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Access 
Original Article
Effectiveness
of hair lead concentration as biological indicator of
environmental and professional exposures.
Nafti Mariem1,3,*,
Bani Mejda1,2, Essid
Dorra2, Magroun Imene
2, Hannachi Chiraz 3, Hamrouni
Béchir3, HabibNouaigui1.
|
1: Tunisian
Occupational Safety and Health Institute Tunis ,
Tunisia. 2: College of Medicine
Tunis, Tunis el Manar
University,
Tunisia. 3: Department of chemistry, Sciences
Faculty of Tunis, The University of Tunis el Manar, Tunisia. *
Corresponding
author Correspondence to: nafti_mariem@yahoo.fr Publication data: Submitted:
January 15, 2020 Accepted:
May 4, 2020 Online:
June 30, 2020 This article was subject to full peer-review. This is an open access article distributed under the terms of the
Creative Commons Attribution Non-Commercial License 4.0 (CCBY-C) allowing to share and adapt. Share: copy and redistribute the material in any medium or
format. Adapt: remix, transform, and build upon the licensed material. the work provided must be properly cited and cannot be used for
commercial purpose. |
Abstract: Introduction: Biological
monitoring is highly recommended to assess occupational and environmental
exposures to toxic chemicals. In this context, blood and urine are
conventional matrices for lead poisoning biotoxicological
assessment. Blood and urine analysis are more contributive for recent lead
exposure. Chronic lead exposure may have different characteristics. long-term exposure could be
responsible of insidious poisoning which cannot always be assessed by these
usual matrices. The aim of this study is to demonstrate that human hair can
be used as an alternative matrix to detect chronic toxic exposure among
occupationally and non-occupationally lead-exposed subjects. Material and Method: This
case-control study analyzed blood, urine and hair sampled from 40 exposed
workers versus a control group of 30. Particulate matters of lead are collected
from different workplace ambient air. Analysis is realized using the graphite
furnace atomic absorption spectrometry. Correlations are studied between the
different matrices in both groups and between seniority and lead
concentrations in biological samples. Results: This
study concerned 70 male subjects: forty battery manufacturing factory workers
and thirty controls (non-exposed to lead in their workplaces). The results
showed a significant correlation between lead levels in the three matrices and
the intensity of exposure among both groups (Pb
hair-blood P=0.017;Pb hair-urine<0.000). Hair lead
concentrations study among cases in function of occupational seniority
confirmed the stability of this matrix (Pb>3000
µg/g of hair
at 20 years). The study of hair lead concentration according to workplace
showed a significantly higher exposure for the station of assemblers. Conclusion: Hair
is an efficient biological sample to assess lead poisoning especially for chronic
exposure. Hair is easy to collect, to handle and gives reproducible results
that may be useful in monitoring of exposed workers. Key words: Lead
poisoning, monitoring, exposure, hair samples. |
Introduction
Lead (Pb) has many useful properties in various industrial
sectors such as battery and ammunition manufacturing. This ubiquitous heavy
metal is toxic and considered as a cumulative poison that causes several health
problems. According to an investigation carried out in Tunisia by the Tunisian
Occupational Risk Cartography, 6714 workers are exposed to lead. This
represented around 1 % of the total number of workers in 2016 [1-3]. Lead can
cause many health problems such as digestive disorders, tubular nephropathies,
and hemolytic anemia. For Pb-Blood levels
>600µg/L, peripheral neuropathy, encephalopathy, psychological syndromes can
be observed. For the assessment of occupational safety, an effective biomarker
that could reflect chronic lead exposure is required. Human hair is one of the major vehicles of
the substances excretion. Several studies revealed that hair levels are
significantly higher than those of blood or urine regarding exposure to heavy
metals. Hair is widely used in forensic medicine. Recently, it became more
exploited in clinical and biological monitoring tests [4,5].
The advantages
include sample stability, easy storage, and significant levels in long-term
chemicals exposure.
This study tried
first to verify the correlation between lead levels in hair, blood, and urine.
The second aim was
to assess lead exposure levels in different workplaces in order to implement biomonitoring preferences according to each matrix lead
concentration.
Materials and Methods
The
study was conducted in a battery manufacturing factory.
Samples were taken from male volunteers belonging to the same age group.
Written informed consent was obtained from all participants before sampling.
The
study was approved by our ethics committee according to the Helsinki
declaration principles. Forty exposed workers and thirty controls were
included. Sensitive methods are employed for the occupational and environmental
lead exposure assessment.
Electro-thermal
atomization atomic absorption spectrometry (ETAAS) was used to detect lead in
air, blood and urine. Methods analytical performances were checked according to
ISO17025 exigencies to ensure the reliability of the results. Linearity
(R2 >0.998 for blood and urine and > 0.999 for hair samples
and air), fidelity and recovery were studied.
