EL-MINIA MED., BULL., VOL. 19, NO. 2, JUNE, 2008
Hussein et al
THE EFFECT OF BENZENE ON SEMINAL
PARAMETERS AND TESTICULAR FUNCTION
By
Alayman F. Hussein, Mamdouh Abol-Nasr, and *Manal Abd El-Aziz
Departments of Urology and *Forensic Medicine
El-Minia Faculty of Medicine
ABSTRACT:
Objective: To investigate the effect of prolonged exposure to benzene on the
semen parameters and hence male reproductive function among men working at
gas stations and occupationally exposed to these chemical substances.
Participants: Eighty-eight workers at gasoline service stations with a mean age of
33.51±5.72 (Range: 24-52) were included in this study. Participants were exposed
to benzene and related products with a duration of exposure varied from one upto
28 years (mean: 8.57±5.39).
Methods: All participants are subjected to clinical history taking and physical
examination including measuring the size of both testes. Semen analyses were
performed to all participants. In addition, we measured a morning blood sample for
serum testosterone and follicular stimulating hormones. The data were then studied
and analyzed for the correlation between the seminal parameters and hormonal
profile, and the duration of exposure to benzene
Results: The most evident abnormal semen characteristics include reduction in
sperm concentration, motility, normal morphological forms, and the semen
volume. The duration of exposure correlates with the declined quality of seminal
variables. We found that sperm motility and concentration are affected first (after 5
years), then sperm morphology, and seminal volume are affected later (after 7
years).
Conclusion: Occupational exposure to benzene could adversely interfere with the
human reproduction and fertility. The mechanism of these effects is not known.
Further molecular biological studies on the male reproductive organs are required.
KEY WORDS:
Benzene
Male infertility
Semen
Aromatic hydrocarbons
INTRODUCTION:
Benzene is a liquid inflamemable, and volatile organic compound
that is obtained on refinement of the
crude petroleum. This organic substance is one of the aromatic
hydrocarbons. It is made up primarily
from many carbon and hydrogen
atoms. Benzene is added to prevent
engine knocking with a subsequent
exposure through the cars' exhaust
fumes and evaporation from gasoline
service stations. Absorption of benzene
is either by inhalation of contaminated
air or by dermal exposure.1
Polychlorinated aromatic hydrocarbons (PCAHS) have been described
as endocrine disruptors in animals and
in accidentally or occupationally
exposed
humans.
Environmental
exposure to the PCAHS may interfere
with sexual maturation and in the longterm, they have an adverse effect on
the human reproduction.2
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EL-MINIA MED., BULL., VOL. 19, NO. 2, JUNE, 2008
Since forty years, the public in
the western world has become
increasingly concerned and worry
about the toxicity of environmental
pollutants in relation to the fetal
development and human reproduction.
The more recent epidemiologic
evidence of the decreased quality of
human sperm has drawn attention to
effects on the male reproductive
system.3
Hussein et al
sperm concentration, sperm motility
and percentage of abnormal sperm
forms. A morning blood sample was
withdrawn for the measurement of the
follicular stimu-lating hormone (FSH)
level, total serum testosterone level,
and Leutininzing hormone (LH) level
with the immunometeric assay using
commercially available kits and the
automated analyzer.
Continuous variables were
expressed as mean ± standard
deviation. Parameters of semen
analysis were compared to the normal
values established by the WHO*. All
examined variables were correlated to
the duration of exposure to benzene
and to the age of the participants.
Pearson Correlation Coefficient test,
independent sample t test, Fisher’s
exact and Mann–Whitney U tests were
used for comparison of continuous
variables when appropriate, while the
chi-square test was used to compare
categorical variables, with a p value
less than 0.05 considered significant.
A statistics software (SPSS) was used
for statistical analysis.
Participants and Methods
This study was conducted in
one year duration at El-Minia
University in the period from April
2004 to April 2005. A total of 88 men
working at gasoline service stations at
the governorate and occupationally
exposed to benzene are included in
this study. The mean age of the
patients was 33.51±5.72 years (range:
24-54 years) and the mean duration of
exposure to benzene was 8.57±5.39
years (range: 1-28 years). Participants
involved in this study had normal
testes without any varicocele. Any
participant under radiotherapy or
chemotherapy, and those who were
receiving treatment to improve
spermatogenesis were excluded.
RESULTS:
Out of the included 88 workers,
72 patients were married with 24 of
them suffered primary infertility on
their marriage (33.3%). According to
standardization of WHO, abnormal
seminal parameters were detected in 28
out of 88 workers (31.8%). The mean
semen volume in all workers was 2.9
ml, the mean sperm concentration was
40.8±41.8 million/ml, the mean sperm
motility was 33.3±21% and the mean
normal sperm morphology was
41.4±19.8%.
