| Chemical Abstract Number (CAS #) |
7439-92-1 |
| Synonyms |
| PLUMBUM |
| CI-pigment-metal-4 |
| CI-77575 |
| KS-4 |
| Lead-flake |
| Lead-S2 |
| Olow- (Polish) |
| Pb-S 100 |
| Analytical Methods |
200.7 |
| 200.8 |
| Molecular Formula |
Pb |
Synopsis
|
Lead-(Anglo-Saxon lead),Pb(L.plumbum);at.wt.207.2(l);at.no.82;m.p.327.46'C;b.p.1749'C;sp.gr.11.35(20'C);valence2or4.
Long known, mentioned in Exodus. The alchemists believed lead to be the
oldest metal and associated it with the planet Saturn. Native lead occurs
in nature, but it is rare. Lead is obtained chiefly from galena (PbS) by
a roasting process. Anglesite (PbSO4), cerussite (PbCO3), and minim (Pb3O4)
are other common lead minerals. Lead is a bluish-white metal of bright
luster, is very soft, highly malleable, ductile, and a poor conductor of
electricity. It is very resistant to corrosion; lead pipes bearing the
insignia of Roman emperors, used as drains from the baths, are still in
service. It is used in containers for corrosive liquids (such as sulfuric
acid) and may be toughened by the addition of a small percentage of antimony
or other metals. Natural lead is a mixture of four stable isotopes: 204Pb
(1.4%), 206Pb (24.1 %), 207Pb (22.1 %), and 208Pb (52.4%). Lead isotopes
are the end products of each of the three series of naturally occurring
radioactive elements: 206Pb for the uranium series, 207Pb for the actinium
series, and 208Pb for the thorium series. Forty other isotopes of lead,
all of which are radioactive, are recognized. Its alloys include solder,
type metal, and various antifriction metals. Great quantities of lead,
both as the metal and as the dioxide, are used in storage batteries. Much
metal also goes into cable covering, plumbing, ammunition, and in the manufacture
of lead tetraethyl. The metal is very effective as a sound absorber, is
used as a radiation shield around X-ray equipment and nuclear reactors,
and is used to absorb vibration. White lead, the basic carbonate, sublimed
white lead (PbSO4) chrome yellow (PbCrO4), red lead (Pb3O4), and other
lead compounds are used extensively in paints, although in recent years
the use of lead in paints has been drastically curtailed to eliminate or
reduce health hazards. Lead oxide isused in producing fine "crystal glass"
and "flint glass" of a high index of refraction for achromatic lenses.
The nitrate and the acetate are soluble salts. Lead salts such as lead
arsenate have been used as insecticides, but their use in recent years
has been practically eliminated in favor of less harmful organic compounds.
Care must be used in handling lead as it is a cumulative poison. Environmental
concern with lead poisoning has resulted in a national program to eliminate
the lead in gasoline. Lead is priced at about $1/kg (99.9 %). |
| Use |
CONSTRUCTION MATERIAL FOR TANK LININGS, PIPING, EQUIPMENT
HANDLING CORROSIVE GASES & LIQUIDS USED IN MFR OF SULFURIC ACID, PETROLEUM
REFINING, HALOGENATION, SULFONATION, EXTRACTION, CONDENSATION; IN MFR OF
TETRAETHYLLEAD; FOR X-RAY & ATOMIC RADIATION PROTECTION; BEARING METAL
& ALLOYS; BUILDING CONSTRUCTION; METALLURGY; MFR OF PIGMENTS FOR PAINTS,
ORG & INORG LEAD CMPD, IN CERAMICS, PLASTICS, ELECTRONIC DEVICES.USED
IN WEIGHTS & AS BALLAST. COMPONENT OF LEAD OXIDE & ANTIMONIAL LEAD
STORAGE BATTERIES; CHEM INT FOR LEAD ALKYLS & PIGMENTS; PRODN OF AMMUNITION,
SOLDER, CABLE COVERING & SHEET LEAD; PRODN OF OTHER METAL PRODUCTS
(EG, BRASS, PIPES, CAULKING); OTHER USES (EG, BALLAST, PLATING, GALVANIZING
& ANNEALING) |
| Consumption Patterns |
Transportation-automotive batteries, gasoline additives,
70%; construction, ammunition, electrical uses, TV glass, and paint, 25%;
ceramics, type metal, ballast or weights, and tubes or containers, 5% (1986)
COMPONENT OF LEAD OXIDE BATTERIES, 36.5%; COMPONENT OF ANTIMONIAL LEAD
BATTERIES, 29.1%; CHEM INT FOR LEAD ALKYLS, 11.1%; CHEM INT FOR PIGMENTS,
5.7%; AMMUNITION, 4.1%; SOLDER, 2.6%; SHEET LEAD, 1.4%; CABLE COVERING,
1.4%; OTHER METAL PRODUCTS, 6.3%; OTHER, 1.8% (1982) Lead consumption in
the USA by product in approx metric tons for 1979: ammunition, 52,884;
bearing metal, 12,230; brass & bronze, 15,569; cable covering, 15,623;
caulking lead, 4,055; casting metals, 9,365; pipes, traps, bends, 2,942;
sheet lead, 6,545; solders, 40,429; storage battery grids, posts, etc,
309,838; storage battery oxides, 337,412; terne metal, 4,722; pigments,
82,788; antiknock additives, 186,947. Lead consumption in the USA by product
in approx metric tons for 1978: ammunition, 55,776; bearing metal, 9,510;
brass & bronze, 16,502; cable covering, 13,851; caulking lead, 9,909;
casting metals, 3,611; pipes, traps, bends, 10,479; sheet lead, 12,626;
solders, 68,391; storage battery grids, posts, etc, 412,568; storage battery
oxides, 466,714; terne metal, 3,778; pigments, 91,643; antiknock additives,
178,333. Lead consumption in the USA by product in approx metric tons for
1977: ammunition, 61,961; bearing metal, 10,873; brass & bronze, 15,148;
cable covering, 13,705; caulking lead, 8,725; casting metals, 5,428; pipes,
traps, bends, 10,555; sheet lead, 15,205; solders, 58,320; storage battery
grids, posts, etc, 416,709; storage battery oxides, 441,387; terne metal,
1,491; pigments, 90,703; antiknock additives, 211,295; annealing, weights,
galvanizing ballast, 21,478; other uses, 35,812. Lead consumption in the
USA by product in approx metric tons for 1976: ammunition, 66,659; bearing
metal, 11,851; brass & bronze, 14,207; cable covering, 14,452; caulking
lead, 11,317; casting metals, 6,085; pipes, traps, bends, 12,509; sheet
lead, 22,170; solders, 57,447; storage battery grids, posts, etc, 348,221;
storage battery oxides, 397,859; terne metal, 1,447; pigments, 95,792;
antiknock additives, 217,507; annealing, weights, galvanizing ballast,
24,401; other uses, 29,351. The Bureau of Mines is investigating a leach-electrolysis
technique to produce lead from galena concentrates without sulfur emissions.
