Artículo en PDF
How to cite
Complete issue
More information about this article
Journal's homepage in redalyc.org
Sistema de Información Científica
Red de Revistas Científicas de América Latina y el Caribe, España y Portugal
CADMIUM AND LEAD LEVELS IN DECIDUOUS TEETH OF CHILDREN
LIVING IN MÉXICO CITY
Armando BÁEZ
1
, Raúl BELMONT
1
, Rocío GARCÍA
1
and Juan Carlos HERNÁNDEZ
2
1
Laboratorio de Química Atmosférica, Centro de Ciencias de la Atmósfera, Universidad Nacional Autónoma de México,
Circuito Exterior, Ciudad Universitaria, Coyoacán D. F. 04510, México.
Corresponding author, e-mail:
barmando@atmosfera.unam.mx
2
División de Estudios de Posgrado e Investigación, Facultad de Odontología, Universidad Nacional Autónoma de
México, Circuito Exterior, Ciudad Universitaria, Coyoacán D. F. 04510, México
(Recibido abril 2003, aceptado marzo 2004)
Key words: teeth, children, cadmium and lead exposure, teeth cadmium and lead concentrations, México
ABSTRACT
Cadmium and lead levels in 79 deciduous teeth from children between 5 and 13 years old
living
in the México City Metropolitan Zone were determined by graphite furnace atomic absorption
spectrometry. Lead and cadmium concentrations showed a positively skewed distribution and
results were transformed into logarithms. The geometric mean concentrations (GM) in all teeth
were 0.22
±
3.4 and 10.2
±
2.2 μg g
-1
for cadmium and lead, respectively. No statistical differ-
ences were observed for cadmium and lead concentrations among tooth type, tooth position,
gender, socioeconomic level, and use or no use of color crayons. Cadmium values decreased
with children’s age and lead levels did not show a clear tendency. Statistical
differences were
only observed for cadmium according to age.
Palabras clave: dientes, niños, exposición a cadmio y plomo, concentración de cadmio y plomo en dientes, México
RESUMEN
Se determinaron por espectrometría de absorción atómica con horno de grafito los niveles de
cadmio y plomo en 79 dientes deciduos de niños de 5 a 13 años de edad que residen en la Zona
Metropolitana de la Ciudad de México. Las concentraciones de cadmio y plomo mostraron una
distribución sesgada positivamente por lo que se transformaron a logaritmos base 10. Las
medias geométricas (GM) de las concentraciones de todos los dientes fueron de 0.22
±
3.4 y
10.2
±
2.2 μg g
-1
para cadmio y plomo, respectivamente. No se observaron diferencias
estadísticamente significativas de las concentraciones de cadmio y plomo entre los tipos de
dientes, posición de los dientes, tipo de diente y su posición, sexo, nivel socioeconómico, y el
uso o no uso de crayones de color. Los valores de cadmio decrecieron con la edad y los de
plomo no mostraron una tendencia clara. Sólo se observaron diferencias estadísticamente
significativas entre las concentraciones de cadmio y la edad.
Rev. Int. Contam. Ambient. 20 (3)
XX-XX
, 2004
F
AL
T
A
CORNISA
DE PÁGINAS IMP
ARES
A. Báez
et al.
INTRODUCTION
Deciduous teeth have been used as indicators of long-
term heavy metal exposure. The concentrations of cad-
mium and lead in primary teeth have been shown in sev-
eral previous studies (Triphati
et al
. 1989, Tvinnereim
et
al
. 1997, Bloch
et al
. 1998, Eide
et al
. 1998, Bu-Olayan
and Thomas 1999, Tvinnereim
et al
. 2000).
Cadmium and lead are air and food contaminants and
enter the body by inhalation and ingestion (Nordberg 1978).
Cadmium is a toxic metal with a biological half-life of 10-20
years, and is mainly accumulated in the liver and kidneys
(more than 50% of the body burden) (Nordberg 1978, Hahn
et al
. 1987). At high levels, it may develop degenerative
and inflammatory changes in liver and kidneys (Norén
et
al
. 1987).
(Attrition?)
of plated components, tires wear
and exhaust emissions from motor vehicles are sources of
cadmium in the urban atmosphere (Harrison and Williams
1982). It has been suggested that fragmentation of automo-
bile tires is a likely source of cadmium (Lagerwerff and
Specht 1970, Burton and John 1977). Cadmium seems to
be a naturally occurring element in teeth (Ranhkamo and
Tuompo 1985). Its concentration in teeth depends on the
amount acquired during tooth development (Shearer
et al.