After clinical history taking,
physical examination was done
including the external genitalia where
the size of both testes was measured
by means of the Prader's orchidometer. The longitudinal accesses of
both testes were measured separately,
and mean volume of both testes was
calculated. Semen analysis, according
to standards of The World Health
Organization (WHO), was done with a
report including the semen volume,
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EL-MINIA MED., BULL., VOL. 19, NO. 2, JUNE, 2008
Hussein et al
Table (1): Semen parameters, testicular longitudinal axis, testosterone and FSH serum
levels in Gas Station workers participants
Semen volume
Sperm conc. (million/ml)
Sperm Motility
Normal sperm forms
Right testis longitudinal Axis
Left testis longitudinal Axis
Total testosterone (ng/dl)
FSH (ng/dl)
Minimum
2 ml
0.00
0%
5%
2 cm
2 cm
99
1.0
The mean right and left
testicular longitudinal axis was 4.13
cm and 3.96 cm respectively. The
mean serum levels of testosterone and
FSH was 384.81 ng/dl and 7.73 ng/dl
respectively. All these data are shown
in table (1).
Maximum
4 ml
205.00
75 %
85 %
5.5 cm
5.0 cm
890
11.0
Mean ± Sd
2.8955 ± 0.5856
40.8710 ± 41.8926
33.2791 ± 20.9659
41.4302 ± 19.7987
4.1314 ± 1.0365
3.9667 ± 1.0321
384.81 ± 238.03
7.7333 ± 2.6853
exposure, there is a significant
reduction of sperm concentration,
sperm motility and percentage of
normal sperm forms (p<0.001,
p<0.001 and p=0.013 respectively)
and insignificant reduction of semen
volume (p=0.081). There were
insignificant changes in the testicular
longitudinal axis, serum level of total
testosterone and FSH in correlation to
the duration of exposure to benzene.
All these data are shown in table (2).
The criteria of abnormal semen
parameters are significantly correlated
to the duration of benzene exposure.
With the increase in the duration of
Table (2): Changes in semen parameters in correlation to duration of exposure and
age of Gas Station workers participants
Duration of benzene exposure
Sperm concentration
Sperm motility
Normal sperm forms
Semen volume
Right testis longitudinal axis
Pearson correlation
- 0.446
- 0.412
- 0.267
- 0.187
0.148
P value
0.001**
0.001**
0.013*
0.081
0.337
0.171
0.188
-0.210
Total testosterone
0.199
Folicular Stimulating Hormone
 Significant at the 0. 05 level (2- tailed) –
 ** highly significant at the 0. 01 (2- tailed)
0.374
0.293
Left testis size longitudinal axis
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EL-MINIA MED., BULL., VOL. 19, NO. 2, JUNE, 2008
Using a cut-point of five years
exposure, we found significant
difference in sperm concentration (t=4.845, p<0.001) and sperm motility
(t=-3.371, p=0.001) between workers
with duration of exposure more than 5
years and those with duration of
exposure less than 5 years (Figure
1&2) and insignificant difference in
the percentage of normal sperm forms
(t=-0.85, p=0.398) (Figure 2). With
Hussein et al
more duration of benzene exposure,
(7 years), we found significant
difference in sperm concentration (t=4.864, p<0.001), sperm motility (t=4.619, p<0.001) and percentage of
normal sperm forms (t=-2.419,
p=0.018) between workers with
duration of exposure more than 7
years and those with duration of
exposure less than 7 years (Figure
3&4).
