LEAD

1. LEAD Bio 2b seminar By David Vo

2. What is Lead?? • Lead is a naturally occurring bluish-gray metal found in small amounts in the earth's crust.  • It has no characteristic taste or smell.  • Metallic lead does not dissolve in water and does not burn.  • Lead can combine with other chemicals to form what are usually known as lead compounds or lead salts.  • Some lead salts dissolve in water better than others.  • Some natural and manufactured substances contain lead but do not look like lead in its metallic form.  • Some of these substances can burn—for example, organic lead compounds in some gasoline. 

3. Lead: the Versatile Metal Its softness and low melting point make lead very easy to handle Its high resistance to corrosion makes it ideal for weatherproofing buildings and for equipment used in the manufacture of acids

4. Protection • Lead’s high density makes it particularly appropriate as a a shield against radiation in the nuclear industry and in hospitals and its also good at stopping sound waves which is good in the blocking the noise from the machinery in factories and from engine rooms on ships.

5. The Chemical:Lead • Lead in soil is in the +2 oxidation state. In its natural state PbS (galena) will become insoluble in reduced soils due to precipitation with sulphide. • Lead +2 ions become less soluble as soil pH rises. • At high pH it will precipitate as a carbonate, hydroxide or phosphate, also in alkaline soils solubility may increase by the formation of soluble Pb-organic and Pb-hydroxy complexes. • Pb2+ has a strong complexation with organic matter leading to bioaccumulation in the humus rich topsoil. • Therefore soils polluted with atmospheric lead have little leaching over many years. Note, however that lead acetate forms a strong soluble complex in water.

6. Lead’s early history • Early uses of lead included building materials, pigments for glazing ceramics, and pipes for transporting water.   • The castles and cathedrals of Europe contain considerable quantities of lead in decorative fixtures, roofs, pipes, and windows.  

7. Continue… • Prior to the early 1900's, uses of lead in the United States were primarily for ammunition, brass, burial vault liners, ceramic glazes, leaded glass and crystal, paints or other protective coatings, pewter, and water lines and pipes.   • With the growth in production of public and private motorized vehicles and the associated use of starting-lighting-ignition (SLI) lead-acid storage batteries and terne metal for gas tanks after World War I

8. Sources and Production • About 3 million tons of lead is mined in the world each year. • Australia, China and the United States account for more than 50% • The most common lead ore is galena or lead sulphide, but the common ones are zinc and silver. • Lead is obtain from ores by a process called smelting. • This involves roasting the ore to remove the sulphur and to obtain lead oxide which is then reacted with coke in a furnace. But then it has to be refined to remove the impurities

9. Where is Lead Found? • Paint. • Many homes built before 1978 have lead-based paint. • In soil around a home, where it can pick up lead from exterior paint or from soil tracked into a home. • Household dust • Dust can pick up lead from deteriorating lead-based paint or from soil tracked into a home.

10. Continue… • Drinking water. • Your home might have plumbing with lead or lead solder. If you can’s see, smell, or taste lead, it doesn’t mean that its not there • The job. • If you work with lead, you can bring it home on your hands and clothes • Old painted toys and furniture • Food and liquids stored in lead crystal or lead-glazed pottery or porcelain

11. Uncommon sources of lead exposure in children • High Amount Sources • Water boiled in leaded pots and pans • Foreign cosmetics: Kohl, Surina • Foreign cold medicines: Azarcon 93.5%, (also Rueda, Coral, Alarcon, Liga, Maria Luisa); Pay-loo-ah 90% lead with arsenic; Yogran Guggulu • Medium Amount Sources • Soil from smelter area • Ceramics • Low Amount Sources • Old newsprint • Leaded crystal • Other sources of lead exposure • Leaded gasoline fumes • Leaded soldering fumes • Leaded foil wine bottle caps

12. Natural distribution • The average level of lead in the lithosphere is 16 ppm • Lead tends to be enriched in soils with concentrations in the range of 2 to 200 ppm • Studies of ice cores in the northern hemisphere indicate lead levels have increased from zero level in 2800 years ago to above 0.2 ppb in 1950.