1980, Shearer
et al.
1982). Primary teeth may be used as
indicators of cadmium exposure (Eide
et al
. 1998).
Lead has greatly attracted researchers’ attention due
to its toxicity to humans. Lead intoxication in humans
has neurotoxic effects such as encephalitis, behavioral
disorders and inattention, reduced nerve conduction and
IQ deficit (Fergusson 1990, USDHHS 1993). Exposures
to this metal can be evaluated by measuring lead content
in blood, teeth, hair and bone, which are used to estimate
the lead body burden (Fergusson 1990). Lead is accu-
mulated in bones and teeth (Elinder
et al
. 1988) but the
amount of lead released from teeth is negligible (Steenhout
1982). Its annual aggregation in teeth can be considered
as directly correlated to blood levels. Thus, teeth are good
indicators of environmental lead pollution and have been
used as such by some researchers (Altshuller
et al
. 1962,
Lappalainen and Knnuttila 1981, Steenhout 1982,
Bercovitz
et al
. 1993).
Industry and motor vehicles emissions have been es-
tablished as the most important environmental lead sources,
although glass, pigments, paints, pottery, non-ferrous metal
smelters, accumulator gratings, and the battery manufac-
turing industry are other important lead emission sources.
Vehicles in the México City Metropolitan Zone (MCMZ)
used for many years leaded-gasoline. Lead control strate-
gies have been undertaken to control lead levels in the
MCMZ atmosphere. Reduction of lead in paints, varnishes
and its elimination from food cans and toys (RAMA 1998),
the introduction of unleaded gasoline (Magna-Sin) in 1990
and Premium in 1998, and the mandatory installation of
catalytic converters in new automobiles since 1991, are
some of these strategies. However, despite them, signifi-
cant lead levels might still be found in teeth and blood of
children living in different MCMZ areas.
This study was carried out to investigate cadmium
and lead concentrations in deciduous teeth, to compare
these concentrations among different deciduous teeth
types and to determine whether gender, and years of
residence in the same zone since birth, influenced cad-
mium and lead concentrations in teeth.
MATERIALS AND METHODS
Teeth collection
Deciduous teeth were extracted from or shed by chil-
dren who have been living in the MCMZ since birth and
attending the
Dentistry Faculty peripheral clinics of the
National Autonomous University of Mexico in 1997. 100
deciduous teeth, out of 500 obtained indistinctively from
boys or girls between 5 and 13 years old, were randomly
selected. Twenty-one teeth with fillings, caries or growth
defects were discarded. Each child contributed with one
tooth.
Information on paint type applied to their homes
walls, parent’s scholarship and job (used to determine so-
cioeconomic level), age, gender,
the use or no use of color
crayons,
home address, and clinical history, was gathered
.
Each extracted or shed tooth was placed in a high-
density polypropylene vial containing a 10% sodium hy-
pochlorite solution. Samples were immediately sent to
the Atmospheric Chemistry Laboratory of the Atmo-
spheric Sciences Center for their chemical analysis.
Sample preparation
All glass and plasticware were soaked in a 20%
nitric acid solution for 24 hours and then rinsed thor-
oughly with deionized water. Upon arrival to the labo-
ratory, teeth were rinsed with distilled water. Fergusson
and Purchase (1987), mentioned that it is essential to
clean the teeth prior to analysis and that the removal of
organic material and surface contamination is the ma-
jor cleaning stage. Stack and Delves (1981) used hy-
pochlorite solution to remove organic material. In this
study, the following procedure was used: each tooth
was soaked in 25 ml of a 10% v/v sodium hypochlorite
solution for 24 hours, rinsed with deionized water and
dried at 103
°
C (
for how long?
).
Each tooth was weighed and placed into a 100-mL-
beaker and digested with 1-mL of concentrated double-
distilled nitric acid and 100 μL of hydrogen peroxide. After
complete digestion, the solution was cooled and poured
into a 10 ml volumetric flask, and made up to volume
with deionized water.
