Comparative Study of Blood Lead Levels in Uruguayan
Children (1994

–2004)

A. Cousillas

&

L. Pereira

&

C. Alvarez

&

T. Heller

&

B. De Mattos

&

C. Piastra

&

P. Viapiana

&

O. Rampoldi

&

N. Mañay

Received: 29 August 2007 / Revised: 31 August 2007 / Accepted: 23 September 2007 /
Published online: 30 October 2007

# Humana Press Inc. 2007

Abstract Lead does not fulfill any physiological function in the human body. It is
generally accepted that the blood lead level (BLL) is the best exposure index, as there is an
excellent correlation between the actual exposure of the individual and the concentration of
lead in blood. In Uruguay, lead contamination becomes a matter of public concern in 2001,
giving rise to a sensitization in the population, which in many cases brought about a change
in hygienic and dietary habits of the children. In 2004, after the leaded gasoline phasing out
process in Uruguay was completed, we studied non-exposed children to correlate BLL with
variables such as age, sex, area of residence, and available environmental lead data and
compared these results with those from our similar screening studies 10years ago. The main
result of this comparison is that BLL from children in our country had a significant decrease
between 1994 and 2004.

Keywords Lead . Blood lead level . Children . Comparison . Environmental exposure .
Decrease

Introduction

Everyday, children breathe, eat, and drink chemical substances that are in the air, in food,
and in water. They are the main victims of these substances because, taking into account
their weight and height, they breathe, eat, and drink more than adults. Besides, children
play and live closer to the ground or carpets, where toxic substances often accumulate. In
addition, they have the habit of taking their fingers and other objects to the mouth. This
facilitates the entrance of dangerous substances to their bodies, affecting their brain and
some functions of learning and behavior [

1

,

2

].

Biol Trace Elem Res (2008) 122:19

–25

DOI 10.1007/s12011-007-8056-9

A. Cousillas (

*)

:

L. Pereira

:

C. Alvarez

:

T. Heller

:

B. De Mattos

:

C. Piastra

:

P. Viapiana

:

O. Rampoldi

:

N. Mañay

Department of Toxicology and Environmental Hygiene, Faculty of Chemistry, University of the
Republic, Montevideo, Uruguay
e-mail: [e-mail]

Lead is one of such dangerous substances. This metal constitutes an environmental

pollutant of high risk for human health, and its toxic effects are well known, although
symptomatology is not evident below very high levels of lead in blood (blood lead level,
BLL), the children population being especially vulnerable [

2

,

3

].

The biological effects of lead and its symptoms will depend, among others, on the blood

levels reached and the age of the patient [

4

,

5

].

Between the years 2001 and 2003, our Department of Toxicology demonstrated on a

group of presumably exposed children that their values of lead in blood decrease
significantly when appropriate hygienic dietary measures are adopted [

6

].

Lead does not fulfill any physiological function in the human body; therefore, the level

of lead in blood should be zero [

1

,

7

].

It is generally accepted that the level of lead in blood is the best exposure index, as there

is an excellent correlation between the actual exposure of the individual and the
concentration of lead in blood [

8

,

9

].

Lead in whole blood is analyzed, as lead circulates 95% bound to the erythrocite [

10

].

In Uruguay, it was not until 2001 that lead exposure became a matter of public concern,

when cases of children with BLL above 20

μg/dl appeared in some areas of a low-income

neighborhood of Montevideo, called La Teja [

11

]. There, the worst situation found was in

soil samples from some slum settlements which showed more than 3,000ppm of lead due to
scrap land fillings [

12

,

13

].

At the Faculty of Chemistry, our Department of Toxicology and Environmental Hygiene

has been assessing heavy-metal exposure in different Uruguayan populations, being lead its
main research line since 1986, with QA/QC analytical results. Therefore, when the lead
issue arose in 2001, the authorities could take advantage of our 15-year scientific
experience in the analytical determination of lead in blood. We had previously studied
groups of workers, children, and general population, producing scientific publications and
several reports [

14

–

19

].

The use of tetraethyl lead in gasoline (replaced in 2004 by terbuthyl-methyl-ether) and

the existence of lead pipes for the drinking-water supply in older buildings are the main
sources of lead exposure for the general population. Living in or near manufacturing areas
as well as the incorrect handling of lead materials and solid wastes are also relevant sources
of non-occupational exposure [

11

,

12

,

14

,

17

].

In 2004, after the leaded gasoline phasing out process in Uruguay was completed, we

studied non-exposed children to correlate BLL with variables such as age, sex, area of
residence, available environmental lead data, among others.

We compared these results with those from our similar screening studies 10 years ago to

assess the current risk factors with a statistical approach [

15

,

18

].

The objective is to present the main changes observed in the BLLs of Uruguayan

children populations within a 10-year period (1994

–2004) considering the different actions

to prevent lead exposure risk.

