Lead

Lead (symbol Pb, atomic number 82) is a soft, dense, bluish-gray metal that melts at the relatively low temperature of 328°C (662°F). It has many beneficial uses in compounds as well as in its metallic form, but is toxic at almost any level in the body. Mentioned in the Bible, lead was one of the first known metals. Its toxicity was also recognized long ago; Greek physicians made the first clinical description of lead poisoning in the first century b.c.e., and lead is arguably the earliest known industrial pollutant.

Lead taken internally in any of its forms is highly toxic. At higher body levels, the symptoms of lead poisoning are anemia, weakness, constipation, colic, palsy, and often a paralysis of the wrists and ankles. At low levels, there may be no symptoms. Young children are especially at risk from lead, even at levels once thought safe. Low-level lead poisoning can reduce intelligence, delay motor development, impair memory, and cause hearing problems and troubles in balance.

Higher levels of lead poisoning are reduced with the use of chelating agents that help the body to excrete the lead in urine. Although this may address the physical symptoms mentioned above, there is no cure for the loss of IQ and other neurological effects that lead poisoning has on young children.

Lead was used by the Romans to make water pipes and create elaborate urban water systems. The word plumbing comes from the Latin word for lead, plumbum. Lead was, and still remains, a natural choice for plumbing, Widely available, it is durable and easily malleable , and it does not rust. Water is still delivered to homes in many U.S. cities via lead supply pipes. Alloys of lead are also used in solder and in brass faucets and fixtures. Drinking water can leach lead out of a plumbing system, and this may be one source of lead exposure.

The most common uses of lead today are in lead-acid storage batteries and to shield against radiation. Computer screens are made of leaded glass to contain the electromagnetic radiation within, and as a consequence, two U.S. states have banned the disposal of CRT monitors in landfills and incinerators.

Lead is useful in many compounds. Lead carbonate, called white lead, has been used for over 2,000 years as a white pigment in paint and ceramic glazes, and other lead compounds have been used as pigments and driers . Lead-based paint was first identified as the source of deadly childhood poisoning in Australia in 1904.

Subsequently, lead-based paint was banned in Australia and much of Europe in the 1920s, but the United States did not prohibit its residential use for another fifty years. By 1971 it was determined that two hundred children a year died annually in this country as a result of lead poisoning. That year Congress passed the Lead-Based Poisoning Prevention Act, but delayed implementation of its official ban until 1977.

The lead-based paint applied to homes during the first two-thirds of the twentieth century continues to be the primary cause of childhood lead poisoning. Children who eat flakes of peeling and chipping paint in older, unmaintained housing are at serious risk. The National Survey of Lead and Allergens in Housing for 1998 to 2000 found that some 38 million housing units contain lead-based paint. Some 25 million of these units have "significant" lead-based paint hazards.

Even lead-based paint that is in good condition can pose a risk as the dust created by the friction of opening and closing windows may cause low-level lead poisoning. The renovation of an older home, when done improperly, can poison adults and children as well as pets living in that residence. Residential lead-based paint should never be sanded or burned off.

Lead poisoning is an important health problem, affecting an estimated 890,000 preschoolers, according to the U.S. Centers for Disease Control and Prevention. That means that about 4.4 percent of children aged one to five have unacceptably high levels of lead in their bodies. Although lead poisoning crosses all socioeconomic, geographic, and racial boundaries, the burden of this disease falls disproportionately on low-income families and those of color. In the United States, children from poor families are eight times more likely to be poisoned by lead than those from higher-income families.

Another compound, tetraethyl lead, was once routinely added to gasoline to prevent knocking or premature detonation in internal combustion engines. The lead survived the combustion process and became a significant contributor to air pollution. Leaded gasoline was phased out in the United States starting in 1976. All gasoline-powered cars and trucks now sold in this country must burn unleaded gasoline.

Leaded gasoline nevertheless remains a problem in many other countries. In 1995 fewer than thirty countries worldwide had banned leaded gasoline. In 1996 the World Bank called for the international phasing out of leaded gasoline, claiming that most of the 1.7 billion urban dwellers in developing countries were at risk from lead poisoning. The United Nations Commission on Human Settlements—known as Habitat—approved a resolution in 1999 that committed member nations to begin phasing out leaded gas. By 2001 forty-five nations worldwide had banned its use.