Analysis
Cadmium and lead were analyzed by graphite furnace
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
atomic absorption spectrometry at 228 nm and 283.3 nm,
respectively, with a GBC double beam 932AA instrument,
equipped with the unique ultra-pulse deuterium arc back-
ground correction system and coupled with a System 3000
graphite furnace accessory. Pyrolytically coated furnace
tubes and boosted discharge hollow cathode lamps
(Photron Super lamp) were used. The detection and quan-
tification limits of the methods were 1.1 and 3.8 μg L
-1
for
lead, and 0.07 and 0.23 μg L
-1
for cadmium.
Quality control
For internal quality control, two teeth were pow-
ered in a mortar and divided in two portions that were
weighed and placed into a 100-mL-beaker. One of the
portions was spiked with known quantities of cadmium
and lead, and both portions were digested and analyzed
applying the same procedure used for tooth samples.
Recoveries in spiked teeth were 106% for cadmium
and 107% for lead.
All glassware and plasticware were analyzed to guar-
antee their cleanness and the no contamination of the sam-
pling material. Blanks of deionized water with reagents
were included throughout the entire sample preparation
and analytical process. The results indicated that cadmium
and lead concentrations were below the detection limits.
The total error of the analytical method was deter-
mined by quality control check samples prepared in the
laboratory. Ten replicate measurements of each metal
were made. The results showed that the total error was
2.3% and 1.1% for Cd and Pb, respectively.
Statistical analysis
The Statistical Package for the Social Sciences (SPSS)
10.0 was used. Samples were classified according to tooth
type, tooth position, gender, age, socioeconomic level, and
use or no use of color crayons.
Out of 79 healthy teeth (teeth without fillings, caries or
growth defects) used for this study, 38 were from girls
and 41 were from boys. Children were divided into seven
age groups: 5, 6, 7, 8, 9, 10, and
11 years old.
To determine the socioeconomic level, paint type ap-
plied in home walls, parent’s scholarship and job were codi-
fied as follows:
Paint type: enamel, 4; vinyl, 3; others 2, without paint, 1.
Parent’s scholarship: professional, 4; college, 3; high
school, 2; elementary, 1.
Father’s job: professional, 4; employee, 3; trader, 2;
other; 1.
Mother’s job: professional, 4; employee, 3; trader, 2;
home, 1.
The socioeconomic level was calculated by summing
up the numerical values obtained in each classification and
divided into two categories,
10 and >10.
The use of color crayons was codified as 1 for yes and
2 for no.
A Pearson’s correlation was done to define the rela-
tions among teeth cadmium and lead concentrations and
weight of tooth, age, gender, use of color crayons, and
socioeconomic level.
The association between teeth cadmium and lead con-
centrations and the studied variables was calculated using
a one-way analysis of variance (ANOVA).
RESULTS
Histograms of cadmium and lead concentrations in
teeth, show a positively skewed distribution frequency
(
Fig. 1
). Data were transformed to logarithms and a
1.7 - 1.8
.9 - 1.1
.2 - .3
16
12
8
4
0
(a)
.1 - .2
10
8
6
4
2
0
(b)
Fig. 1.
Frequency histograms normalized by logarithmic transfor-
mation: (a) lead concentrations, (b) cadmium concentrations
.2 - .3
.6 - .7
.9 - 1.1
1.3 - 1.4
1.7 - 1.8
16
12
8
4
0
Frecuency
(a)
(b)
Log 10 Pb (
µ
g/g of tooth)
12
10
8
6
4
2
Frecuency
Log 10 Pb (
µ
g/g of tooth)
-.7 - -.6
-.3 - -.2
-1.8 - -1.7
-1.4 - -1.3
-1.1 - -.9
-.1 - -.2
0
A. Báez
et al.
Lilliefors test (Sprent 1989) was done. This test showed
that the largest differences [
F
(
z
i
)
–S
(
z
i-1
)] were 0.075
and 0.069 for lead and cadmium data, respectively. There-
fore, the null hypothesis establishing that the data corre-
sponded to a log-normal distribution, was not rejected at
the 1% significance level. Consequently, geometric means
(GM) and geometric standard deviations (GSD) were
used. The data were transformed into logarithms and
used for all statistical calculations.
Concentrations were expressed as μg of metal/g of
tooth (dry weight). Tooth weight ranged from 0.0408
to 0.7728 g.
Cadmium and lead concentrations ranged from 0.02
to 2 and from 1.7 to 58 μg/g with GM of 0.22
±
3.4 μg/
g and 10.2
±
2.2 μg/g, respectively.
No statistical differences were observed for cad-
mium and lead concentration when comparing teeth
type, position and type vs. position. (
Tables I
and
II
).