The concentrate is leached with a hot FeCl3-NaCl solution to obtain a filtrate
containing more than 99% of the lead & a residue of elemental sulfur
& gangue material. Pure PbCl2 crystallizes out of the leach solution
on cooling & is electrolyzed in a relatively low temp fused-salt cell
to yield lead metal & chlorine gas. New developments in the refining
of lead in general have focused on improvements & adaptions of the
traditional pyrometallurgical & electrorefining processes, & esp
on the conversion of batch processes into continuous processes. Completely
continuous refining operations are the goal of these efforts. The recovery
of lead from scrap is an important source for the lead demands of the USA
& rest of the world. In the USA, 50% of the lead requirements are satisfied
by recycled lead products. The ratio of secondary to primary lead increases
with increasing lead consumption for batteries. The well-organized collecting
channels forecast a stable & growing future for lead. The principal
types of scrap are battery plates, drosses, skimmings, & industrial
scrap such as solders, babbitts, cable sheathing, etc. Some of this material
is reclaimed by kettle melting & refining. Most scrap is a combination
of metallic lead & its alloying constituents mixed with compounds of
these metals, usually oxides & sulfates. Most recycled lead derives
from scrap lead batteries since >50% of the lead consumed in the USA is
in the form of lead batteries. About 90% is reclaimed; hence, the bulk
of the recycling industry is centered on the processing of lead battery
scrap. At present, battery scrap is converted to impure lead or lead alloys
by pyrometallurgical processes employing blast, reverberatory, or rotary
furnaces. In many plants, a furnace combination is used. The overall recovery
of the metallic components of scrap in plants having both reverberatory
& blast furnaces is over 95%. The decisions being made by the operators
of secondary smelters as to which procedures will be designed into new
plants or installed in updating old plants are strongly influenced by the
introduction of new grid alloys, such as calcium alloys, low-antimony alloys
(2-3%), & strontium alloys, to replace the traditional 5-7% antimonial
alloys, & by air pollution standard requirements. The projected world
& USA demand for lead in the year 2000, including that supplied from
recycled lead, is est at approx 9X10+6 & 2.2X10+6 tonnage/yr, respectively.
This is an annual growth rate of about 3% for the world & 1.5% for
the USA. The demand in the developing nations is expected to grow at a
faster rate than in the industrialized nations. If these estimates are
correct, the lead industry in the USA would have to increase by 50 to 60%.
The cumulative demand for primary lead in the world from 1973 to 2000 has
been est at 140X10+6 tonnage. The est world reserves of 150X10+6 tonnage
are sufficient to supply this demand. The economics of USA lead prodn,
both primary & recycled, are markedly influenced by government regulations
concerning lead concn in air. Compliance with those standards has been
costly, & if more limiting standards are imposed, can result in a redn
of present smelter capacity & set limits on future expansion. |
| Apparent Color |
BLUISH-WHITE, SILVERY, GRAY METAL, LUSTROUS WHEN FRESHLY
CUT; CUBIC, CRYSTAL STRUCTURE |
| Odor |
Odorless |
| Boiling Point |
1740 DEG C |
| Melting Point |
327.4 DEG C |
| Molecular Weight |
207.20 |
| Density |
11.34 AT 20 DEG C/4 DEG C |
|
Chemical and
Physical Properties
|
VERY SOFT & MALLEABLE, EASILY MELTED, CAST, ROLLED,
EXTRUDED; DENSITY AT MELTING POINT: 10.65; RESISTIVITY (UOHM/CM) 20.65
AT 20 DEG C, 27.02 AT 100 DEG C, 54.76 AT 320 DEG C, & 96.74 AT 330
DEG C; THERMAL CONDUCTIVITY FROM 0.083 AT 50 DEG C TO 0.077 AT 225 DEG
C; 4 NATURAL ISOTOPES: 204 (1.4%), 206 (25.2%), 207 (21.7%), & 208
(51.7%); HEAT OF CAPACITY: 0.031 CAL/G @ 20 DEG C; HARDNESS 1 ON MOHS'S
SCALE; BRINELL HARDNESS (HIGH PURITY LEAD) 4.0; ATTACK BY PURE WATER, WEAK
ORGANIC ACIDS IN PRESENCE OF OXYGEN VAPOR PRESSURE: 10 MM HG AT 1162 DEG
C; 100 MM HG AT 1421 DEG C; 400 MM HG AT 1630 DEG C |
|
Environmental
Impact
|
METALLIC LEAD PRODUCED FROM ORE IS USED IN WIDE VARIETY
OF INDUSTRIES WERE IT IS CAST OR MOLDED INTO SHAPE & USED AS SOLDER.
THE DANGER COMES FROM SUBOXIDE WHICH MAKES A COATING ON SOLID LEAD &
FORMS DROSS ON THE SURFACE OF MOLTEN LEAD. THIS IS THE FORM OF LEAD FOUND
IN DUST OF CASTING ROOMS, PRINTING PLANTS, WHEREVER SOLID LEAD IS HANDLED,
& IN FUMES FROM MOLTEN LEAD. WHENEVER MOLTEN LEAD IS AGITATED SUBOXIDE
IS DETACHED & FLOATS UP WITH WAVES OF HEAT. THERE ARE 2 OCCUPATIONS
IN SHIPBUILDING WHICH CARRY HAZARD FROM LEAD SUBOXIDE--NAMELY, WELDING
& CUTTING METAL SHEETS WHICH CONTAIN LEAD OR ORE COVERED WITH RED LEAD
PAINT. HAZARD ALSO ARISES FROM USE OF VERY LARGE SPRAY GUNS TO APPLY LEADED
PAINT TO NEW STRUCTURES. MOST SEVERE HAZARD OCCURS IN SPRAYING OF MOLTEN
LEAD & LEAD PAINT GRINDING OR POWER SANDING SOLDER & POURING OF
LEADED IRON & STEEL MIXING ; WEIGHING OF LEAD POWDERS. PRINCIPAL TYPES
OF PRIMARY INDUSTRIES WITH OCCUPATIONAL EXPOSURE ARE LEAD MINING, SMELTING;
REFINING, STORAGE BATTERY MANUFACTURE, WELDING ; STEEL CUTTING & PRINTING.
HIGHEST EXPOSURES OCCUR IN SMELTING ; REFINING OF LEAD. MOLTEN LEAD &
LEAD ALLOYS ARE BROUGHT TO HIGH TEMP, RESULTING IN VAPORIZATION OF LEAD.
The exposure of humans to lead contamination in the environment, &
the ingestion of lead from cooking & eating utensils causes lead poisoning.