The
limits of detection are close to 1µg/L. The washing protocol of hair samples
with acetonitrile and water ensured the elimination of more than 98.6% of
external contamination. Storage of samples was codified to avoid
inter-contamination.
Environmental measurements
The
atmospheric measurements are performed by taking ambient air samples from
different workstations. Cellulose ester filters are used (porosity 0.8 µm and
37 mm diameter). After acid mineralization, Lead is quantified using graphite
furnace atomic absorption spectrometry.
Reagents and chemicals
Chemicals
and reagents used in this study are of analytical grades.
Standard solutions of lead are prepared daily by dilution of 1000 mg.L-1stock solutions provided by Fluka (Madrid, Spain).
Lead
stock standard solutions 1g.L-1 is supplied by Merck (Darmstad,
Germany). Nitric acid 69% is obtained from Merck (Darmstad,
Germany). Hydrogen peroxide 33% was supplied by Fluka
(Madrid, Spain).
Hydrochloric acid 37%
was obtained from (Sigma-Aldrich). Acetone 99.7% was provided Carlo Erba (Milan, Italy) and was used to decontaminate the
samples. Deionized water of 18 MΩ cm-1 resistivity is obtained
by introducing bi-distilled water in Milli-Q water
system (Millipore Corporation, MA, USA).
All plastic and
glassware were soaked overnight in nitric acid to avoid contamination.
Apparatus
Jena Zeenit 700P Analytic model atomic absorption spectrometer
with deuterium background correction, including a transversely heated graphite
atomizer was used. Lead hollow-cathode lamp was used as a radiation source.
Measurement of lead concentrations was performed using an MP60 sampler and pyrolytical graphite platform tubes (Analytik
Jena, part number 407-A85.025).
Parameters for
electro-thermal atomic absorption spectrometer (ET-AAS) are optimized and
validated in all matrices (air, blood, urine and hair).
These parameters are
presented in Table 1.
Samples
collection
Blood samples were
collected in heparinized tubes. Urine
samples were collected in clean bottles. These samples were transported and
conserved in the laboratory at 4°C. Hair samples, with length between 1 and 4
cm, and 0.5 cm
in diameter were cut close to the origin in the occipital area. The samples
were identified and stored at room temperature in plastic bags.
Statistics
Data analysis was
performed using the sixth version of Epi-InfoTM
software IBM SPSS statistics version 21 (Chicago, IL, USA). The validity of the
models for comparison of means was studied using the ANOVA test. Significance
was retained for P value <0.05.
|
Table 1: Operating parameters for Lead analysis using
ET-AAS* |
|
|||
|
Parameters |
|
|||
|
Lamp current (mA) |
4.0 |
|||
|
Air flow rate (mL.min-1) |
5 (stopped during atomizing) |
|||
|
Sample volume (µL) |
20 |
|||
|
Furnace program |
Blood |
Urine |
Hair |
Air |
|
Drying(°C -10 seconds) |
140 |
140 |
120 |
120 |
|
Ashing (°C -10 seconds) |
700 |
500 |
500 |
400 |
|
Atomizing (°C
-10 seconds) |
1500 |
1500 |
1500 |
1500 |
|
Cleaning (°C -10
seconds) |
2000 |
2000 |
2000 |
2000 |
Results
This study concerned 70 male subjects: forty
battery manufacturing factory workers and thirty controls (non-exposed to lead
in their workplaces). Cases
are aged between 22 years and 63 years with a median of 41 years. Controls are
aged between 27 years and 54 years with a median of 36 years (table 2).
Workstations occupied by exposed workers are distributed into seven stations
noted “P”:
P1 : lead pulp preparation operator,
P2 : grid operator,
P3 : lead pulp pasting operator,
P4 : assembler,
P5 : machine operator,
|
Table 2: Age
characteristics of case and control groups |
||||
|
Group |
Age Interval |
Average |
SD* |
Median |
|
Cases |
22 – 63 |
37.6 |
± 6.8 |
41 |
|
Controls |
27 – 54 |
33,5 |
± 4.5 |
36 |
P6 : electrician,
P7 : welder.
After
analyzing biological samples of the studied groups in the different sites, the
results showed important lead exposure among workers. Lead levels among workers
and controls are shown in table 3. The difference between these groups was more
highlighted through the hair matrix, rather than blood and urine samples.