The comparison of cadmium and lead concentrations
between first and second molars was not made be-
cause only 2 second molars were sampled (
Table II
).
No statistical differences were observed for cadmium
and lead concentrations according to gender (
Fig. 2
).
Regarding age (
Table III
), there was a statistical
difference between cadmium concentrations GM only;
the 5 years old group showed a higher GM concentra-
tion than the other groups.
There were no statistical differences between chil-
dren who used color crayons and those who did not
(
Table IV
).
No statistical differences were observed for cad-
mium and lead concentrations according to socioeco-
nomic level.
The Pearson’s correlation coefficient shows that teeth
Tooth
N*
Lead
Cadmium
GM ± GSD
Range
GM ± GSD
Range
Type:
F = 0.202
F = 2.426
p = 0.818
p = 0.095
Incisors
56
10.5 ± 2.1
1.7 – 58
0.27 ± 3.1
0.02 – 1.9
Canines
12
9.2± 3.0
1.8 - 48
0.14 ± 5.1
0.02 – 1.6
Molars
11
9.4± 1.9
3.8 – 22
0.14 ± 2.7
0.02 – 0.6
Position:
F = 0.007
F = 0.445
p = 0.935
p =0.507
Upper
53
10.1 ± 2.3
1.7 - 58
0.21 ± 3.5
0.02 – 1.8
Lower
26
10.3 ± 2.0
2.0 -29
0.26 ± 3.2
0.05 – 1.9
TABLE I.
LEAD AND CADMIUM GEOMETRIC MEANS
(GM) AND GEOMETRIC STANDARD DEVIATIONS
(GSD), IN μg OF METAL/g OF TOOTH, WITH RE-
GARD TO TOOTH TYPE AND TOOTH POSITION
* Number of samples
Tooth
N*
Lead
Cadmium
GM ± GSD
Range
GM ± GSD
Range
Incisors:
F = 0.056
F = 0.007
p = 0.814
p = 0.935
Upper
34
10.2 ± 2.2
1.7 – 58
0.27 ± 3.1
0.02 – 1.8
Lower
22
9.7 ± 2.1
2.0 – 29
0.26 ± 3.4
0.02 – 1.9
F = 0.387
F = 0.387
p = 0.537
p = 0.537
Central
27
9.8 ± 1.1
2.4 – 27
0.30 ± 3.1
0.02 – 1.5
Lateral
29
11.3 ± 1.2
1.7 - 58
0.25 ± 3.2
0.05 – 1.9
Canines:
F = 0.038
F = 0.938
p = 0.850
p = 0.356
Upper
11
9.0± 1.4
1.8 - 48
0.12 ± 5.1
0.02 – 1.6
Lower
1
11.4
———
0.65
———
Molars:
F = 2.488
F = 0.202
p = 0.149
p = 0.663
Upper
8
8.0± 1.2
3.8 – 20
0.13 ± 3.2
0.02 – 0.6
Lower
3
14.8± 1.4
7.9 – 22
0.17 ± 1.3
0.13 – 0.2
F = 1.304
F = 0.081
p = 0.283
p = 0.783
Firsts
9
10.4± 1.2
3.8 – 22
0.14 ± 2.8
0.02 – 0.6
Seconds
2
6.0
4.6 – 7
0.11
0.06 – 0.2
TABLE II.
LEAD AND CADMIUM GEOMETRIC MEANS
(GM) AND GEOMETRIC STANDARD DEVIA-
TIONS (GSD), in μg of metal/g of tooth, WITH RE-
GARD TO TOOTH TYPE AND ITS POSITION
* Number of samples
0.02
0.02
1.6
1.9
2.9
3.9
0.26
0.2
(a)
F = 0.778, p = 0.381
n = 38
n = 41
11.3
9.2
1.6
57.5
49
1.8
2.1
2.2
(b)
F = 1.317, p = 0.255
n = 38
n = 41
Gender
Gender
Female
Male
Female
Male
µ
g g
-1
µ
g g
-1
5
4
3
2
1
0
-1
60
40
20
0
n = 38
n = 41
n = 41
n = 38
Fig. 2.