Because lead is an element; it does not biodegrade . Lead pollution from the dawn of civilization remains in the environment. Ice-core researchers in North Greenland have found layers of glacial ice contaminated with lead from ancient Rome's smelters. The lead pollution emitted by smelters can reach staggering levels. In Herculaneum, Missouri, where the nation's largest lead smelter has been in operation for more than one hundred years, health officials documented that almost 28 percent of children under seven have elevated levels of lead in their bloodstream; close to the facility that figure rose to 45 percent. Dust samples along the roads used by trucks serving the smelter contained extremely high concentrations of lead (up to 300,000 parts per million), and the site has been declared an urgent public health hazard.

Enforcement actions by the U.S. Environmental Protection Agency (EPA) and the Missouri Department of Natural Resources led to an agreement by the Doe Run Company, the smelter's owner, to install new controls on air emissions, remediate lead contamination in residential yards, and stabilize a contaminated slag pile located in the Mississippi River flood plain.

Although lead is a persistent and widespread contaminant in both natural and man-made environments, lead poisoning is an entirely preventable disease. The key to prevention is the elimination of sources and pathways . The positive results of bans on leaded gasoline, lead in paints and glazes, lead solder, and lead plumbing can be seen in the reduction in the number of lead-poisoning cases as well as the decreased levels of lead found in the general population.

Bibliography

Stapleton, Richard. (1994). Lead Is a Silent Hazard. New York: Walker and Company.

Warren, Christian. (2001). Brush with Death; A Social History of Lead Poisoning. Baltimore: Johns Hopkins University Press, 2001.

internet resources

Alliance to End Childhood Lead Poisoning. Available at http://www.aeclp.org.

CDC Childhood Lead Poisoning Prevention Program. Available at http://www.cdc. gov/nceh/lead/lead.htm.

Richard M. Stapleton

lead¹ / lēd/ • v. (past and past part. led / led/ ) [tr.] 1. cause (a person or animal) to go with one by holding them by the hand, a halter, a rope, etc., while moving forward: she emerged leading a bay horse. ∎  show (someone or something) the way to a destination by going in front of or beside them: she stood up and led her friend to the door. ∎  be a reason or motive for (someone): nothing that I have read about the case leads me to the conclusion that anything untoward happened a fascination for art led him to start a collection of paintings. ∎  [intr.] be a route or means of access to a particular place or in a particular direction: a door leading to a better-lit corridor. ∎  [intr.] (lead to) culminate in (a particular event): closing the plant will lead to the loss of 300 jobs. ∎  [intr.] (lead on to) form a stage in a process that leads probably or inevitably to (a particular end): his work on digestion led on to study of proteins and fats. ∎  (lead something through) cause a liquid or easily moving matter to pass through (a channel). 2. [tr.] be in charge or command of: a military delegation was led by the Chief of Staff. ∎  organize and direct: the conference included sessions led by people with personal knowledge of the area. ∎  set (a process) in motion: they are waiting for an expansion of world trade to lead a recovery. ∎  be the principal player of (a group of musicians): since the forties he has led his own big bands. ∎  [intr.] (lead with) assign the most important position to (a particular news item): the news on the radio led with the murder. 3. be superior to (competitors or colleagues): there will be specific areas or skills in which other nations lead the world. ∎  have the first place in (a competition); be ahead of (competitors): the veteran jockey was leading the field. ∎  [intr.] have the advantage in a race or game: Dallas was fortunate to lead 85-72. 4. have or experience (a particular way of life): she's led a completely sheltered life. 5. initiate (action in a game or contest), in particular: ∎  (in card games) play (the first card) in a trick or round of play. ∎  [intr.] (lead with) Boxing make an attack with (a particular punch or fist): Adam led with a left. ∎  [intr.] Baseball (of a base runner) advance one or more steps from the base one occupies while the pitcher has the ball: the runner leads from first. • n. / lēd/ 1. the initiative in an action; an example for others to follow: The U.S. is now taking the environmental lead. ∎  a clue to be followed in the resolution of a problem: detectives investigating the murder are chasing new leads. ∎  (in card games) an act or right of playing first in a trick or round of play: it's your lead. ∎  the card played first in a trick or round. 2. (the lead) a position of advantage in a contest; first place: they were beaten 5-3 after twice being in the lead. ∎  an amount by which a competitor is ahead of the others: the team held a slender one-goal lead. ∎ Baseball an advance of one or more steps taken by a base runner from the base they occupy while the pitcher has the ball. 3. the chief part in a play or film: she had the lead in a new film [as adj.] the lead role. ∎  the person playing the chief part: he still looked like a romantic lead. ∎  [usu. as adj.] the chief performer or instrument of a specified type: that girl will be your lead dancer. ∎  [often as adj.] the item of news given the greatest prominence in a newspaper or magazine: the lead story. 4. a leash for a dog or other animal. 5. a wire that conveys electric current from a source to an appliance, or that connects two points of a circuit together. 6. the distance advanced by a screw in one turn. 7. a channel, in particular: ∎  an artificial watercourse leading to a mill. ∎  a channel of water in an ice field. PHRASES: lead someone astray cause someone to act or think foolishly or wrongly. lead someone by the nose inf. control someone totally, esp. by deceiving them. lead someone a dancesee dance. lead from the front take an active role in what one is urging and directing others to do. lead someone up (or down) the garden path inf. give someone misleading clues or signals. lead the waysee way. lead with one's chin inf. (of a boxer) leave one's chin unprotected. ∎ fig. behave or speak incautiously. PHRASAL VERBS: lead off 1. start: the newsletter leads off with a report on tax bills. ∎  Baseball bat first in a game or inning. 2. (of a door, room, or path) provide access away from a central space: a farm track led off to the left. lead someone on mislead or deceive someone, esp. into believing that one is in love with or attracted to them. lead up to immediately precede: the weeks leading up to the elections. ∎  result in: fashioning a policy appropriate to the situation entails understanding the forces that led up to it. lead² / led/ • n. 1. a heavy, bluish-gray, soft, ductile metal, the chemical element of atomic number 82. It has been used in roofing, plumbing, ammunition, storage batteries, radiation shields, etc., and its compounds have been used in crystal glass, as an antiknock agent in gasoline, and (formerly) in paints. (Symbol: Pb) 2. an item or implement made of lead, in particular: ∎  Naut. a lead casting suspended on a line to determine the depth of water. ∎  bullets. 3. graphite used as the part of a pencil that makes a mark. 4. Printing a blank space between lines of print. [ORIGIN: originally with reference to the metal strip used to create this space.] PHRASES: get the lead out inf. move or work more quickly.