Acidic food, fruit juices, & wines stored in lead-lined bronze utensils
cause high lead toxicity among the Romans. Improperly glazed pots have
caused lead poisoning in recent times. Dietary exposure to lead ranges
from 100-500 ug/day, however people living near a smelter have intakes
of 670-2640 ug/day. The dietary intake, including water, for infants and
toddlers was 25 and 35 ug respectively for FY78. Stained glass workers
may be exposed to lead from soft solders. Exposures to lead dust may occur
during mining, smelting, and refining and to fume, during high temp (above
500 deg C) operations such as welding or spray coating of metals with molten
lead. There are numerous applications for lead compounds, some of the more
common being in the plates of electric batteries & accumulators, as
compounding agents in rubber mfr, as ingredients in paints, glazes, glass,
pigments, & in the chemical industry. It is est that approximately
783,000 industrial workers are potentially exposed to lead products. The
level of exposure resulting from contact is highly variable. Children with
pica for paint chips or for soil may experience elevation in blood lead
ranging from marginal to sufficiently great to cause clinical illness.
Certain adults may also be exposed to hazardous concn of lead in the workplace,
notably in lead smelters and storage battery manufacturing plants. Again
the range of exposure is highly variable. SEVERE MANIFESTATIONS, ESPECIALLY
ENCEPHALOPATHY, ARE PRACTICALLY NEVER ENCOUNTERED IN INDUSTRY OCCUPATIONS
IN WHICH LEAD POISONING IS INVOLVED INCLUDE THE USE OR HANDLING OF OR EXPOSURE
TO FUME, DUST OR VAPOR OF LEAD OR CMPD OF LEAD, OR SUBSTANCE CONTAINING
LEAD.STORAGE BATTERY MANUFACTURE HEADS THE LIST OF THE DANGEROUS LEAD TRADES
IN SOME COUNTRIES, ALTHOUGH THERE ARE NO RELIABLE STATISTICS, IT IS PROBABLY
ONE OF THE MOST PROLIFIC SOURCES OF PLUMBISM IN THE UNITED STATES. FORMERLY
USED IN COMPOUNDING RUBBER, & SOME OF THE SEVEREST CASES OF LEAD POISONING
REPORTED IN THE LITERATURE OCCURRED IN COMPOUNDERS & MIXERS OF RUBBER
WHEN LEAD WAS THE ACCELERATOR. People may be occupationally exposed to
metallic lead during smelting operations, battery manufacture, and the
production and handling of lead pipe, sheet, ammunition, solder, type metal,
and cable shielding. The lead industry employs about 7,000 people; two-thirds
of this number are employed in mining and concentrating operations. Air
concn in three primary lead smelters 80-2900 ug/cu m, mean; electric storage
battery manufacture 50-5400 ug/cu m, mean; welding and shipbuilding 180-2700
ug/cu m; printing 30-360 ug/cu m, tetraalkyl lead manufacture 120-179 ug/cu
m. Sources of lead in a child's environment include house dust (new inner-city
homes, 2 to 24 ug/sq ft floor surface; contaminated sources: old inner-city
homes, 33 to 486 ug/sq ft floor surface, mean 11,000 ug/g; homes of lead
smelter workers, mean 2,687 ug/g; homes within 1.6 km of smelter, mean
22,191 ug/g; & homes located 1.7 to 3.2 km from smelter, mean 2,124
ug/g). A cross-sectional study of blood lead levels in 100 inner city residents
of Stockholm for the period of 1980-1984 was conducted to investigate whether
recent measures undertaken in Sweden to decrease environmental exposure
to lead have had any effect. Measures include replacement of lead soldered
food cans and a decrease in allowable gasoline levels from 1.9 to 0.7 mmol
lead/l gasoline. The average blood lead levels of all the subjects examined
were 0.37, 0.26, and 0.25 umol/l for 1980, 1983, and 1984, respectively.
The mean change in individual levels between 1980 and 1984 was 0.12 umol/l,
which corresponds to an average individual decrease in blood lead of 34%.
The decrease occurred mainly during the period 1980-1983 (0.11 umol/l)
and was statistically significant for this period (p<0.01). Age, sex,
and change of residence during the observation period did not influence
the results. The body burden of the average adult in the USA is reported
to be not less than 100 mg and not more than 300 mg. Ninety-five percent
of the total body burden is stored in bone. THERE IS FAIRLY GOOD CORRELATION
BETWEEN DEGREE OF LEAD INTOXICATION ; BODY BURDEN OF LEAD, MAIN EXCEPTION
BEING WHERE THERE HAS BEEN HIGH EXPOSURE OVER SHORT PERIOD. Body burden
of lead increases from birth to old age. Total lead content in 60-70 year
old men may reach more than 200 mg with about 95% residing in the bone.
The mean lead level in the milk of occupationally unexposed women in Malaysia
was 43.5 ug/l. Human milk 12 ug/l and <5 ug/l in 2 studies. Blood lead
100-250 ug/l in occupationally unexposed rural and urban populations in
the majority of studies. Blood levels of German children 0-1 yr 33 ug/l,
6-8 yr 115 ug/l. Children aged 1-5 in rural U.S. counties 228 ug/l avg.
Urban children may display blood lead levels >590 ug/l. Blood levels in
children in a Texas city with smelter >400 ug/l. Human tissue from an industrial
city and rural area in northwest Germany 4.53 ppm avg and 2.74 ppm avg
respectively. Average blood levels in the EPA sponsored NHANES II survey
from Feb 1976 to Feb 1980 fell from 158 to 98 ug/l, during which time the
semiannual use of lead in gasoline dropped from 105 to 48 thousand tons.
Mean lead levels in whole blood and urine of subgroups of low income rural
black and urban Hispanics of Mexican-American ancestry ranged from 39.2-138.8
ug/l and 1.9-8,5 ug/l. Levels were highest for male rural blacks and lowest
from urban female Hispanics. Lead is also excreted in human milk in concentrations
up to 12 ug/l. Seventy-five workers in 27 radiator repair shops were interviewed
and tested for blood Pb and free erythrocyte protoporphyrin levels. Fifty-six
of the workers were actual radiator mechanics (repairing and soldering
radiators) and 19 workers performed other jobs, such as trucking and delivery.
No totally unexposed controls were tested. The mean blood Pb level found
in the radiator mechanics was 37.1 +/- 13.8 ug/dl (range 16-73 ug/dl),
(39% had blood Pb levels >40 ug/dl and 16% had levels >50 ug/dl). The mean
blood Pb level for the other workers was 21.6 +/- 11.2 ug/dl (range 7-51
ug/dl). Multiple regression analysis showed that the most significant variable
contributing to an increase in the blood Pb level was the number of radiator
repair stations within the shop. Mean zinc protoporphyrin levels (used
as a screen for lead intoxication) was 40.6 ug/dl for the radiator mechanics
and 15.6 ug/dl for the other workers. One 32 yr-old radiator mechanic whose
Pb level was 72 ug/dl, reported with symptoms of fatigue, headache, dizziness,
nausea, and abdominal and back pains. A group of 109 male workers occupationally
exposed to both antimony (as Sb2O3) and lead in the glass-producing industry
were examined for levels of these metals in whole blood and urine. The
workers were divided into four groups based on specific work activities:
melter (n= 32), batch mixer (n= 45), craftsman (n= 8), and glass washer
(n= 24). Blood and urine samples were collected at the end of a shift.