Figure 2: Relation between sperm motility
and normal forms and duration of
exposure
50
80
60
40
20
40
Percentage
Sperm
concetration
Figure 1: Relation between sperm
concentration and duration of exposure
30.75
30
20
10
77.63
29.45
0
46.79
Motility
> 5 years exposure
40.46
44.84
0
< 5 years exposure
> 5 years exposure
Normal forms
< 5 years exposure
Figure 4: Re lation be twe e n spe rn
motility and normal forms and
duration of e xposure
Percentage
Sperm
concetration
Figure 3: Re lation be twe e n spe rn
conce ntration and duration of e xposure
24.11
Motility
> 7 ye ars e xposure
< 7 ye ars e xposure
> 7 ye ars e xposure
323
36.52
Normal forms
< 7 ye ars e xposure
EL-MINIA MED., BULL., VOL. 19, NO. 2, JUNE, 2008
Hussein et al
sperm vitality and motility in the
exposed workers. The mean acrosin
activity, gamma–glutamine transferase
activity and lactate dehydrogenase-C4
relative activity in the exposed workers
were lower, and the fructose
concentration was higher than those in
the control group. There were negative
correlations between sperm vitality,
sperm activity, acrosin activity or
LDH-C4 relative activity and the
working history.8
DISCUSSION:
The
role
of
specific
environmental and occupational factors
in health problems is incompletely
elucidated. Various physical and
chemical occupational agents have
been shown to affect male reproductive
function. Chemicals are proved to
cause genital tract malformations, such
as hypospadias, cryptorchidism, feminization, and altered sexual behavior
and reduced fertility in both men and
women. Occupational exposure to
traffic pollution has been reported to
reduce the semen quality.4
Previous studies have shown that
on exposure to hydrcarbons, the sperm
motion parameters (in the exposure
group) such as linearity (LIN),
straightness (STR), and the sperm
count were decreased significantly, and
the abnormality rate of viscidity,
coagulation and sperm count were
increased significantly as compared
with the control group.9 (Tan et al.,
2002). The reduced semen quality are
coinciding with Xiao et al.(1999) and
Kawaguchi
et
al.,(2004),
who
concluded that occupational exposure
to hydrocarbons can affect the
worker’s semen quality especially the
sperm count and movement ability.10,11
Benzene has toxic effects on
sperms either directly or by inducing
hormonal changes. Testicular failure
secondary to benzene exposure leads to
increased serum level of FSH and may
be associated with reduction of
testicular volume. Indeed, benzene
behaves as an endocrine disruptors.5
Benzene could reduce the sperm
count, motility, and vitality, together
with a reduced forward velocity and
increased the percentage of the
abnormal spermatic forms.6 It is
suggested that all such effects are
caused by androgen deprivation and all
such changes were reversible within
two weeks of withdrawal from further
benzene exposure.6 Results of our
study are consistent with these results.
Animals exposed to benzene
showed
azoospermia
which
is
maintained for 150 days of observation
period. The libido and fertility of the
treated animals were zero. The effects
appear to be mediated through the
testes.12 (Lohiya et al., 1999). In
animal studies with Pathak et al.
(2000), it has been demonstrated that
administration of benzene chromatographic fraction of chloroform extract
of the seeds of Carica papaya have
been done on a dose regimen of 5 and
10 mg/animal/day, orally to male
albino rats, resulted into a total
suppression of cauda epididymal sperm
motility coinciding with a decrease in
sperm count, viability, and an increase
The reduced semen quality as a
result of benzene exposure observed in
this study are in agreement with Wang
et al., 2000, who found that exposure
to low concentration of benzene could
be correlated with the declined quality
of semen in occupational workers.7
The same results also are in
concordance with Xiao et al., 2001,
who suggested that hydrocarbons could
affect the sperm and the function of
accessory gonads leading to decreased
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EL-MINIA MED., BULL., VOL. 19, NO. 2, JUNE, 2008
in percent of abnormal spermatozoa
during 60-150 days observation
period.13
Hussein et al
In relation to the duration of exposure
to benzene, the current results are in
the same line with Xiao et al. (2001),
who suggesting that prolonged exposure to benzene had resulted into a
reduced sperm activity and motility.8
The reduced testicular size,
which could be correlated to the
changes in the serum FSH level, is
consistent with the study of Watanabe
and Qanuki (1999), which demonstrated that diesel engine exhaust
depressed gonadotrophic hormones
and inhibited spermatogenesis in rats.
The same authors reported that the
smaller testes will reduce the sperm
output
in
adults,
and
could
subsequently affect the fertility.14
Conclusion:
This study provides good
epidemiological evidence that occupational exposure to benzene could
influence the male reproductive
function, and it is inversely correlated
to the semen quality with a substantial
role in reducing the human fertility.
Furthermore, the study demonstrates
that the duration of exposure to
benzene plays an important role in
detrimental male reproductive toxicological effects.
The recent results supporting the
hypothesis found by Elly Den et al.
(2002), that there is a negative
correlation between the biomarkers
related to exposure to (PCAHS) and
the sexual maturation. This may be
explained as (PCAHS) behave as an
endocrine disruptors, but their precise
mechanism of action remains under
investigation.2 Polychlorinated biphenyls interact with the receptors of sex
steroid hormones, by which they may
exert estrogenic, androgenic, or antiestrogenic effects.15 (Brouwer et al.,
1995).
Epidemiological
studies
produced evidences suggesting that
environmental and occupational exposure to endocrine disruptors may
explain the decreasing quality and
quantity of human sperm (Swan et al.,
1997),16 the increasing incidence of
testicular cancer (Felming et al.,
1999),17 and cryptorchidism (Weinder
et al., 1998).18
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G. (2002): Reversible anti-fertility
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Sexual maturation in relation to
Polychlorinated Aromatic Hydro-
There is a body of evidences
linking the duration of exposure to
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Z.; Li Y. N.; Wang Q. L., and Ji J. M.
