Comparative Study of Blood Lead Levels in Uruguayan.pdf

Biol Trace Elem Res (2008) 122:19

–

DOI 10.1007/s12011-007-8056-9

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 ].

: L. Pereira : C. Alvarez : T. Heller : B. De Mattos : C. Piastra : P. Viapiana :

A. Cousillas ( * )

: N. Mañay

Department of Toxicology and Environmental Hygiene, Faculty of Chemistry, University of the

Republic, Montevideo, Uruguay

e-mail: bellcou@adinet.com.uy

O. Rampoldi

Cousillas et al.

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

g/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.

Comparative Study of Blood Lead Levels in Uruguayan Children

Table 1 Data from children

studied in 2004

Children 2004

Number

Age (years)

Total

180

6.39 (0 – 15)

Boys

6.42 (0

–

15)

Girls

6.36 (1 – 15)

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

g/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

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 μ g/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

g/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 0.25 μ g/dl.

We see in the Tables 2 and 3 the results in 2004, and these compared with different

parameters.

Cousillas et al.

Table 2 Results 2004

Population 2004 ( n =180)

BLL ( μ g/dl)

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

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,

< 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

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 (

–

= 0.045).

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

g/dl, with an average BLL

of 9.6

g/dl, coinciding with data from a small study of 1992 [ 15 ].

In the recent 2004 study, children showed significantly lower BLL (5.7 μ g/dl) than those

sampled in 1994 (9.6

< 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.

g/l,

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

(

5.8

(3.0

5.4

(3.0

5.6

(3.0

5.8

(3.0

5.8

(3.0

5.0

(3.0

g/dl)

–

13.0)

–

16.0)

–

13.0)

–

16.0)

–

14.0)

–

16.0)

Comparative Study of Blood Lead Levels in Uruguayan Children

Table 4 Data from children

studied in 1994

Children

Number

Age (years)

BLL ( μ g/dl)

Total

5.2 (2.0 – 11.0)

9.6 (3.4 – 18.6)

Boys

6.2 (2.0

–

11.0)

9.3 (5.4

–

18.6)

Girls

4.8 (3.8 – 10.9)

10.0 (3.4 – 17.9)

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

–

= 47, SD = 3.5, range =

5.3 – 18.6). Thirty-six percent showed values of BLL above 10 μ g/dl.

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

g/dl (

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

the children between 1 and 5years showed values above 10

g/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

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

10 μ g/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

( μ g/dl)

% BLL>10

g/dl

1994

5.2

9.6

2004

180

6.3

5.7

6.7

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