Plots of cadmium and lead concentrations according to gender: (a) cadmium concentrations, (b) lead concentrations. Circles, triangles and
dashes indicate geometric means; standard deviations, and minimum and maximum concentrations, respectively. Values in boxes indicate
the results of the ANOVA test
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
cadmium and lead concentrations correlated (r = 0.552,
p < 0.001) and only teeth cadmium concentrations cor-
related with the weight of tooth (r = -0.395, p < 0.001),
type of tooth (r = -0.230, p = 0.042), and age (r = -0.370,
p = 0.001).
DISCUSSION
In this study, no statistical differences for cadmium
and lead concentrations in molars, incisors and canines
were found. The sample size was probably an important
factor in the results found. These teeth mineralize at dif-
ferent, but overlapping, times (Schour and Massler 1941).
So, they could have retained variable amounts of lead. No
statistical differences were observed between lower and
upper teeth, nor between the positions of the incisors. The
relationship of lead levels and tooth positions seems to
vary among different studies (Altshuller
et al
. 1962,
Mackie
et al
. 1977, Pinchin
et al
. 1978, Delves
et
al
. 1982,
Grandjean 1986, Rabinowitz
et al
. 1989, Alexander
et al.
1993). Tvinnereim
et al
. (2000) did not find cadmium con-
centration variations, in agreement with our results.
Our results did not show a clear relation between
teeth lead concentration and age, this agrees with Mackie
et al
. (1977). In contrast, teeth cadmium concentrations
decreased as age increased, agreeing with Bayo
et al
.
(2001). The negative correlation between teeth cadmium
concentrations and age, confirms this association. No
plausible explanation was found on why the 5 years old
group had higher cadmium concentrations.
The small
sample size could have been an important factor influ-
encing the relation between decreasing teeth cadmium
and age increase.
Tooth cadmium and lead levels did not seem to de-
pend on gender as established by Mackie
et al
. (1977),
Ewers
et al
. (1982), Gil
et al.
(1994), Bu-Olayan and
Thomas (1999), and Bayo
et al
. (2001) in accordance
with our results.
Regarding socioeconomic level, although no statisti-
cal differences were found, our cadmium concentrations
results agree with the results of Bayo
et al
. (2001), who
found that families with a law socioeconomic status
showed no statistically significant higher values.
Bayo
et al
. (2001), have reported significant correla-
tions between teeth cadmium and lead concentrations,
and between cadmium levels and tooth weight, tooth type,
and age. In this study, only significant correlations for
cadmium levels were observed, a fact that cannot be
explained.
Age
N*
Lead
Cadmium
(yr.)
GM ± GSD
Range
GM ± GSD
Range
F = 2.021
F = 2.838
p = 0.074
p = 0.015
5
6
12.5
±
1.6
7.8 – 27.5
0.63
±
2.0
0.26 – 1.6
6
26
9.6
±
2.2
2.0 – 57.5
0.27
±
3.4
0.02 – 1.9
7
19
9.2
±
2.3
1.7 – 31.6
0.22
±
3.2
0.03 – 1.4
8
13
10.7
±
1.9
3.1 – 27.5
0.25
±
2.7
0.04 – 1.1
9
3
35.0
±
1.3
29.5 – 49.0
0.37
±
3.8
0.12 – 1.6
10
5
12.6
±
1.8
5.2 – 23.4
0.08
±
3.4
0.02 – 0.2
11
7
6.3
±
2.8
1.8 – 20.4
0.07
±
3.3
0.02 – 1.6
TABLE III.
LEAD AND CADMIUM GEOMETRIC MEANS
(GM) AND GEOMETRIC STANDARD DEVIA-
TIONS (GSD), IN μg OF METAL/g OF TOOTH,
ACCORDING TO CHILDREN’S AGE
* Number of samples
Variable
N*
Cadmium
Lead
GM ± GSD
Range
GM ± GSD
Range
Use of
color crayons:
F = 0.756
F = 2.722
p = 0.387
p = 0.103
Children who
use them
66
0.21 ± 3.6
0.02 – 1.9
9.5 ± 2.3
1.6 – 57
Children who
do not
13
0.3 ± 2.4
0.08 – 1.6
14.1 ± 1.6
6.3 – 30
Socioeconomic
level:
F = 0.909
F = 0.116
p = 0.343
p = 0.734
Low
52
0.25 ± 3.3
0.02 – 1.9
10.4 ± 2.3
1.7 -57
High
27
0.19 ± 3.5
0.02 – 1.4
9.7 ± 2.0
1.9 - 32
TABLE IV.