LEAD

Lead (Pb) is a soft, corrosion-resistant gray metal that is a common environmental contaminant in air, food, paint, and water. Lead is recovered from mined sulfide ores, and has been used to fashion items such as statues and tools since at least 6500 b.c.e. The Romans used lead to fashion potable water piping. The relationship between plumbing and lead has become a permanent part of the English language—the word "plumbing" derives from the Latin word for lead, plumbum. Besides plumbing, lead has been used to manufacture items such as ceramics, cosmetics, lead batteries, leaded paint, and leaded gasoline. Common chemical species of lead used commercially include lead acetate, lead carbonate, lead chloride, and lead oxide.

Figure 1

The Agency for Toxic Substances and Disease Registry (ATSDR) estimates that more than one million workers in one hundred occupations are exposed to lead, such as in the lead-battery recycling and lead-smelting industries. Equally important, almost all persons are exposed to lead in residential settings from sources such as paint chips, food, water, cigarettes, and clothing that has been worn in lead-contaminated work environments.

Adverse health effects from lead exposure have been recognized since the time of the Romans. The National Research Council (NRC) traces society's more recent interest in lead poisoning to an 1839 publication by Tanquerel des Planches, who described lead colic in 1,207 occupationally exposed workers. It is now recognized that even low levels of lead exposure are associated with adverse health effects. The U.S. Centers for Disease Control and Prevention (CDC) has identified a lead concentration of ten micrograms per deciliter (µg/dL) of blood as the level of concern above which significant health risks occur. Acute exposure to lead compounds may cause brain damage, kidney damage, and gastrointestinal distress. Chronic exposure to lead results in effects on the blood, the central nervous system, blood pressure, the kidneys, the male reproductive system, and vitamin D metabolism. Children, particularly impoverished children living in homes with lead paint, are particularly at risk from the toxic effects of lead, and may exhibit slowed cognitive development and decreased intelligence after chronic exposure. Figure 1 identifies the health effects of lead at different blood level concentrations.