Materials and Methods

Lead exposure was determined by measuring BLL.

Field studies in 2004 were made in volunteer randomly sampled children (0

–15 years

old) from Montevideo City and a rural area of Uruguay.

The children sampling 2004 campaign was made during an 8-month period and

comprised those children visiting a Social Security Care Center for general health control.

20

Cousillas et al.

These children populations (

n = 180) were parent volunteers and randomly selected. Most

of them were living in Montevideo and surroundings (58.8%). Data were collected from
each individual regarding age, house and school addresses, intensity of traffic near their
houses, and smoking habits of their parents (Table

1

).

Analytical Method Description

After cleaning the skin, 5ml of blood was obtained from the cubital vein in heparin-
moistened evacuated disposable syringes using injectable sodium heparin 25,000UI [

20

] or

Vacutainer® tubes [

21

]. Both had been found to contain no detectable amounts of lead

(corresponding to less than 3

μg/dl blood). Samples were kept in the same labeled syringe or

Vacutainer and frozen at

−20°C until their analysis.

BLLs were determined by flame atomic absorption spectrophotometry (283.3nm, Perkin

Elmer 306).

This method was contrasted with intercalibration programs [

22

,

23

]. It was based on the

NIOSH method (National Institute for Occupational Safety Health), original method
P&CAM 208 [

22

] modified by substituting the ammonium pirrolidyn dithiocarbamate

with

N,N dithiocarbamate diethilammonium (DDDC) resulting a lead complex more stable

over time. This allows processing several samples at the same time, without risk of
decomposition up to the moment of the measurement.

In practice, 2ml of the chelation/extraction agent (0.12ml DDDC, 1g Triton X100 in

100ml of MIBK) was added to 4ml of whole blood and vigorously shaken for 25min (IKA-
IBRAX-VXR, 1,800rpm). Detection limit was 3

μg/dl blood. This method was validated by

the Laboratory of Occupational and Environmental Medicine of the University of Lund
(Sweden), and results were contrasted with techniques such as electrothermal atomization
and inductively coupled plasma

–mass spectroscopy.

Since 1987, the Laboratory of the Department of Toxicology and Environmental

Hygiene of the Chemistry Faculty takes part in an interlaboratory program of lead in blood
analysis with Spain [

24

].

Results

Determination of lead in blood is the most widely used indicator to evaluate the integral
exposure to this metal. Recommended values for BLL are less than 10

μg/dl for children

[

25

].

Lead does not fulfill any physiological function in the human body, so BLL should be

zero. Patterson [

26

] established that the

“normal level” for lead is 0.0025ppm or 0.25μg/dl.

We see in the Tables

2

and

3

the results in 2004, and these compared with different

parameters.

Children 2004

Number

Age (years)

Total

180

6.39 (0

–15)

Boys

99

6.42 (0

–15)

Girls

81

6.36 (1

–15)

Table 1 Data from children
studied in 2004

Comparative Study of Blood Lead Levels in Uruguayan Children

21

A statistical study applying the Mann

–Whitney test (a non-parametric test) was

performed, using a confidence level of 95%, alpha = 0.05.

All the statistical calculations were made considering the BLL with sex, age, the

smoking habits of the persons sharing the home, whether they drank tap water or not, and
residence in Montevideo and outskirts or countryside.

Only one of the comparative studies, corresponding to the boys and girls, showed a

statistically significant difference,

p < 0.05, with the boys exhibiting higher BLL than girls.

The study of comparison between populations of children living in Montevideo and in

the countryside had a result on the limit of being a significant difference or not, presenting
p = 0.0725. This value suggests deepening the research.

In all the other cases, the differences were not statistically significant, with values of

p ranging from 0.5265 to 0.9772.

In 1994, a similar study had been performed on 47 children (ages 2

–11) from different

parts of the country. The population of children randomly corresponded to those attending
the same public health care center, who volunteered for this study. The cases with (other)
several possible sources of exposure were left out. This population is formed by children of
the whole country. The same questionnaire was made to them [

15

,

18

]. Table

4

shows data

from children studied in 1994.

Associations between BLL and single independent variables were assessed using linear

regression. Simultaneous impact of several factors was analyzed using multiple linear
regression. No statistically significant difference was found as regards to relationship
between BLL and sex or smoking parents. However, this study of 1994 [

15

] showed a

positive correlation of BLL with traffic intensity at school (

p = 0.045).

It was found that 36% of the children showed BLL above 10

μg/dl, with an average BLL

of 9.6

μg/dl, coinciding with data from a small study of 1992 [

15

].

In the recent 2004 study, children showed significantly lower BLL (5.7

μg/dl) than those

sampled in 1994 (9.6

μg/l, p < 0.001).

In 1994, 36% of the BLL were above the intervention value, while in 2004, only 6.7%

of the BLL were above this value.