LEAD AND CADMIUM GEOMETRIC MEANS (GM) AND
GEOMETRIC STANDARD DEVIATIONS (GSD), IN μg OF
METAL/g OF TOOTH, ACCORDING TO YEARS OF RESI-
DENCE, USE OF COLOR CRAYONS, AND SOCIOECONOMIC
LEVEL
* Number of samples
A. Báez
et al.
CONCLUSIONS
No statistical differences were found for cadmium
and lead concentrations between the different tooth types
and positions, and between teeth cadmium and lead lev-
els and the studied variables. This was possibly due to
the small sample size. Therefore,
the sample size should
be increased in further investigations
.
Also, the inclusion
of other variables such as feeding and smoking habits
could aid to understand the variation of heavy metals
concentration in teeth.
ACKNOWLEDGMENTS
This study was partially supported by the Dirección
General de Asuntos del Personal Académico (PAPIIT),
Universidad Nacional Autónoma de México, Project No.
IN209996. The authors are indebted to Hugo Padilla G.
for the review of the English manuscript and to Delibes
Flores Román for his support in computation.
REFERENCES
Alexander L.M, Heaven A., Delves H.T., Moreton J. and
Trenouth M.J. (1993). Relative exposure of children to lead
from dust and drinking water. Arch. Environ. Health 48,
392-400.
Altshuller L.F., Halak D.B., Landing B.H. and Kehoe R.A.
(1962). Deciduous teeth as an index of body burden of
lead. J. Pediat. 60, 224-229.
Bayo J., Moreno Grau S., Martínez M.J., Moreno J., Angosto
J.M., Guillén Pérez J.J., García Marcos L. and Moreno-
Clavel J. (2001). Environmental and physiological factors
affecting lead and cadmium levels in deciduous teeth.
Arch. Environ. Contam. Toxicol. 41, 247-254.
Bercovitz K., Helman J., Peled M. and Laufer D. (1993). Low
lead level in teeth in Israel. Sci. Total Environ. 136, 135-
141.
Bloch P., Shapiro I.M, Soule L., Close A. and Revich B. (1998).
Assessment of lead exposure of children from K-XRF mea-
surements of shed teeth. Appl. Radiat. Isot. 49, 703-705.
Bu-Olayan A.H. and Thomas B.V. (1999) Dental lead levels in
residents from industrial and suburban areas of Kuwait.
Sci. Total Environ. 226, 133-137.
Burton K.W. and John E. (1977). Study of heavy metal con-
centrations in the Rhodda Fawa, South Wales. Wat. Air
Soil Pollut. 7, 45-68.
Delves H.T., Clayton B.E., Carmichael A., Bibearm M. and Smith
M. (1982). An appraisal of the analytical significance of
tooth-lead measurements as possible indices of environ-
mental exposure of children to lead. Ann. Clin. Biochem.
19, 329-337.
Eide R., Tvinnereim H.M., Fosse G., Kjosnes M. and Nyhaug
A. (1998). Lead and cadmium in primary teeth from Illinois,
USA. Int. J. Environ. Stud. 55, 25-39.
Elinder C.G., Gerhardsson L. and Oberdoerster G. (1988). Bio-
logical monitoring of toxic metals-Overview. In:
Biologi-
cal monitoring of toxic metals
(T.W. Clarkson, L. Friberg,
G.J. Nordberg, P.R. Sager, Eds.). Plenum Press, New York,
pp. 18.
Ewers U., Brockhaus A., Winneke G., Freier I., Jermann E. and
Krämer U. (1982). Lead in deciduous teeth of children liv-
ing in a non-ferrous smelter area and a rural area of the
FRG. Int. Arch. Occup. Environ. Health
50
, 132-151.
Fergusson J.E. (1990).
The heavy elements: Chemistry, envi-
ronmental impact and health effects
. Pergamon Press, Ox-
ford, New York, Seoul, Tokyo, pp. 569-570.
Fergusson J.E. and Purchase N.G. (1987). The analysis and
levels of lead in human teeth: A review. Environ. Pollut. 46,
11-44.
Gil F., Pérez M.L., Facio A., Villanueva E., Tojo R. and Gil A.
(1994). Dental lead in the Galician population, Spain. Sci.
Total Environ. 156, 145-150.
Grandjean P., Lyngbye T. and Hansen O.N. (1986). Lead con-
centration in deciduous teeth: variation related to tooth
type and analytical technique. J. Toxicol. Environ. Health
19, 437-445.
