Lead - Toxicology of Metals - page 586

than the standard) and reported in the publications
(not to skew the distribution). Also, the original num-
bers of decimals for effect estimates have been kept,
despite the sometimes large uncertainties.

lead in paint, soil, and other environmental samples
( Kuruvilla et al ., 2004), over anodic stripping voltam-
metry (ASV) instruments for determination of lead
in, for example, blood and water samples, to larger
stationary instruments, such as atomic absorption
spectrometry (AAS) and inductively coupled plasma
mass spectrometry (ICP-MS). This section gives a brief
overview of lead determination in the most common
matrices, blood, water, soil, and sediments, followed
by some examples of more specialized analytical tech-
niques. An overview of analytical methods is given in
Chapter 2.

2 INORGANIC LEAD

2.1 Physical and Chemical Properties
Lead (Pb: CAS 7439-92-1); atomic weight, 207.19

(1 mol).

Only one of the stable, naturally occurring lead
isotopes, 204 Pb, is nonradiogenic, whereas other lead
isotopes are end products of one of three series of radi-
oactive decay: the uranium series (end product: 206 Pb),
thorium series ( 208 Pb), and actinium series ( 207 Pb). As a
consequence, the abundance of its four stable isotopes
( 204 Pb, 206 Pb, 207 Pb, and 208 Pb) varies between different
lead samples. Therefore, lead has the unusual feature
of not having a fi xed natural ratio between its isotopes;
it depends on the geological source of the lead.
Density, 11.3 g/cm 3 ; melting point, 327.5°C; boil-
ing point, 1740°C; oxidation state, lead in inorganic
compounds usually has the oxidation state II, but IV
also occurs.
Solubility: Metallic lead is hard to dissolve in water
but will dissolve in nitric acid and concentrated sulfu-
ric acid. Most lead (II) salts are hard to dissolve (e.g.,
lead sulfi de and lead oxides), but exceptions are found
in, for example, lead nitrate, lead chlorate and—to
some extent—lead sulfate and lead chloride. In addi-
tion, some salts with organic acids are insoluble (e.g.
lead oxalate).
Coordination chemistry: Lead (II) has electronic
properties resulting in a rich coordination chemistry,
giving it the ability to mimic both zinc and calcium
ions in biological systems. On the scale between hard
and soft acids, it is considered an intermediate. It has
the ability to bind to different donor atoms (e.g., O,
N, S, and P). Claudio et al . (2003) made a fascinating
review of the coordination chemistry of lead.
Further information on physical and chemical
properties of lead compounds may be obtained from,
for example, CRC Handbook of Chemistry and Physics
(CRC, 2004).

µ g = 0.004826 µ

2.2.1 Blood Analysis

The most common biological matrix for lead deter-
mination is whole blood. Generally, venous blood,
sampled from the cubital vein of the arm, is analyzed.
The alternative of using capillary samples leads to
some falsely high results because of contamination
even when the personnel collecting the samples are
well instructed (Parsons et al ., 1997). Capillary sam-
pling may, however, be useful for screening purposes,
but its use may be hard to justify in epidemiological
studies.
There are three commonly used principles for deter-
mination of the concentration of lead in blood. These
are ASV, electro thermal AAS (ETAAS; sometimes also
referred to as graphite furnace AAS, GFAAS), and ICP-
MS. All of these can perform very well in determina-
tion of B-Pbs (Bannon and Chisholm Jr., 2001; Parsons
et al ., 2001), but signifi cant differences have been noted
between ASV and ETAAS in samples collected at high
altitudes, possibly because of affected blood chemis-
try (Taylor et al ., 2004). All these techniques often reach
detection limits on the order of 1 g/L and variations

below 5% relative standard deviation in routine deter-
mination of lead concentration in blood. Potentials for
lower detection limits exist but are of little importance
for blood analyses.
The method of ASV is fairly simple, both as regards
sample treatment and instrumentation, whereas
ETAAS and ICP-MS are more expensive and complex
instruments, but also with greater potential. While
ASV and ETAAS have been on the market for many
years, new modifi cations of the ICP-MS technique are
still developing. Cubadda (2004) made a review of its
limitations and modifi cations.
Another method that is not as sensitive, but may
be useful for screening purposes or determination
of blood-lead concentrations at elevated levels, are a
portable testing system developed for screening pur-
poses (Pineau et al ., 2002) and fl ame AAS (FAAS). The
FAAS used to be the “workhorse” of trace element

µ

2.2 Methods and Problems of Analysis
A variety of methods are available for determina-
tion of lead levels in air, soil, water, foods, biological
samples, cosmetics, paint, and other matrices. Instru-
mentation ranges from hand-held X-ray fl uores-
cence (XRF) instruments for direct determination of