Concentrations of lead in the blood ranged from 70 to 680 ug/l. Median
values for melters, batch mixers, craftsmen, and glass washers were 220,
340, 275, and 170 ug/l, respectively. A significant difference (p< 0.05)
was found only between the batch mixers and glass washers. The urinary
lead values ranged from 7 to 110 ug/l with median values for melters, batch
mixers, craftsmen, and glass washers of 35, 43, 24, and 42 ug/l, respectively.
A significant difference was found between only the batch mixers and craftsmen
(p< 0.05). Exposure rates for lead were not given. |
|
Environmental Fate
|
EXTENT OF OCCURRENCE IN EARTH'S CRUST IS ABOUT 15 G/TON,
ALSO EXPRESSED AS 0.002% (DEPTH OF CRUST: 16 KM). OCCURS CHIEFLY AS SULFIDE
IN GALENA, OTHER MINERALS WHICH CONTAIN LEAD CMPD INCLUDE ANGLESITE , CERUSSITE,
MIMETITE,and PYROMORPHITE .LEAD RARELY OCCURS IN THE ELEMENTAL STATE, BUT
EXISTS IN A NUMBER OF ORES ALSO OCCURS IN VARIOUS URANIUM THORIUM MINERALS,
ARISING FROM RADIOACTIVE DECAY. Sources contributing to airborne lead are
silicate dusts, volcanic halogen aerosols, forest fires, sea salt aerosols,
meteoric and meteoritic smoke, and Pb derived from the decay of radon.
Lead enters the environment from lead-bearing minerals. The median lead
concentration in the soil (to a depth of 20 cm) is 15-16 ug Pb/g soil with
95% of samples being <30 ppm. It is estimated that 10X10+9 kg of lead
is produced in volcanic dust with an average concn of 640 ppm. Through
erosion and leaching, lead may be transferred from the soil into surface
waters and the atmosphere. However calculations indicate that the contribution
of these natural sources to lead in the atmosphere is relatively small.
The amount of lead that enters the ocean from river discharges from natural
sources has been set at 17000 tons annually, also a relatively small contribution
to lead in the aqueous environment. The form of lead is generally unspecified.
Metallic lead is naturally occuring and is the end product of three natural
radioactive elements uranium (206), thorium (208), and actinium (207).
During 1973-4 NIOSH conducted environmental surveys of 9 indoor firing
ranges. Several sources of lead dust and fume generation were found; one,
from the bullet primer, produced 25-30 mg of lead styphnate and lead peroxide.
Another source is lead vaporization, resulting from the 2000 deg F temperature
generated upon firing and fragmentation of the lead bullet. Of a total
of 331 samples for airborne inorganic lead concentrations of lead range
from 0.10 to 13.17 mg/cu m for general air samples, and from 0.01 to 34.50
mg/cu m for personal samples. Investigators concluded that indoor firing
ranges constitute "present health hazards from lead poisoning" (due to
improper ventilation control). Ceramic artists can be exposed to many hazardous
materials, generally related to dry clays, glazes and kiln use. Glazes
can contain lead, antimony, arsenic, barium, beryllium, boron, chromium,
cobalt, cadmium, copper, vanadium and other materials which all have potential
toxic effects. Electric arc welding produced an average concn of 5.63 mg/cu
m and oxy-acetylene welding produced 1.96 mg/cu m of lead. Lead is emitted
from various types of melting furnaces (basic oxygen, open hearth, and
electric) in the steel and grey iron (cupola and electric) industries.
Mining, smelting, and refining as well as the manufacture of lead containing
cmpd and goods, give rise to lead pollution. Lead (Pb) emissions from stacks
and slag heaps of primary and secondary Pb smelters. /Inorganic lead/ Coal
fired power plants, ceramic manufacturing, and mine seepage. Lead is the
fifth most important metal in the USA economy in terms of consumption.
Of this approximately 85% of the primary lead is produced domestically
and 40-50% is recovered and recycled(1). Eighty eight percent of the lead
mined in the US comes from seven mines in the New Lead Belt in southeastern
Missouri; the rest coming from eight mines in Colorado, Idaho, and Utah.
Three of the six USA lead smelters are from this region, the others are
located in Idaho, Montana, and Texas(2). Metallic lead is produced by smelting
ore concentrates or scrap metal; lead or its compounds can enter the environment
during its mining, ore processing, smelting, refining, use, recycling or
disposal. In the USA in 1984, 71.7% of the 1.2 million metric tons of lead
metal consumed was used for batteries, 6.5% was used as an intermediate
for gasoline antiknock additives, 6.4% for pigments and ceramics, 4.0%
for ammunition, 2.0% for solder, 1.0% for cable covering, 0.3% for caulking,
2.3% for pipe and sheet, 0.18% for type metal, 0.6% for brass and bronze,
0.4% for bearings, 4.6% for miscellaneous uses. Estimates of lead dispersal
into the environment indicate that the atmosphere is the major initial
recipient. Of the 39 million tons of estimated total US emissions in 1984,
the estimated allocation between sources is (source category, %): gasoline
combustion, 89.4; waste oil combustion 2.0; solid waste disposal 0.9; coal
combustion 0.7; oil combustion, 0.3; gray iron production, 0.1; iron and
steel production, 1.1; secondary lead smelting, 0.7; primary copper smelting,
0.1; ore crushing and grinding, 0.3; primary lead smelting, 2.8; zinc smelting,
0.3; other metallurgical, 0.1; lead alkyl manufacturing, 0.6; lead acid
battery manufacture, 0.3; portland cement production, 0.2; miscellaneous,
0.1. The form of lead released into the environment during the production
and use of elemental lead is generally not reported in monitoring studies.
