 12,000 children born in Oakland, California, between 1959 and 1966, whose mothers had given samples of blood serum while they were pregnant, which were frozen and stored for later analysis. They found that children who had been exposed to high levels of lead in the womb were more than twice as likely to go on to develop schizophrenia. Their research was presented at the 2004 annual meeting of the American Association for the Advancement of Science in Seattle, Washington.
Lead poisoning can also be fatal.
Occurrence
Outside of occupational hazards, the majority of lead poisoning occurs in children under age twelve. The main sources of poisoning are from ingestion of lead contaminated soil (this is less of a problem in countries that no longer have leaded gasoline) and from ingestion of lead dust or chips from deteriorating lead-based paints. This is particularly a problem in older houses where the sweet-tasting lead paint is likely to chip, but deteriorating lead-based paint can also powder and be inhaled. Small children also tend to teethe and suck on painted windowsills as they look outside. In most American states, landlords and those selling such houses are required to inform the potential residents of the danger.
Lead has also been found in drinking water. It can come from plumbing and fixtures that are either made of lead or have trace amounts of lead in them.[18] Exposure to metallic lead such as small lead objects, can rarely lead to an increase in blood lead levels if the lead is retained in the gastrointestinal tract or appendix.
Lead can also be found in some imported cosmetics such as Kohl, from the Middle East, India, Pakistan, and some parts of Africa, and Surma from India and from imported toys, such as many made in China. There are also risks of elevated blood lead levels caused by folk remedies like Azarcon which contains 95 percent lead and is used to "cure" empacho. For more information about less common causes of elevated blood lead levels, see footnote.[19]
Lead may be contracted through the mucous membranes through direct contact to mouth, nose, eyes, and breaks in skin.
Measurement
One measure of lead in the body is the blood lead level (BLL), measured in micrograms of lead per deciliter of blood (μg/dL). Nearly everyone has a measurable BLL. The Centers for Disease Control and Prevention (CDC) states that a BLL of 10 μg/dL or above is a cause for concern. However, lead can impair development even at BLLs below 10 μg/dL.[20] However, BLL measures current exposure to lead, but lead may also be incorporated into bone from prior exposures that will not show in BLLs until this bone-lead becomes "mobilized" through pregnancy or fracture healing. A fetus can be poisoned in utero if its mother had high bone-lead from either childhood exposure or a later occupational or other exposure that is subsequently mobilized by the fetal need for calcium. K-fluorescent X-ray metering can measure bone-lead.
Portable X-ray fluorescence (XRF) equipment can be used to measure lead concentrations and exposures in the field, from lead paint, children's toys, etc. Simple inexpensive test kits are available, which show color changes based on chemical reactions, but they are inexact.
Exposures and demographics
The average person has less than 10 micrograms per deciliter, or 100 parts per billion, ppb, of lead in their blood. People who have been exposed to an unusual amount of lead will have blood lead levels higher than 200 ppb—most clinical symptoms of lead poisoning begin at around 100 ppb. The effect on children's mental/cognitive abilities has been noted at very low levels.[21]
The levels found today in most people are orders of magnitude greater than that of ancient times. These levels are within an order of magnitude of levels that have resulted in adverse health effects.[22] Blood lead levels once considered safe are now considered hazardous, with no known threshold.[23]
pathways
Today almost everyone is exposed to environmental lead. Exposure to lead and lead chemicals can occur through inhalation, ingestion or occasionally dermal contact. Lead mining and lead smelting are common in many countries, where children and adults can receive substantial lead exposure from sources uncommon today in the U.S. Most countries will have phased out use of leaded gasoline by 2007. Lead exposure in the general population (including children) occurs primarily through ingestion, although inhalation also contributes to lead body burden and may be the major contributor for workers in lead-related occupations. Inhalation is the second major pathway of exposure. Almost all inhaled lead is absorbed into the body, whereas from 20% to 70% of ingested lead is absorbed (with children generally absorbing a higher percentage than adults do). Dermal exposure plays a role for exposure to organic lead among workers, but is not considered a significant pathway for the general population, except in areas where leaded gasoline is used. Organic lead from gasoline additives may be absorbed directly through the skin.[24]
children
Lead-contaminated household dust is the major source of lead exposure to children in the U.S.[25]
In 1978 there were 13.5 million children in the United States with elevated blood lead levels (i.e., 10µg/dl). By 2002, that number had dropped to 310,000 kids.[26] The U.S. incurs $43.4 billion annually in the costs of all pediatric environmental disease, with childhood lead poisoning alone accounting for the vast majority of it.[25]
adults
Although children are at greater risk from lead exposure, adult exposures can also result in harmful health effects. Most adult exposures are occupational and occur in lead-related industries such as lead smelting, refining, and manufacturing industries. One frequent source of lead exposure to adults is home renovation that involves scraping, remodeling, or otherwise disturbing lead-based paint. Adults can also be exposed during certain hobbies and activities where lead is used. Workers may inhale lead dust and lead oxide fumes, as well as eat, drink, and smoke in or near contaminated areas, thereby increasing their probability of lead ingestion. Between 0.5 and 1.5 million US workers are exposed to lead in the workplace (ATSDR, 1999). Other than the developmental effects unique to young children, the health effects experienced by adults from adult exposures are similar to those experienced by children, although the thresholds are generally higher.[28]
Regulation
US Rules and Regulations
See United States Environmental Protection Agency: Rules and Regulations for its jurisdiction and regulations.