Because lead does not biodegrade, the approximately 300 million metric tons of lead produced to date remains in the environment. This suggests that humans will continue to be exposed to lead despite the phasing out of lead in consumer products such as gasoline and paint. In the early 1970s, the federal government recognized that steps had to be taken to reduce human exposure to lead, and banned residential leaded paint (1978), and phased out leaded gasoline between 1975 and 1995. The removal of lead from gasoline has proceeded more slowly in the rest of the world. In some countries leaded gasoline remains a significant source of exposure.

The CDC estimates that children's blood lead levels have declined over eighty percent since the mid-1970s. The Lead Contamination Act of 1988 authorized the CDC to initiate programs to eliminate childhood lead poisoning in the United States. The Lead Contamination Act of 1988 authorized the CDC to make grants to state and local agencies for comprehensive programs designed to screen infants and children for elevated blood lead levels, ensure referral for medical and environmental intervention for lead-poisoned infants and children, and provide education about childhood lead poisoning. Despite this impressive decrease in blood lead levels, more than one million children in the United States have blood lead levels above 10 µg/dL, and are at risk of permanent neurological impairment.

Margaret H. Whitaker

Bruce A. Fowler

(see also: Blood Lead; Environmental Determinants of Health; Heavy Metals; Occupational Disease; Occupational Safety and Health; Regulations Affecting Housing )

Bibliography

Agency for Toxic Substances and Disease Registry (ATSDR) (1993). Toxicological Profile for Lead. Washington, DC: U.S. Department of Health and Human Services.

—— (2000). Case Studies in Environmental Medicine: Lead Toxicity. Available at http://www.atsdr.cdc.gov/HEC/caselead.html.

Centers for Disease Control and Prevention (1997). "Update: Blood Lead Levels—United States 1991–1994." Morbidity and Mortality Weekly Report 46(7):141–146 and erratum in 46(26):607.

Lewis, J. (1985). "Lead Poisoning: A Historical Perspective." EPA Journal. Available at http://www.epa.gov/history/topics/perspect/lead.htm.

National Research Council, Commission on Life Sciences (1993). Measuring Lead Exposure in Infants, Children, and Other Sensitive Populations. Available at http://stills.nap.edu/books/030904927X/html/.

President's Task Force on Environmental Health Risks and Safety Risks to Children (2000). Eliminating Childhood Lead Poisoning: A Federal Strategy Targeting Lead Paint Hazards. Available at http://www.epa.gov/children/whatwe/leadhaz.pdf.

U.S. Environmental Protection Agency (U.S. EPA) (1998). Lead in Your Home: A Parent's Reference Guide. Office of Prevention, Pesticides, and Toxic Substances. Available at http://www.epa.gov/lead/leadrev.pdf.

Lead

melting point: 327.5°C
boiling point: 1,740.0°C
density: 11.34 g/cm ³
most common ions: Pb ²⁺, Pb ⁴⁺

Lead makes up only about 0.0013 percent of Earth's crust but was well known in the ancient world and was even mentioned in the Book of Exodus. The word "lead" is derived from the Anglo-Saxon word laedan. Lead's symbol, Pb, comes from the Latin word for lead, plumbum. Because of lead's long use in piping, the word "plumber" comes from that same root. Lead is an extremely dense but malleable metal that is very resistant to corrosion.

Lead is sometimes found free in nature but is usually obtained from ores such as galena (PbS) or cerussite (PbCO₃), from which it is easily mined and refined. Most lead is obtained by simply roasting galena in hot air. About one-third of the lead used in the United States is obtained through recycling efforts.

Lead has seen many uses over the ages. As a constituent of pewter (an alloy of tin and lead), lead was a component of Roman eating and drinking utensils. It has been suggested that the decline of the Roman Empire may have been tied to this use, since acidic foodstuffs extract small amounts of lead, a cumulative human poison. Lead's use as a pottery glaze has been banned for the same reason—the danger of lead ingestion via the extraction of the lead by food and drink. During the twentieth century, a volatile form of lead—tetraethyl lead [Pb(CH₂CH₃)₄]—was developed and widely used to improve the octane level of gasoline. That use has also been banned for health and environmental reasons.

Lead remains in wide use in electrical cable sheathing, automobile batteries, lead crystal, radiation protection, and some solders.

see also Inorganic Chemistry; Radioactivity.

George H. Wahl Jr.