However the chemical composition of baghouse effluent from smelting and
refining operations has been examined in one study which found that elemental
Pb composed 15-20% of the emissions in some cases; with PbS, PbSO4, and
PbO.PbSO4 also being present. The median particle size of Pb emissions
was 1.5 um with a geometric standard deviation of 5 um. Because 86% of
lead-containing aerosols are <10 mu distribution, their fallout rate
is low and long-range transport should occur. In addition to air emissions
from smelters and refineries, lead may also be discharged in wastewater
and runoff from production and use facilities. An analysis of sediment
cores of lakes in Ontario and Quebec that are remote from point sources
of Pb indicate that the lead burden is primarily due to long-term atmospheric
deposition beginning around 1850. The deposition is highest in South-Central
Ontario where the lake burdens ranged from 312-432 mg/sq m and decreased
in an eastward direction and to the north where the lowest deposition occurred,
31-42 mg/sq m. Because of its good corrosion resistance, the use of metallic
lead should not lead to large release of lead into the environment. However,
some dissolution occurs from lead water pipe or soldered cans especially
where the water is soft or acidic. Wear of lead-containing components will
also contribute to lead releases(SRC). Lead producing industry (est releases
to the environment): primary lead: 893 ton/yr (atmosphere), 200-500 ton/yr
(waste water), 21,000 ton/yr (land); secondary lead: 750 ton/yr (atmosphere),
3,260 ton/yr (land); secondary brass and bronze: 47 ton/yr (atmosphere),
10 ton/yr (waste water), 460 ton/yr (land). Lead consuming industries (est
releases to the environment): battery manufacture: 82 ton/yr (atmosphere),
1-340 ton/yr (waste water), 40 ton/yr (land) lead alkyl manufacture: 1000
ton/yr (atmosphere), 60 ton/yr (waste water); lead oxides and pigments:
112 ton/yr (atmosphere), 200 ton/yr (land); lead stabilizers: 40 ton/yr
(atmosphere), 40 ton/yr (land); cable covering: 113 ton/yr (atmosphere);
type metal: 435 ton/yr (atmosphere); can soldering: 60 ton/yr (atmosphere);
ceramics: 600 ton/yr (atmosphere). Indirect sources (est releases of lead
to the environment); gasoline distribution: 420 ton/yr (atmosphere); gasoline
combustion: 122,000 ton/yr (atmosphere); waste oil disposal: 3,400 ton/yr
(atmosphere), 4,600 ton/yr (land); coal combustion: 225 ton/yr (atmosphere),
4,275 ton/yr (land); oil combustion: 100 ton/yr (atmosphere); cement manufacture:
312 ton/yr (atmosphere); iron and steel manufacture: 605 ton/yr (atmosphere);
grey iron products: 1,080 ton/yr (atmosphere); ferro alloy production;
30 ton/yr; solid waste incineration: 1,170 ton/yr (atmosphere); sludge
disposal: 5 ton/yr (atmosphere), 2,400 ton/yr (land). Lead is a extremely
stable metal, although it dissolves in acid. While some corrosion may be
expected in soil, generally an inert coat of an insoluble salt will form
and limit further corrosion. It is expected to convert to more insoluble
forms such as PbSO4, Pb3(PO4)2, PbS, and PbO. It also forms complexes with
organic matter and clay minerals that limits its mobility. Concentrations
of Pb in soil solution reach a minimum between pH 5 and 6 and increase
below pH 4 to 5 and above pH 6 to 7, because metal-organic complexes form
in this pH range. Only a small fraction of lead in lead contaminated soil
appears to be in water-soluble form, 0.2-1% according to one report, although
the fraction soluble in EDTA ranged from 43-67% of the total lead in soil.
The EDTA extractable material should include largely the chelated metal
ions held in the soil organic and organomineral complexes although there
is some evidence that the metal adsorbed on colloidal surfaces such as
insoluble inorganic compounds may also be extracted. When 500 ppm Pb was
added to soil as the soluble chloride, it became insoluble within an hour
of contact with the soil, this insolubility lasted the duration of a 42-day
experiment. After 42 days 0.7 and 70% were in the water-soluble and EDTA-soluble
fractions, respectively. The percentage of lead in the water-soluble and
EDTA-extractable fraction was similar when the insoluble PbO oxide was
added to soil rather than the soluble chloride. If released into water,
metallic lead will simply sink into the sediment. Surface layers of insoluble
salts may form and protect the surface from further corrosion. In the dissolved
state, it will form ligands, the dominant ones varying with pH. In freshwater
systems, the most important ligands are HCO3, CO3, OH and (OH)2, whereas
in seawater they are Cl, CO3, (OH), (OH)2, Cl2, and Cl3. A characteristic
of lead is its tendency to form compounds of low solubility with the major
anions of natural water. As a result natural concentrations of lead in
lead-ore deposits do not move appreciably in ground or surface water but
rather any dissolved lead will tend to combine with carbonate or sulfate
ions to form insoluble lead carbonates or sulfates or be absorbed by ferric
hydroxide. Precipitation has been shown to be important, at relatively
high pH. The amount of lead that can remain in solution in water is a function
of the pH of the water and the dissolved salt content which is about 30
ug/l in hard water (pH > 5.4) and about 500 ug/l in soft water (pH <5.4).
Much of the lead carried by river water is in the form of suspended solids.
One study of the distribution of lead between filtrate and solids in stream
water from urban and rural areas reported the ratio of lead in suspended
solids to that in filtrate varied from 4% in rural areas to 27% in urban
areas. Sorption also appears to be an important process in removing lead
from both fresh and estuarine natural waters into sediment. The amount
adsorbed depends on parameters such as the availability of ligands, pH,
redox conditions, salinity, iron concentration, composition of dissolved
particulate matter and sediment, and lead concentration. Lead is adsorbed
by polar particulate matter as is evidenced by its dominance in sediment
of specific gravity 2.0-2.9, where the clay fraction is found. It is almost
absent from less dense sediment, characterized by organic matter not active
in complex formation or denser fractions, characterized by precipitation.
Another study showed that the organic content of the bottom mud was the
most significant factor affecting adsorptivity. Biomethylation of lead
by benthic microorganisms can lead to its remobilization and reintroduction
into the aqueous environment compartment. In a 38-day intertidal benthic
mesocosm experiment in which there were daily additions of lead to a caisson
containing sediment, seawater and fauna placed on an intertidal sand flat
in the German Bight, the lead equally distributes between the dissolved
and particulate matter in the water column during high tide with the levels
decreasing during ebb tide due to exchange with the sediment, porewater
and infauna. The lead accumulated primarily in the uppermost cm of sediment.
Cycling of Pb in estuaries involves a complex exchange between dissolved
and particulate phases. Particulate speciation studies of Pb flowing from
a French river to the sea showed that the carbonate-bound and exchangeable
Pb decreased while bound Fe- Mn oxides and organic Pb increased. Mobilization
of Pb occurred in the lower estuary where particles are depleted in Pb,
transported above the salt intrusion and recycled to the tidal estuary
by tidal currents. When lead sulfide in sewage effluent is discharged into
seawater, the lead will be diluted and oxidized leading to the dissolution
of the sulfide solid. Due to its very low vapor pressure
and insolubility, volatilization of lead from soil or water will be negligible.
However relatively volatile tetramethyllead can be formed in anaerobic
lake sediment and loss of lead via volatilization can subsequently occur.Due
to its very low vapor pressure and insolubility, volatilization of lead
from soil or water will be negligible. However relatively volatile tetramethyllead
can be formed in anaerobic lake sediment and loss of lead via volatilization
can subsequently occur Background 0.5 ppb; estimate of global mean lead
content of lakes and rivers 1-10 ppb; Canadian lakes 39-103 ppb, U.S. lakes
6-34 ppb. Particulate fraction of fresh water in USA northwest coast is
66 ppb. Lake Huron and Georgian Bay 0.022 ppb, median). Mean dissolved
Pb concns at 5 sites in the Pb/Ag mining district of mid-Wales 0.008-0.58
ppm. In a 1970 study of dissolved lead in 726 rivers and lakes in the USA
and Puerto Rico, 63% of the samples had levels in excess of the detection
limit, 1 ppb, but only 3 samples exceeded 50 ppb. Positive samples were
concentrated in the northeast and southest sections of the country where
the water composition is thought to be favorable for solution of lead.