"In 1998, the US Government instituted regulations which limit the amount of lead in toys and other consumer products which are expected to be used by infants to 0.06% (or 600 ppm)."[29]
Ten µg/dL (micrograms /deciliter) was adopted by CDC in 1991 as an action level for children, an advisory level for environmental and educational intervention. There are requirements that children receiving Medicaid be screened. Most states ask or require primary care physicians and persons in charge of screening programs to report both presumptive and confirmed cases of lead toxicity to the appropriate health agency. This is to ensure abatement of the lead source, education of the patient, and remediation steps are undertaken. In some states, the clinical laboratories performing blood lead testing are required to report cases of lead toxicity.
Workplace Air
The OSHA Lead Standard specifies the permissible exposure limit (PEL) of lead in the workplace, the frequency and extent of medical monitoring, and other responsibilities of the employer. OSHA has set a PEL (enforceable) of lead in workplace air at 50 µg/m3 averaged over an 8-hour workday for workers in general industry. NIOSH at CDC has set a Recommended Exposure Limit (REL) of 50 µg/m3 to be maintained so that worker blood lead remains < 60 µg/dL of whole blood.[30] The ACGIH has set a threshold limit value for a time-weighted average (TLV/TWA) of 50 µg/m3 for lead in workplace air (except for lead arsenate).[31]
Lead contaminated soil can pose a risk through direct ingestion, uptake in vegetable gardens, or tracking into homes. Uncontaminated soil contains lead concentrations less than 50 ppm but soil lead levels in many urban areas exceed 200 ppm. (AAP 1993) The EPA’s standard for lead in bare soil in play areas is 400 ppm by weight and 1200 ppm for non-play areas. This regulation applies to cleanup projects using federal funds. The soil screening level (SSL) for lead represents a conservative estimate for a level that would be protective of public health in residential soils based on an analysis of the direct ingestion pathway for children.
EPA has set drinking water standards with two levels of protection. The maximum contaminant level goal (MCLG) is zero. This is the level determined to be safe by toxicological and biomedical considerations, independent of feasibility. EPA’s final rule establishes an action level is set at 15 µg/L. The use of lead solder and other lead-containing materials in connecting household plumbing to public water supplies was banned by EPA as of June 1988.
FDA has set a number of action levels (enforceable) and levels of concern for lead in various food items. These levels are based on FDA calculations of the amount of lead a person can consume without ill affect. FDA has set an action level of 0.5 µg/mL for lead in products intended for use by infants and children and has banned the use of lead-soldered food cans. (FDA 1994 and FDA 1995 as cited in ATSDR 1999)
House paint contained up to 50% lead before 1955. Federal law lowered the amount of lead allowable in paint to 1% in 1971. The CPSC has limited since 1977 the lead in most paints to 0.06% (600 ppm by dry weight). Paint for bridges and marine use may contain greater amounts of lead.[32]
Treatment
Although the most important part of treating lead poisoning is decreasing exposure to lead, there are some forms of chelation therapy that can be used to reduce existing BLL levels:
★ DMSA
★ EDTA
★ British anti-Lewisite
Additionally, a comparative study of chelating agents showed that vitamin C (ascorbic acid), along with DMSA, CDTA and DMPS increased survival in an animal model of lead intoxication, while EGTA, N-acetyl-L-cysteine (NAC) and various other agents did not.[33] High serum levels of vitamin C have been associated with a decreased prevalence of elevated blood lead levels[34] and intervention with supplemental vitamin C was shown to markedly decrease lead levels in smokers (mean: 81 %). Authors hypothecize, however, that this effect might be due to an inhibition of lead absorption.[35]
Famous cases of lead poisoning
★ Much of Ancient Rome's affluent class suffered from lead-induced gout.[36]
★ The Devon colic was caused by the presence of lead in cider in 18th century Devon.
★ Many historians have believed that Ludwig van Beethoven suffered from lead poisoning. This belief has been confirmed in 2005 by tests done at Argonne National Laboratory in the US on skull bone fragments, confirming earlier tests on hair samples.