Bibliography

Internet Resources

Jefferson Lab. "It's Elemental: The Element Lead." Available from <http://education.jlab.org/itselemental/ele082.html>.

lead A mineral of no nutritional interest, since it is not known to have any function in the body. It is toxic and its effects are cumulative. May be present in food from traces naturally present in the soil or as contamination; from shellfish that have absorbed it from seawater; from lead glazes on cooking vessels; and in drinking water where lead pipes are used. Traces are excreted in the urine.

lead. Heavy, silvery-grey metal, easily beaten, bent, and joined by heat as its melting-point is low. Used as a roof-covering in the Middle Ages, it was also employed for joints between roofs and, e.g., chimneys, and for rainwater-pipes, water-cisterns, etc. In Antiquity it was used to convey water, but the fact that it could pollute drinking water was recognized by the Romans.

lead in alchemy, this metal is associated with Saturn, and is proverbial for its heaviness and low value.
go down like a lead balloon fail, be a flop, (especially of a speech or suggestion) be poorly received. The idea of something plummeting as heavily as a balloon made of lead is recorded from the mid 20th century.

See also swing the lead.

lead2 take with one, conduct; carry on (now mainly with life as obj.) OE.; precede, be foremost (in) XIV(first in lead the dance). OE. lǣdan = OS. lēdian (Du. leiden), (O)HG. leiten, ON. leiða :- Gmc. *laiðjan, f. *laiðō LOAD.
Hence lead sb. XIII. leader late OE. lǣdere.

lead A metal found in the Sinai peninsula and (Ezek. 27: 12) in Tarshish (a town in the west, Jonah 1: 3) and mentioned in Job (19: 24), where he pleads that his words could be chiselled out of a rock and filled with lead to ensure that they would never perish.

Lead , city (1990 pop. 3,632), Lawrence co., W S.Dak., in the Black Hills; laid out 1876 after the discovery of gold there, inc. 1890. It is the site of the famous Homestake Mine, which was in operation from 1877 to 2001.

lead metallic chemical element; symbol Pb [Lat. plumbum ]; at. no. 82; at. wt. 207.2; m.p. 327.502°C; b.p. about 1,740°C; sp. gr. 11.35 at 20°C; valence +2 or +4. One of the oldest metals used by humanity, lead was known to the ancient Egyptians and Babylonians. The Romans used it for pipes and in solder. It was one of the first metals mined in North America, where it was sought after especially for making shot.

Properties and Isotopes

Lead is a dense, relatively soft, malleable metal with low tensile strength. It is a poor conductor of electricity and heat. Lead has a face-centered cubic crystalline structure. It is below tin in Group 14 of the periodic table . Although lead has a lustrous silver-blue appearance when freshly cut, it darkens upon exposure to moist air because of the rapid formation of an oxide film; the film protects the metal from further oxidation or corrosion. All lead compounds are poisonous (see lead poisoning ). Lead resists reaction with cold concentrated sulfuric acid but reacts slowly with hydrochloric acid and readily with nitric acid.

The element has four naturally occurring stable isotopes, three of which result from the decay of naturally occurring radioactive elements ( thorium and uranium ). Since this decay takes place at a constant rate, it is possible to predict either the maximum age of a lead-containing rock or its composition at some earlier date, as long as the rock has not been chemically altered. There are 25 known radioactive isotopes of lead, some of which occur naturally in small amounts.

Natural Occurrence and Processing

Although lead is seldom found uncombined in nature, its compounds are widely distributed throughout the world, principally in the ores galena , cerussite , and anglesite . Australia, the United States, Canada, and Russia are among the chief producers of lead. In the United States galena (a lead sulfide ore) is mined in southern Missouri, with some ore coming from the western states. The ore is concentrated by the flotation process and is then refined by electrolysis or by smelting. About one third of the lead used in the United States is so-called secondary lead, i.e., lead and lead alloys reclaimed chiefly from automobile batteries.

Uses

The single most important commercial use of lead is in the manufacture of lead-acid storage batteries (see battery, electric ). It is also used in alloys such as fusible metals, antifriction metals, solder , and type metal . Shot lead is an alloy of lead, antimony, and arsenic. Lead foil is made with lead alloys. Lead is used for covering cables and as a lining for laboratory sinks, tanks, and the "chambers" in the lead-chamber process for the manufacture of sulfuric acid. It is used extensively in plumbing . Because it has excellent vibration-dampening characteristics, lead is often used to support heavy machinery and was used in the foundations of the Pan Am Building built over Grand Central Station in New York City. Lead is also employed as protective shielding against X rays and radiation from nuclear reactors.