9% of samples taken from the lower Mississippi River between 1978 to mid-1983
(435 samples) had Pb levels exceeding 50 ppb with 5 greater than 500 ppb
and one exceeding 10000 ppb. High level occurred in acute episodes that
appear to be associated with human activity and occurred at Luling (river
mile 1200) and Belle Chasse (river mile 75). The fact that these high concentrations
do not persist downstream suggests that mechanisms of dilution or immobilization
are at work. Coastal seawater 0.08-0.4 ppb, Central Atlantic water 0.05
ppb avg; Bering Sea 0.03-0.68 ppb. Seawater below 1000 m in the Pacific
and Atlantic Oceans and Mediterranean Sea 0.03-0.04 ppb. The particulate
fraction of seawater along the northwest coast of the U.S. 56 ppb. Seawater
off Southern California 0.04 ppb. Antarctic snow before 1940 <0.001
ppb, recently 0.2 ppb. Glacial ice around 1870 from Norway and Poland 5.86
and 5.0 ppb avg respectively while today the mean levels are 9.88 and 148
ppb respectively . Pb in fresh snow particulate matter in Toronto was 140
ppb, mean while at four other sites in Ontario it ranged from 42-80 ppb.
Palo Alto - freeway 0.181 ppb, residential 0.149 ppb, foothills 0.035 ppb.
Mean levels of Pb in rural and remote precipitation reported in the literature
are 3.0-15 ppb and <0.04-2.39 ppb, respectively. A study was conducted
on the distribution of manganese, iron, copper, lead, and zinc in the water
and sediment of Kelang esturary in 1981. The mean total levels of manganese,
iron, copper, lead, and zinc in the estuarine water were 27.1 ug/l, 106.5
g/l, 10.0 ug/l, 4.1 ug/l and 17.9 ug/l respectively. The results indicate
that Kelang estuary is polluted with lead, manganese, and iron. However,
levels of these heavy metals may still be considered safe for aquaculture,
if the farm is located at least 10 km away from the river mouth. Due to
its very low vapor pressure and insolubility, volatilization of lead from
soil or water will be negligible. However relatively volatile tetramethyllead
can be formed in anaerobic lake sediment and loss of lead via volatilization
can subsequently occur Big River (Old Lead Belt, MO) sediment and organic
detritus contain 1400-2200 and 800-7000 ppm of lead, respectively. Soil
samples collected 0.3 km from an industrial park containing a battery manufacturing
plant and a Missouri ore processing plant contained elevated Pb levels
945 and 983 ppm, mean 0-5 cm depth, and 257 and 204, mean 5-15 cm depth,
in 1982 and 1983, respectively. The extractable Pb levels were 117 and
1 ppm, mean 0-5 cm depth, and 36 ppm and not detected mean 5-15 cm depth
in 1982 and 1983, respectively. The battery manufacturing plant closed
after testing in 1982, suggesting that the extractable Pb in these soils
reflected recent additions and that reversion to nonextractible forms were
rapid. All other sites tested had essentially the same Pb levels, 47-106
ppm, and <1 ppm or non detectible amounts of extractable Pb in 1983.
Soil and dust sampling downwind of battery manufacturing and secondary
smelter/battery manufacturing plants in Houston indicate that the smelters,
but not the battery manufacturing facilities result in significantly elevated
Pb levels that correlated with distance. Soil lead levels near battery
manufacturing plants are slightly elevated compared with reference areas.
Mean lead concn in peat soil and sediment from the Pungo River peatland
area of coastal North Carolina: surface soil 12.8 ppm, soil (20 cm depth)
2.7 ppm, soil (1 m depth) 3.6 ppm, surface sediment 0.1 - 7.0 ppm. Most
of the lead is associated with the residual fraction with less amounts
organically bound and negligible amounts in the water-soluble fraction.
Concns of lead in a polluted sediment in the Rhine River near Mainz ranged
from 32 ppb to 4 ppm and are primarily bound to organic matter in an extremely
reducing environment. In polluted and unpolluted estuarine sediment in
England 18-22% of the lead is organically bound, 4-11% is easily leachable
and exchangeable, <4% tied up with hydroxides or possibly carbonates,
and the remainder resistant (possibly derived from rock). Mean lead levels
in West Midlands England soil for four land-use types were: agricultural
49 ppm, suburban/residential 109 ppm, mixed industrial/residental 140 ppm,
industrial/inner urban 260 ppm. 10 mg/l lead found in illicitly distilled
whiskey. As a general rule, foods which are apt to have elevated lead concentrations
are dried foods, liver, canned food, and vegetable that have a high area
to mass ratio. The effect of soldered cans on the lead concentration in
food is illustrated by the fact that the mean lead content of ravioli in
a 98% Pb/2% Sn soldered can was 150 ppb while the same food in a welded
(no lead) can was 30 ppb. Condiments 0-1.5 ppm; fish and seafood 0.2-2.5
ppm; meats and eggs 0-0.37 ppm; grains 0-1.39 ppm; vegetables 0-1.3 ppm;
wine 60-255 ppb, 130-190 ppb avg. Another value for wine of 299 ppb, avg
has been reported. Moonshine whiskey commonly exceeds 10 ppm. Lead in canned
food: fruit 0.01-14.0 ppm, fruit juice 0.01-3.1 ppm, vegetables 0.01-38.6
ppm, tunafish 0.08 ppm avg. Dietary exposure to lead ranges from 100-500
ug/day, however people living near a smelter have intakes of 670-2640 ug/day.
Results for the FDA's Total Diet Study including data for adult diet market
basket samples collected from Oct 1977 through Sept 1978 in 20 cities throughout
4 geographical areas (240 composites): 64% had residues of lead ranging
from 0.01-0.40 ppm contributing to a daily intake of 79.3 and 95.1 ug of
lead in FY77 and FY78 respectively. Lead was found in all 12 food classes
including: dairy products 0.01-0.20 ppm, 0.014 ppm avg; meat fish and poultry
0.02-0.10 ppm, 0.031 ppm avg; grain and cereal products 0.02-0.18 ppm,
0.055 ppm avg; potatoes 0.01-0.29 ppm, 0.046 ppm avg; leafy vegetables
0.01-0.08 ppm, 0.020 ppm avg; legume vegetables 0.05-0.40 ppm, 0.162 ppm
avg; root vegetables 0.02-0.11 ppm, 0.027 ppm avg; garden fruit 0.03-0.34
ppm, 0.089 ppm avg; fruits 0.02-0.21 ppm, 0.045 ppm avg; oils, fats, and
shortening 0.02-0.16 ppm, 0.020 ppm avg; sugar and adjuncts 0.02-0.15 ppm,
0.051 ppm avg; beverages 0.02-0.08 ppm, 0.018 ppm avg. Lead was found in
52% and 58% of the 98 and 110 composites sampled in the infant and toddler
total diet study respectively, with lead concentrations ranging from 0.003-0.51
ppm. The dietary intake, including water, for infants and toddlers was
25 and 35 ug respectively for FY78. Lead is frequently found as an impurity
in calcium nutritional supplements derived from limestone and dolomite(SRC).