★ Francisco Goya was considered skilled but unremarkable until he contracted lead poisoning in his late forties and painted a series of disturbing paintings called "the Caprices."[37]
★ George Frideric Handel is believed to have acquired saturnine gout through port wine.[38]
★ Lead shot for hunting ducks and other waterfowl in wetland areas is often restricted because waterfowl can ingest spent shot while feeding from the bottom of lakes and ponds. Non-toxic alternatives such as bismuth or powdered metal/polymer shot is manufactured specifically for use in restricted habitat areas.
★ Operation of a smelter in Trail, British Columbia contributed to higher than average blood lead levels in children living in Trail compared to nearby communities.
★ In 1845, a crew of 128 gathering magnetic data in the Canadian Arctic, under the leadership of John Franklin, are thought to have died from lead poisoning among other things. The canned food on board was sealed in tin cans with lead solder. The lead is thought to have leaked into the food and driven the men mad.[39]
References
1. Lead poisoning, Needleman H, , , Annu Rev Med, 2004
2. The Severe Gout of Emperor Charles V, Couper RTL., , , N Engl J Med, 2006
3. Book V. p 126, de Medicina, Aulus Cornelius Celsus [2],
4. Damage to plants due to industrial pollution and their use as bioindicators in Egypt, , Esmat A., Ali, Environmental Pollution, 1993
5. Evidence of the involvement of plant ligno-cellulosic structure in the sequestration of Pb: an X-ray spectroscopy-based analysis, , Marta, Marmiroli, Environmental Pollution, 2005
6. Book V., de Medicina, Aulus Cornelius Celsus [3]
7. Chapter 6, paragraphs 10 and 11, of Book VIII by Vitruvius [4]
8. Josef Eisinger, "Lead and Wine - Eberhard Gockel and the Colica Pictonum" [5]
9. A fatal case of lead poisoning due to a retained bullet
10. Increased lead absorption and lead poisoning from a retained bullet
11. Research Links Lead Exposure to Changes in Violent Crime Rates Throughout the 20th Century
12. How Lead Exposure Relates to Temporal Changes in IQ, Violent Crime, and Unwed Pregnancy, Nevin, Rick, , , Environmental Research,
13. Research Links Lead Exposure, Criminal Activity
14. Toxins, Brain Chemistry, and Behavior Masters, Roger D.
15. Environmental Policy as Social Policy? The Impact of Childhood Lead Exposure on Crime Reyes, Jessica Wolpaw
16. eMedicine - Lead Encephalopathy : Article by Christopher P Holstege, MD, FACEP, FACMT
17. How Lead Changes the Brain to Impair Learning and Memory, How Lead Changes the Brain to Impair Learning and Memory
18. Lead in drinking water
19. Childhood Lead Poisoning Prevention Program
20. Lead and Brain Injury
21. Low Level Environmental Lead Exposure And Children's Intellectual Function: an International Pooled Analysis Lanphear, Hornung, et al
22. Lead Toxicity: What is Lead?
23. Lead Toxicity Cover Page
24. Lead Toxicity: How Are People Exposed to Lead?
25. Lead Toxicity Cover Page
26. Lead in Paint, Dust, and Soil
27. Lead Toxicity Cover Page
28. Lead Toxicity: Who Is at Risk of Lead Exposure?
29. Detecting Lead in Paint on Toys With Handheld Scanner From Oxford Instruments
30. NIOSH Pocket Guide to Chemical Hazards
31. home page
32. Lead Toxicity Cover Page
33. Treatment of acute lead intoxication. A quantitative comparison of a number of chelating agents, Llobet JM, Domingo JL, Paternain JL, Corbella J, , , Arch Environ Contam Toxicol, 1990
34. Relationship of ascorbic acid to blood lead levels, Simon JA, Hudes ES, , , JAMA, 1999
35. The effect of ascorbic acid supplementation on the blood lead levels of smokers, Dawson E, Evans D, Harris W, Teter M, McGanity W, , , J Am Coll Nutr, 1999
36. Lead and the Fall of Rome: A Bibliography
37. Physical and psychological profile
38. The "Case" of George Frideric Handel
39. Franklin Saga Deaths: A Mystery Solved? National Geographic Magazine, Vol 178, No 3, Sep 1990
Other meanings
The phrase "lead poisoning" is sometimes used as slang for death by shooting, as bullets and shot are usually made of lead.
See also
★ Restriction of Hazardous Substances Directive -- RoHS Lead regulation in Europe
★ Lead paint
External links
★ National Resource for Lead Poisoning Prevention Information
★ Argonne Lab confirms Beethoven lead poisoning, Dec. 2005
★ Case Studies in Environmental Medicine (CSEM): Lead Toxicity
★ Helping Parents Prevent Lead Poisoning
★ History of lead poisoning in the world
★ National Pollutant Inventory - Lead and Lead Compounds Fact Sheet
★ ToxFAQs™: Lead
★ [6]
★ Plumbism in the pottery industry
★ Environmental Quality Institute - Lead Poisoning Prevention Progam
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