Lead has many commonly used compounds. Commercially important are the lead oxides, which have many uses. Litharge is lead monoxide, PbO; red lead is lead tetroxide, Pb ₃ O ₄ ; lead peroxide or dioxide, PbO ₂ , is used in matches, as a mordant in dyeing, and as an oxidizing agent. White lead , 2PbCO ₃ ·Pb(OH) ₂ (basic lead carbonate), is an important pigment used in paints, putty, and ceramics. Chrome yellow, PbCrO ₄ , is a bright yellow pigment. "Sublimed white lead," PbSO ₄ ·Pb(OH) ₂ (basic lead sulfate), is also used as a pigment. Lead acetate (sugar of lead) is used as a mordant, and lead azide, Pb(N ₃ ) ₂ , is employed as a detonator for explosives. Lead arsenate is used as an insecticide. Tetraethyl lead, used as a antiknock compound in gasoline, is now banned for environmental reasons in the United States and other countries.

Although lead and most of its compounds are only slightly soluble in water, the use of lead pipe to carry drinking water is dangerous, since lead is a cumulative poison that is not excreted from the body (see lead poisoning ). The "lead" of lead pencils does not contain lead; it is a mixture of graphite and clay.

lead1 the heaviest of the base metals. OE. lēad = MLG. lōd (Du. lood) lead, MHG. lōt (G. lot) plummet, solder :- WGmc. *lauda: rel. to Ir. luaidhe, Gael. luaidh.
Hence leaden (-EN3) adj. OE.

Lead, South Dakota/USA Founded in 1876 after the discovery of gold, its name comes from the lode mines, an outcrop of ore being called a ‘lead’.

lead 2 led n.
1. a lead casting suspended on a line to determine the depth of water.

2. bullets.

lead 1 lēd v. be in charge or command of.

lead •abed, ahead, bed, behead, Birkenhead, bled, bread, bred, coed, cred, crossbred, dead, dread, Ed, embed, Enzed, fed, fled, Fred, gainsaid, head, infrared, ked, lead, led, Med, misled, misread, Ned, outspread, premed, pure-bred, read, red, redd, said, samoyed, shed, shred, sked, sled, sped, Spithead, spread, stead, ted, thread, tread, underbred, underfed, wed •trackbed • flatbed • deathbed •airbed • daybed • seabed •reed bed, seedbed •sickbed • childbed • hotbed • roadbed •footbed • sunbed • sofa bed •waterbed • feather bed • breastfed •dripfed • spoonfed • Szeged •blackhead •cathead, fathead, Flathead •masthead •bedhead, deadhead, redhead •egghead •airhead, stairhead •railhead • maidenhead • Gateshead •beachhead • greenhead • meathead •bighead • bridgehead •dickhead, thickhead •pinhead, skinhead •pithead • Holyhead • sleepyhead •fountainhead • whitehead • godhead •blockhead •drophead, hophead, mophead •hothead • hogshead •sorehead, warhead •Roundhead • bonehead • arrowhead •bullhead • wooden-head • sub-head •bulkhead •chucklehead, knucklehead •drumhead • muttonhead • spearhead •go-ahead • dunderhead • figurehead •loggerhead • hammerhead •letterhead • bobsled • cirriped • biped •moped • quadruped •accede, bead, Bede, bleed, breed, cede, concede, creed, deed, Eid, exceed, feed, Gide, God speed, greed, he'd, heed, impede, interbreed, intercede, Jamshid, knead, lead, mead, Mede, meed, misdeed, mislead, misread, need, plead, proceed, read, rede, reed, Reid, retrocede, screed, secede, seed, she'd, speed, stampede, steed, succeed, supersede, Swede, tweed, weak-kneed, we'd, weed •breastfeed • greenfeed • dripfeed •chickenfeed • spoonfeed • nosebleed •Nibelungenlied • invalid • Ganymede •Runnymede • airspeed • millipede •velocipede • centipede • Siegfried •filigreed • copyread • crossbreed •proofread • flaxseed • hayseed •rapeseed • linseed • pumpkinseed •aniseed • oilseed • birdseed • ragweed •knapweed • seaweed • chickweed •stinkweed • blanket weed • bindweed •pondweed • duckweed • tumbleweed •fireweed • waterweed • silverweed