This lead is probably in the form of lead sulfide since lead deposits of
the "replacement type" are deposited in susceptible sedimentary rock, usually
limestone and dolomite. Natural constituent in all plants with normal concentration
in leaves and twigs of woody plants 2.5 ppm, pasture grass 1.0 ppm; cereals
0.1-1.0 ppm. Some trees have the capacity to accumulate large amounts of
lead from contaminated soil - the tips of larch, pine, and fir contained
100 ppm lead when grown in lead mining areas with soil concentration appreciablly
different from the usual concentration (80,000 ppm) in most soils. However,
in most cases this indicates that there is no significant bioconcentration
of lead from soil into plants. Lead on leafy parts of plants result from
deposition of Pb from air. An experiment performed with hydroponically
grown corn showed that lead was taken up and precipitates in the cell walls.
Aquatic plants from the Chesapeake Bay region 2.2-18.9 ppm dry weight.
Aquatic bryophytes from the Pb/Ag mining district of mid-Wales contained
34-49,400 ppm dry weight which correlated well with the concn of dissolved
Pb in the streams. Concn of lead in freshwater fish 0.16-0.24 mg/kg, with
12 mg/kg in liver, 5.7 mg/kg in gills and 1.4 ppm in muscle. Lead was found
in the soft tissue of freshwater mussels in the Thames River, with mean
concn ranging from 9.8-42.5 mg/kg (dry weight). The higher concentrations
were found in mussels taken from urban sites. Shellfish in general have
been reported to contain 0.31 mg/kg, soft shell clam an avg of 0.7 mg/kg
& northern quahog clam an avg of 0.52 mg/kg lead on a wet wt basis.
Oysters have been found to contain 0.47 mg/kg. Fresh tuna fish muscle was
reported to contain 0.3 mg/kg lead. As part of the National Contaminant
Biomonitoring Program, freshwater fish were collected from 112 stations
located throughout the US. The geometric mean and range of Pb in 1978-79
(ppm wet weight) was 0.19, 0.10-6.73 and for 1980-81 was 0.17, 0.10-1.94(1).
The specimen with the highest Pb concn in 1978-79 came from a stream near
Honolulu, HA; no specimens were analyzed from this station in 1980-81(1).
In the Big River, MO (inactive Old Lead Belt), average lead levels in edible
tissue in 3 species of suckers at 9 stations (157 samples) ranged from
0.13 to 0.88 ppm wet weight compared with 0.06-0.12 at a background station.
61% of these fish had levels in excess of the 0.3 ppm standard and the
highest concentration measured was 1.30 ppm, from a site below a ruptured
tailings pond dam. Average values in sunfish and smallmouth bass ranged
from not detected to 0.39 ppm. Mean lead concentrations of fish from streams
in the New Lead Belt (71 samples) and the defunct Tri-State Mining District
(100 samples) ranged from 0.03 to 0.4 ppm and 0.03-0.11 ppm, respectively.
Mean controls in these two regions ranged from not detected to 0.04 ppm.
The normal pH and hardness of all streams sampled was 7.0-8.4 and 100-300
mg/l CaCO3. Lead concn in clams (R cuneata) from the Pungo River peatland
area of coastal North Carolina contained 0.2-0.5 ppm dry weight Pb. Clams
from the Chesapeake Bay region contained 0.8-20.4 ppm dry weight Pb. Principal
source of exposure to ducks and waterfowl is from lead shot which is ingested
by the birds in search of gravel. Livers of 28 species of birds with no
known lead exposure 0.3-7 ppm. Small mammals within 10 m of road 2.6-15.2
ppm with the contents higher along high traffic road and among insectivores;
urban biota 11-367 ppm, rural biota 4.7-16 ppm. Riparian wildlife from
sites in the active New Lead Belt mining district of southeastern Missouri
(species - geometric mean in ppm wet weight (range in ppm)): Bullfrog carcasses
- 1.22-1.47 (not detected - 7.40), Northern water snake carcasses 0.15-1.21
(not detected - 3.90), Rough-winged swallow carcasses - 0.23-2.39 (not
detected - 61.2), Muskrat livers - 0.07-0.26 (not detected - 0.53). Data
from the Old Lead Belt mining district in southeastern Missouri (species-geometric
mean in ppm wet weight (range in ppm) Bullfrog carcasses - 12.6-109.0 (2.90-300.0),
Northern water snake carcasses 0.15-1.21 (not detected - 3.90), Rough-winged
swallow carcasses - 0.44-1.86 (not detected - 14.7), Muskrat livers - 0.64-0.69
(0.29-1.60). Site upstream from the old lead belt: Bullfrog carcasses -
0.97 (0.11-6.10), Northern water snake carcasses 6.07- 7.52 (1.60-14.1),
Rough-winged swallow carcasses - 0.51 (not detected - 5.40), Muskrat livers
- 0.16 (not detected - 0.32). While mining in the Old Lead Belt ceased
in 1972, this district contains huge tailing piles from which lead enters
the river by erosion and seepage. Herring gulls feeding on refuge from
a dump receiving large quantities of industrial residues from leather,
ceramics, and glass manufacturing in addition to domestic refuge contained
an average of 13.25 ppm of Pb in their kidneys compared with <0.10 to
3.78 ppm for gulls feeding from 3 other dumps. Milk directly from cows
9 ppb; whole bulk milk 40 ppb avg; local milk from U.S. markets 20-40 ppb;
canned milk 0.05-0.2 ppm. Results of a 1982 survey of lead in Canadian
milk (68 samples) ranged from 0.01-2.48 ppb, 1.12 ppb, mean, 1.19 ppb median.