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on the semen quality of occupational
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‫‪EL-MINIA MED., BULL., VOL. 19, NO. 2, JUNE, 2008‬‬
‫األيمن فتحي حسين‪ -‬ممدوح محمد أبو النصر‪ -‬منال عبد العزيز*‬
‫قسم المسالك البولية ‪ -‬قسم الطب الشرعي*‬
‫كلية طب المنيا‬
‫أجريتتتذ تتترا ة لرةيتتتا اريتتتيب ة اتتتتر ة يتتتلقيا ة إلتاجتتتا للتتت ة رتتتلر ة إلجتقيتتتا لرجتتتت‬
‫ة معرضتتيم ميإليتتت لقإلت يم هتتد لمليتتب لةلت م‪ .‬تتتذ ة قإلت يم قتتل ةمتتاملذ ة لرةيتتا للت ‪88‬‬
‫ر ك قعل ةياقعتل ج ل أيا أمرةض لض يا أ اإلتيتليا ذتر ك اتب ةيتاقعتل‬
‫لتمال مم ة رجت‬
‫ة متتللإليم أ ة تتريم ياإلتتت م أع لرتتترةذ قيتتا متتم ةجتت اإلمتتي ة رتتلر ة اإلتيتتليا أ ا‪.‬يتتيم‬
‫ة ظتتت ا ة إلجتقيتتا قتتل اتتب اجميتتت ليإلتتتذ ة يتتت ة مإل ت ع لرةيتتا لتتلل ‪.‬رذيتتا ة ‪.‬ي ةإلتتتذ‬
‫ة مإل يا ذميا ة يتت ة مإلت ع – ذتر ك إليتقا ة ‪.‬ي ةإلتتذ ة مإل يتا ة ممت ا – ذمتت اتب اجميتت‬
‫ليإلتذ ة لب ر ك ريتس ميا ى رم م ة اييا ياير م ذر ك ة يرمت م ة مإلمت للصتيايم‬
‫ة رع ياب ةهرة ق ةي ا ة غل ة إللتميا ذمت ةمتاملذ ة لرةيتا للت قيتيتتذ ‪.‬جتب ة لصتيايم‬
‫ةيتامرذ ة لرةيتا متل‬
‫ق ةي ا جيت ةال رذيل ميار ق‪.‬يث اب قيتس ذت لصتيا للت ‪.‬تل‬
‫يإلا ذتملا‬
‫قل أيفرذ إلات ج رة ة ق‪.‬ث لم أم إلتك ال رة مل‪ .‬ظت هد ة رلر لل ة لصتت‬
‫لإلتتل تتاالر ة رجتتت ةعذاتتر اعرضتتت لقإلت يم هتتد ظيفتتايب لةلت م‪ .‬تتتذ ة قإلت يم‪ -‬ذتتتم تترة‬
‫ة اتتل ر مل‪ .‬ظتتت هتتد إلرتتح لتتلل ‪.‬رذيتتا ة ‪.‬ي ةإلتتتذ ة مإل يتتا ذتتر ك يتتتل لتتلل ة ‪.‬ي ةإلتتتذ‬
‫ة مإل يا ة مم ا‪ -‬ذمت أاقاذ ترا ة لرةيتا أم إلتتك إلرتح هتد ميتا ى رمت م ة اييا يتاير م‬
‫قت لب ذرة صغر هد ‪.‬جب ة لصيايم ذتإلذ را ة اغييرةذ ا لةل ق يتل مل ة اعرض لقإل يم‬
‫متتت يتتتل هاتتر ة اعتترض لقإل ت يم و ت لمتتس يتتإل ةذ ياتتةار هر ت لتتلل ‪.‬رذيتتا ة ‪.‬ي ةإلتتتذ‬
‫ة مإل يا‪ -‬ذم لإلل ة ليتل هار ة اعرض و يقت يإل ةذ هتإله قت ضتها و مت يقق هتإلته إلتتك‬
‫إلرح هد ذميا ة يت ة مإل ع للل ة ‪.‬ي ةإلتذ ة مإل يا ة قيعيا‬
‫مم رة ة ق‪.‬ث إلياللح أم ة عمت هد م‪ .‬تذ ة قإل يم ةذار اعرضتت تإلرح ة رتلر ة إلجتقيتا‬
‫ةعمر ة رع ييا ج ‪.‬متيايب قما ة رق‬
‫‪327‬‬