Table 3 Results 2004

N=180
children

Montevideo
and
surroundings

Countryside

Living
with
smokers

Not living
with
smokers

Drinking
tap water

Not drinking
tap water

BLL average

(

μg/dl)

5.8

(3.0

–13.0)

5.4

(3.0

–16.0)

5.6

(3.0

–13.0)

5.8

(3.0

–16.0)

5.8

(3.0

–14.0)

5.0

(3.0

–16.0)

Population 2004 (

n=180)

BLL (

μg/dl)

SD

Total

5.7 (3.0

–16.0)

2.3

Girls

5.4 (3.0

–13.0)

2.0

Boys

5.9 (3.0

–16.0)

2.5

Table 2 Results 2004

22

Cousillas et al.

Discussion

Our obtained results for BLLs in the studied population are described in Table

5

.

Up to the year 1994, little official attention was paid to environmental lead exposure,

although our research group had carried out several studies that were published during the
1990s decade reviewed by Mañay et al. [

14

].

By that time and still now, Montevideo had several lead-emitting industries, most of

them in residential areas. Old buildings and houses still had lead pipelines in their water
supply.

In addition, primary gasoline used in Uruguay up to December 2003 contained lead

tetraethyl as an antiknock agent (150

–300mg/l). It is well known that a clear decrease in

BLL has been associated with the elimination of lead in gasoline in USA and Sweden
[

27

,

28

].

In 1994, the average value of BLL in children was 9.8

μg/dl (n = 47, SD = 3.5, range =

5.3

–18.6). Thirty-six percent showed values of BLL above 10μg/dl.

In USA, 17% of children in preschool age had values of lead in blood above 15

μg/dl,

according to an ATSDR study of 1988 [

29

]. In 1994, the results of Phase I of the Third

National Health and Nutrition Examination Survey NHANES III carried out in USA
between 1988 and 1991 were published, showing great changes in the BLLs of the
population [

27

]. The total average of BLLs of population between 1 and 74years old

decreased 78%, from 12.8 to 2.8

μg/dl. Only 4.5% of the general population and 8.9% of

the children between 1 and 5years showed values above 10

μg/dl. This decrease in the

BLL average was observed in the whole population, considering races, sex, socioeconomic
level, etc.

Phase II of NHANES III, performed between 1991 and 1994, shows that values continue

diminishing. The total geometric average of lead in blood for the whole population older
than 1year is 2.3

μg/dl. Only 4.4% of children between 1 and 5years exhibit values above

10

μg/dl [

9

,

30

].

In the 1990s, European countries like Denmark and Germany had already determined

BLL values for their children population that were lower than those from our country
[

31

,

32

].

Table 5 Results for BLLs vs the compared studied populations

Social Security
Care Center

Children
(total)

Average age
(years)

Average BLL
(

μg/dl)

% BLL>10

μg/dl

1994

47

5.2

9.6

36

2004

180

6.3

5.7

6.7

Children

Number

Age (years)

BLL (

μg/dl)

Total

47

5.2 (2.0

–11.0)

9.6 (3.4

–18.6)

Boys

26

6.2 (2.0

–11.0)

9.3 (5.4

–18.6)

Girls

21

4.8 (3.8

–10.9)

10.0 (3.4

–17.9)

Table 4 Data from children
studied in 1994

Comparative Study of Blood Lead Levels in Uruguayan Children

23

Children 7

–8years old from Aarhus (Denmark) showed a mean value in different

populations between 4.1 and 6.2

μg/dl (1.7–14.5) [

31

]. In a group of children 7

–8years old

from rural and urban zones in the south of Sweden (

N = 154), there was found a mean value

of lead in blood of 3.3

μg/dl (1.5–7.1) in 1988 [

33

]. In these studies, it is clear that there had

been no lead in gasoline for many years.

Conclusions

The values of lead in blood from children in our country have had an important decrease
between 1994 and 2004.

Lead contamination becomes a matter of public concern in 2001, giving rise to a

sensitization in the population, which in many cases brought about a change in hygienic
and dietary habits of children.

From 1995 on, there was an increase in the use of gasoline with lesser lead content,

which was completely eliminated by 2004.

The State Waterwork has implemented in recent years a program of substitution of lead

pipelines.

The observed changes suggest a decrease in the contribution of environmental lead to

the overall exposure of children. This could be the result of several facts, mainly: the
gradual phasing out of leaded gasoline, the progressive substitution of lead pipes for
drinking water supply, and the improvement of education and hygienic habits in children. In
general, it is the consequence of a new attitude of the population, who is now more aware
of the lead health risks.

We conclude that there is a significant change in preventing lead exposure due to the

public sensitization, together with the integration of multidisciplinary actions promoted,
although our country still does not have a complete official surveillance-screening program,
including human population and the environment (air, water, and soil). In relation to lead
workers, new laws have been approved, and now, lead in blood must be controlled in the
health certificate protocol once per year.

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25