Hahn R., Ewers U., Jermann E., Freier I., Brockhaus A. and
Schlipköter H.W. (1987). Cadmium in Kidney cortex of in-
habitants of North-West Germany: its relationship to age,
sex, smoking and environmental pollution by cadmium. Int.
Arch. Occup. Environ. Health 59, 165-176.
Harrison R.M. and Williams C.R. (1982). Airborne cadmium,
lead and zinc at rural and urban sites in North-West En-
gland. Atmos. Environ. 16, 2669-2681.
Lagerwerff J.V. and Specht A.W. (1970). Contamination of road-
side soil and vegetation with cadmium, nickel, lead zinc.
Environ. Sci. Technol. 4, 583-586.
Lappalainen R. and Knuuttila M. (1981). The concentrations
of Pb, Cu, Co, and Ni in extracted permanent teeth related
to donor’s age and elements in the soil. Acta Odontol.
Scand. 39, 163-167.
Mackie A.C., Stephens R., Townshend A. and Waldron H.A.
(1977). Tooth lead levels in Birmingham children. Arch.
Environ. Health 32, 178-185.
Nordberg M. (1978). Studies on metallothionein and cadmium.
Environ. Res. 15, 381-404.
Norén J.G., Hulthe P. and Gillberg C. (1987). Analysis of lead
and cadmium in deciduous teeth by means of poten-
ciometric stripping analysis. Swed. Dent. J. 11, 45-52.
Pinchin M., Newhan J. and Thompson R. (1978). Lead, cooper
and cadmium in the teeth of normal and mentally retarded
children. Clin. Chim. Acta 85, 89-94.
Rabinowitz M., Bellinger D. and Levinton A. (1989). The blood
lead-tooth relationship among Boston children. Bull.
Environ. Contam. Toxicol. 43, 485-492.
RAMA. (Red Automática de Monitoreo Atmosférico). (1998).
Informe anual de la calidad del aire en el valle de México
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
1997. Gobierno del Distrito Federal, Secretaría del Medio
Ambiente, Dirección General de Prevención y Control de la
Contaminación, Comisión Ambiental Metropolitana. p. 34.
Ranhkamo A. and Tuompo H. (1985). Uptake of cadmium in
developing rat teeth in organ culture. Scand. J. Dent. Res.
93, 198-203.
Schour I. and Massler M. (1941). The development of human
dentition. J. Am. Dent. Assoc. 28, 1153-1160.
Shearer T.R, Johnson J.R. and DeSart D.J. (1980). Cadmium
gradient in human and bovine enamel. J. Dent. Res. 59,
1072.
Shearer T.R., Johnson B.E., Ridlington J.W. and Whanger P.D.
(1982). Chemical location of cadmium in developing rat
molars. J. Dent. Res. 61, 510-511.
Sprent P. (1989).
Applied non-parametric statistical meth-
ods
. Chapman and Hall, London, New York, pp. 87.
Stack M. and Delves H.T. (1981). Tooth lead analysis-An
interlaboratory survey. Int. Symp. Harmonization of Col-
laborative Anal. Studies, Finland, p. 115-118.
Steenhout A. (1982). Kinetics of lead storage in teeth and
bones: An epidemiological approach. Arch. Environ. Health
37, 224-231.
Triphati R.M., Khandekar R.N., Raghunath R. and Mishra U.C.
(1989). Assessment of atmospheric pollution from toxic
heavy metals in two cities in India. Atmos. Environ. 23,
879-883.
Tvinnereim H.M., Eide R., Riise T., Wesenberg G.R., Fosse G.
and Steinnnes E. (1997). Lead in primary teeth from Nor-
way: changes in lead levels from the 1970s to the 1990s.
Sci. Total Environ. 207, 165-177.
Tvinnereim H.M., Eide R. and Riise, T. (2000). Heavy metals in
human primary teeth: some factors influencing the metal
concentrations. Sci. Total Environ. 255, 21-27.
USDHHS (US Department of Health and Human Services).
(1993). Toxicological profile for lead (UPDATE). Prepared
by Clement International Corporation Under contract No.
205-88-0608 for U.S. Department of Health and Human
Services, Public Health Service, Agency for Toxic Sub-
stances and Disease Registry. ATSDR/TP-92/12. Atlanta,
GA, pp. 6.
logo_pie_uaemex.mx