The set of
biological samples, which was taken from workers active in the 7 workstations,
was used to study the correlation between lead levels and environmental
contaminations. The obtained lead values were present in table 4.
|
Table 3: Lead blood, urine and hair concentrations among cases and controls. |
||||||
|
|
Pb-Blood (µg/L) |
Pb-Urine (µg/g creatinine) |
Pb-Hair (µg/g) |
|||
|
|
Case |
Control |
Case |
Control |
Case |
Control |
|
Pb level |
447 – 1389 |
64 - 140 |
120 – 430 |
13 – 38 |
177 – 8367 |
0.28 – 6.2 |
|
Average ±SD* |
804±191.8 |
93.8±25.5 |
330±16.4 |
24±5.9 |
2091±194 |
13±1.5 |
|
Median |
794 |
88.5 |
200 |
24 |
1584 |
1.5 |
|
Table 4: Lead
atmospheric, blood, urine and hair concentrations in the seven workstations. |
||||||||
|
Workstation |
P1 |
P2 |
P3 |
P4 |
P5 |
P6 |
P7 |
Average |
|
Pb(mg/m3) |
0.13 |
0.25 |
0.17 |
1.72 |
0.14 |
0.03 |
0.51 |
0.42 |
|
Pb-Blood(µg/L) |
840 |
786 |
818 |
872 |
850 |
745 |
809 |
817.14 |
|
Pb-Urine (µg/g creatinine) |
200 |
200 |
224 |
235 |
230 |
200 |
280 |
224.14 |
|
Pb-Hair (µg/g) |
2473 |
2126 |
1920 |
2040 |
871 |
1757 |
1380 |
1795.29 |
|
Table 5: Correlation between
biologic matrices among cases and controls R (p<0.05). |
||
|
|
Cases |
Controls |
|
(Pb-Hair) – (Pb-Blood) |
0.017 |
0.67 |
|
(Pb-Hair) – (Pb-Urine) |
-0.21 |
0.60 |
|
(Pb-Blood) –(Pb-Urine) |
0.8 |
0.48 |
|
Table 6: Lead concentrations among cases in function of occupational seniority. |
|||
|
Occupational seniority |
Pb-Blood (µg/L) |
Pb-Urine (µg/g creatinine) |
Pb-Hair (µg/g) |
|
< 2 years |
745.25 |
140 |
1123.5 |
|
2-10 years |
749.47 |
213.84 |
2200.33 |
|
11-20 years |
826.4
|
233 |
2490.7
|
|
> 20 years |
799.5
|
235 |
3335.75
|
The
highest intensity of exposure corresponded to the station P4 where the highest
level of Pb in blood was noted. However, the highest amount
of lead in hair samples was found in the station P1. The correlations between
the different biological associations (hair-blood, hair-urine, and blood-urine)
among cases and controls were present in the table 5.
Lead
levels in worker’s samples were present in terms of seniority, which was
divided in 4 intervals (Table 6).
Discussion
The
maximum-tolerated doses for lead in biological matrices are 400 µg/L in blood
and 25 µg/g creatinine in urine [6,7].
Lead exposure in the studied manufacture employees can be assessed by comparing
Pb values in worker and control groups. The average
of lead concentration in air samples is 0.42 mg/m3 while the maximum allowed
level is 0.2 mg/m3 [10]. This could explain the high lead concentrations in our
studied workers' samples. Blood lead level may reflect both recent and chronic exposures. In
long-term exposures, high lead rates could be related to the mobilization of
stored metal from bone and soft tissues [8-10].The environmental exposure to
lead in Tunisia is relatively lower compared to other countries. The average Pb-Hair of control group was only 2.9µg/g in our series.
This
is still comparable to the rates of other industrialized countries such as
Poland and Italy [11]. Lead levels in biologic matrices are particularly high
in exposed workers. In our study, the workstation highest Pb-Blood
and Pb-Urine concentrations did not match those with
the highest Pb-Hair levels. This could signify that
the exposure-intoxication relationship is multifactorial[12,13].
The
hair lead concentration seems to be higher and more stable in case of long-term
exposures.
The
rates may be influenced by the logistic and human communications between
different workstations [14]. The hair lead concentration is significantly correlated
to the design of the workplace and to the implementation of personal protection
policy.
The
correlation between the lead concentration in biological matrices and its
concentrations in hair may be evident and was verified by several studies[14-16].
The
stability of the hair as matrix and its direct interference with the
environmental sources of exposure may be origin of the fluctuations in the
results of some other studies [17].
The
significant correlation between Pb-hair and Pb-blood suggests the efficiency and effectiveness of using hair for assessing
occupational exposure specially in highly polluted areas [18-20].
The
results of this study contribute one more time to the recommendation of the
reinforcement of personal worker protection and implementation of clear a
safety policy. The aim is to reduce the consequences of intoxication especially
in worker population with several comorbid factors.
Conclusion
This study
highlighted the effectiveness of using of human hair as a biological marker of
occupational chronic lead exposure and its confrontation to the conventional
used matrices (Blood and urine) which are more contributive in acute lead
poisoning. However, the lack knowledge especially regarding hair maximum
concentration limits and the interference of some environmental and personal
factors in the exposure mechanism may limit the usefulness of this matrix. Lead
hair concentration could help in monitoring environmental and occupational
pollution. Moreover, hair provides a memory of past long-term lead exposure.
The hair is
easy to collect and provides stable samples. Its study could contribute
reproducible information useful in the follow-up of exposed population.
Conflict of interest: None
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