Canned evaporated milk and infant formula ranged from 27-106 and 1.1-122
ppb, respectively. The mean lead level in the breast milk of occupationally
unexposed women in Malaysia was 43.5 ug/l. Human milk in two previous studies
contained 12 ug/l and <5 ug/l. Lead is also excreted in human milk in
concentrations up to 12 ug/l. Traces of lead occur in many rocks in addition
to those that qualify as ores. It thus finds its way into soil & water
& hence into food & into human & animal tissues even in remote
places where there is no use of the metal or its compounds. Heavy metals
such as lead, arsenic, antimony, cadmium, chromium, cobalt, manganese,
and mercury used as color pigments in paints can be ingested by contamination
of hands, fingernails, food, cups, cigarettes and by holding paint brushes
in the mouth. The principal route of exposure is food, but it is usually
environmental & presumably controllable sources that produce excess
exposure These sources include lead in air from combustion of lead-containing
auto exhausts or industrial emissions, lead-based paint, hand-to-mouth
activities of young children living in polluted environments, &, less
commonly, lead dust brought home by industrial workers on their clothes
& shoes, & lead-glazed earthen ware. Lead is dissolved out of lead
water supply pipes to enter the diet through the drinking water. The disposal
of metallic lead & demolition debris in landfills therefore poses a
potential hazard if the leachate is allowed to pass into ground water feeding
a water supply system. Eating of lead paint by children and drinking of
lead contaminated, distilled (moonshine) whiskey are important sources
of non industrial poisoning. Exposure to burning battery castings, drinking
of liquids from improperly fired, lead glazed containers, and high levels
of airborne lead. Poor work hygiene, smoking during work (pollution of
tobacco; polluted fingers while smoking), poor personal hygiene may considerably
increase total exposure mainly by the oral route. Ingestion of dust, inhalation
of dust or fume, skin and eye contact. Man absorbs lead in small amounts,
which normally does not cause poisoning, from food, water, and air. People
living in the vicinity of lead mining operations, processing, and use operations
may be exposed to lead principally by ingesting dust, although the form
of lead ingested is not usually known. While solubility of metallic lead
is low and adsorption through the lungs is slight, some lead may be solubilized
in the stomach after which it may be absorbed in moderate quantities. The
general population is exposed to lead in the air which arises from the
use of leaded gasoline and industrial sources. This lead is primarily in
airborne particulate matter that settles out on plants and in water and
may subsequently be ingested. Lead in drinking water most frequently arises
in soft water areas where the water distribution system contains lead pipe,
however the water supply itself may contain lead from natural sources,
fallout or runoff. Lead may also leak into tap water from PVC as well as
leaded pipes where lead stearate is used as a stabilizer in the pipe. Lead
concentrations in canned food vary widely but they average about ten times
greater than fresh food. Another source of dietary lead is from the use
of inadequately glazed earthenware vessels for food storage and cooking.
Exposure may arise from contact with clothing from occupationally exposed
people, drinking whiskey made in home-made stills containing lead and contact
with lead storage batteries. Children are exposed to lead from ingesting
lead paint, colored newsprint or playing in the dirt especially near busy
highways. |
|
Drinking Water
Impact
|
A survey of lead in Canadian drinking water 7.8% <1.0
ppb, 89% 1.0-29.9 ppb and 3.3% >30 ppb. Tap water from 969 U.S. water supplies
- 1.4% >50 ppb with systems having soft water and pH <6.5 particularly
high. In a comparison of finished and tap water in 2 U.S. cities in which
the water was slightly acidic and chlorination was the only treatment,
the majority of tap-water samples contained >50 ppb lead with a range of
13 to 1510 ppb and an average of 30 ppb; in all 383 households the lead
concentration was higher at the tap than at the treatment plant showing
that lead was picked up in the distribution system. Lead increases in water
that remain in the distribution system overnight. In a Nova Scotia study
the mean Pb concn in standing water was 43 ppb, a factor of 5 to 22 above
that of running water. |
|
Disposal
|
At the time of review, criteria for land treatment or
burial (sanitary landfill) disposal practices are subject to significant
revision. Prior to implementing land disposal of waste residue (including
waste sludge), consult with environmental regulatory agencies for guidance
on acceptable disposal practices. Precipitation is the preferred treatment
process for removing toxic heavy metals from electroplating waters. Precipitation
processes include hydroxide, lime and/or sulfide treatment. Chemical reduction
is used to treat complex metals such as nickel, copper, hexavalent chromium
waste, soluble lead, silver, metal containing cyanide, and mercury. Adsorption
has shown potential for treating and polishing aqueous metal bearing wastes.
Activated carbon, activated alumina, and iron filings are all applicable
adsorbents. Alkaline chlorination and incineration are effective cyanide
destruction treatments. Evaporation, ion-exchange, reverse osmosis, electrodialysis,
and electrolytic recovery are waste reduction and recovery techniques applicable
to metal bearing hazardous streams. |
|
Atmosphere
|
Lead released to the atmosphere will be in particulate
matter and be subject to washout and gravitational settling. Transformations
in the atmosphere to the carbonate and oxide may be expected. Estimates
of the annual net Pb deposition to the tropical North Pacific Ocean is
2.0 and 5.0 ng/sq cm, respectively and is predominately from noncrustal
sources. Recycled sea spray represents a significant but variable component
of the deposition. The average annual scavenging ratio (concn in precipitation
(mg/l) to air concn (ug/cu m)) for Pb is 0.18X10+6, the lowest value of
the 7 trace metals studied. The mean ratio of wet to dry deposition of
lead in southern, central and northern Ontario is 1.63, 1.99, and 2.50,
respectively. 0.1-1ng/cu m. RURAL: 0.1 ug/cu m avg; <0.5 ug/cu m; 7
rural sites in the UK 0.033-0.245 ug/cu m, suspended particles in rural
air samples <0.01 to 1.4 ug/cu m, 0.2 ug/cu m avg. National Air Surveillance
Network mean (max) nonurban Pb concns for 1977, 1978, 1979 0.0920 (0.1035),
0.0843 (0.1100), 0.0842 (0.1019) ng/cu m, respectively. Lead typically
occurs in suspended particulates equal or <0.5 um at annual avg concentration
of < 0.1 to 5 ug/cu m, 1-2 ug/cu m avg. 6 U.S. cities organic lead 0.2-0.3
ug/cu m avg in air, particulate lead 1.2 - 5.1 ug/cu m. Lead concentration
in air decreases with distance from urban center with urban concentration
being 1.1 ug/cu m and suburban 0.21 ug/cu m. National Air Surveillance
Network mean (max) urban Pb concns for 1977, 1978, 1979 0.889 (7.48), 0.765
(8.41), 0.584 (9.68) ng/cu m, respectively. Downtown Los Angeles 4-5 ug/cu
m of lead, the highest for samples collected at 92 urban and 16 non-urban
sites in the US between 1965 and 1974; concentration decreased after 1971
which is attributed to reduced lead in gasoline. The organic component
of airborne lead collected during a 3 day period was 6%, 4-12% and 17%
of the total airborne lead in Pasadena, Fort Collins and in an underground
garage respectively. Twelve month air monitoring (1968-71) of 6 US cities
(8763 samples) (city - geometric mean concn (ug/cu m): Chicago - 1.44,
Cincinnati - 1.45, Houston - 1.14, Los Alamos - 0.17, Los Angeles - 3.40,
New York - 1.40, Okeana, OH - 0.30, Phildelphia - 1.53, Washington, DC
- 1.36(4). Daily samples collected in the vicinity of a primary smelter
in El Paso, TX between February and June 1972 averaged 6.6 ug/cu m but
fell off rapidly with distance. Indoor concentration are quite variable,
but are generally one- to two-thirds the concentration of adjacent outdoor
levels. Values ranged from 0.18 to 0.34 ug/cu m., 0.28 ug/cu m in 239 samples
from 12 homes. The lead concentration in the air of an indoor shooting
range was 400 ug/cu m before firing began, and ranged from 1710-34900 ug/cu
m on the firing line, 2170-34900 ug/cu m at the target and 4430-10500 ug/cu
m at midrange. Outdoor ambient air levels ranged from 0.13-0.69 ug/cu m. |