13. Impacts on vegetation • Lead appears to be unavailable to plant parts. • If lead is absorbed it concentrates in the roots of plants. Foliage contamination is due to soil particles from splash and/or the atmosphere.

14. Lead Being Banned • Lead and Copper Rule 1991 • The rule aimed to minimize lead and copper in drinking water, primarily by reducing water corrosivity • Lead Contamination Control Act of 1988 • The U.S. Department of Health and Human Services has set as an objective the elimination of elevated blood lead levels (BLLs) in children in the United States by the year 2010 • an interim goal, specified as a national health objective for the year 2000, is to reduce BLLs greater than 15 ug/dL and greater than 25 ug/dL among children aged 6 months-5 years to no more than 500,000 and zero, respectively (objective 11.4) • screen infants and children for elevated BLLs, • ensure referral for medical and environmental intervention for lead-poisoned infants and children • ensure referral for medical and environmental intervention for lead-poisoned infants and children

15. Lead in Gasoline • Before the use of leaded gasoline was banned, most of the lead released into the U.S. environment came from car exhaust.  • In 1979, cars released 94.6 million kilograms (kg; 1 kg equals 2.2 pounds) of lead into the air in the United States.  • In 1989, when the use of lead was limited but not banned, cars released only 2.2 million kg to the air.  • Since EPA banned the use of leaded gasoline for highway transportation in 1996, the amount of lead released into the air has decreased further.

16. Lead poison symptoms • Symptoms: • irritation of the alimentary canal; spasm; nervous symptoms; paralysis, either partial or complete. • When taken for some time, in small quantity, • violent and obstinate colic; rigidity of abdominal muscles, cramps; remission of pain; obstinate constipation, urine diminished, saliva increased; countenance anxious and gloomy. • If relief be not promptly obtained, • giddiness, debility, torpor, coma, convulsions and death. The paralysis affects generally the upper extremities.

17. … • Lead poisoning, or plumbism, a disease of occupations, which is itself the cause of organic disease, particularly of the nervous and urinary systems. • The workpeople affected are principally those engaged in potteries where lead-glaze is used; but other industries in which health is similarly affected are filemaking, house-painting and glazing, glass-making, copperworking, coach-making, plumbing and gasfitting, printing, cutlery, and generally those occupations in which lead is concerned.

18. More symptoms… • The symptoms of chronic lead poisoning vary within very wide limits, from colic and constipation up to total blindness, paralysis, convulsions and death.

19. Protecting Your home • If you suspect that your house has lead hazards, you can take some immediate steps to reduce your family's risk:  • If you rent, notify your landlord of peeling or chipping paint.  • Clean up paint chips immediately.  • Clean floors, window frames, window sills, and other surfaces weekly. Use a mop, sponge, or paper towel with warm water and a general all-purpose cleaner or a cleaner made specifically for lead. Thoroughly rinse sponges and mop heads after cleaning dirty or dusty areas.  • Wash children's hands often, especially before they eat and before nap time and bed time. • Keep children from chewing window sills or other painted surfaces.  • Make sure children eat nutritious, low-fat meals high in iron and calcium, such as spinach and dairy products.  Children with good diets absorb less lead. 

20. Latest controversy • powdered candy called Lucas Limon has been found on sale in Adams Morgan for 39 cents a pack. The candy mixes salt and limejuice for a salty and sweet taste. • The product is also used as a food seasoning. • It was removed from the market last year. However, congressional staffers spotted it, and alerted city officials

21. Work Cited • http://www.wjla.com/news/stories/0405/224240.html • http://www.antiquusmorbus.com/English/Poison.htm • http://wpspaint.com/Library/Lead_Paint/lead_Prevention.htm • http://www.atsdr.cdc.gov/toxprofiles/phs13.html • http://www.nsc.org/library/facts/lead.htm • http://www.hud.gov/offices/lead/leadsaferule/index.cfm • http://minerals.usgs.gov/minerals/pubs/commodity/lead/ • http://www.epa.gov/lead/leadinfo.htm#where • http://www.chemicalelements.com/elements/pb.html