Abstract:
Chromium is one of the toxic heavy metals, which is extensively discharged from
tanning industry to the environment. Chromium has binding potential to biomolecules
in living systems and cause toxicity to biological life. Leather industry has been
categorized as one of the highly polluting industry. Tanning industry is polluting the
environment at a higher rate with huge amount of harmful material. These pollutants
are also harmful for environment, humans and aquatic organisms.
The aim of the present study was to investigate the effects of chromium on selected
endocrine hormones, oxidative stress, DNA damage, biochemical and haematological
parameters of tannery workers and environmental parameters. Two major cities,
Peshawar and Sheikhupura, were selected for the sampling sites. Samples of effluents,
ground water, soil and vegetables were collected from the neighboring vicinity of
tanning industries. The background area and adjoining villages were considered as
control areas. Seven trace metals (Cr, Cu, Ni, Cd, Pb, Fe, and Zn) were investigated in
tannery effluents, ground water, soil and dietary vegetables (Spinacia oleracea,
Solanum tuberusom and Solanum melongena) samples using Graphite Furnace
Atomic Absorption Spectrophotometer. It was observed that both soil and
groundwater of study area were badly affected by the toxic elements discharged by
tanning industries. The maximum level of Cr in tannery effluents was 350.15 mg/l,
while in the soil sample it approached to 31.13mg/l. The values of chromium, cobalt,
cadmium, lead and iron in the tannery effluents from Sheikhupura and Peshawar were
above the permissible limits set by WHO (World health organization) and FAO (Food
and Agriculture organization). The concentration of chromium, cadmium, nickel and
lead in study area ground water from Sheikhupura and Peshawar exceeded the
standards of NSDWQ/Pak (National standard for drinking water quality). Vegetables
irrigated with tannery effluents showed elevated level of Cr, Zn, Ni and Cd, which
were above the permissible limits of WHO/FO. There was a significant positive
correlation between all the trace metals in three media, tannery effluent, soil and
ground water (p<0.001). The metal to metal association was supported by
dendrograms using cluster analysis.
A total of 240 smoking and nonsmoking individuals were registered in the study,
including 120 chromium exposed tannery workers and 120 controls. The workers
were selected from the tanneries of Sheikhupura and Peshawar, Pakistan. The average
age of exposure group I was 20-35 years, exposure group II was 36-50 years and
controls were 20-50 years. Hormonal parameters in the blood samples were
determined by commercial kit, Chemiluminescent Microparticle Immunoassay
(CMIA). Oxidative stress parameters were measured in the blood samples by
spectrophotometric methods. DNA damage in lymphocytes was measured by comet
assay (single-cell gel electrophoresis). Blood samples were collected from different
age group subjects (chromium exposed tannery workers and controls).
The results revealed that both smoking and nonsmoking exposed groups showed
significantly higher chromium levels in blood and urine than those of unexposed
groups. The levels of testosterone (326.238± 12), (306.636±13.8) and growth
hormones (0.1030±0.03), (0.0734±0.01) were significantly decreased in both age
groups of male tannery workers exposed to chromium.
The level of progesterone (2.416 ± 1.1), estradiol (48.879 ± 40.1), luteinizing (1.9692±
0.82) and growth hormones of female tannery workers (0.7983±0.1) were
significantly decreased while follicle stimulating hormone (9.2857 ± 0.7) was
significantly increased as compared to unexposed population. Thyroid stimulating
hormone, triiodothyronine and tetraiodothyronine hormones were not affected in
tannery workers. The hormones in tannery workers in group II aged (36-50) were
more affected due to long-term Cr exposure as compared to group 1 with short term
chromium exposure and controls.
This was further supported by correlation and regression analyses of the data. Pearson
correlation showed that the levels of sex hormones (testosterone, progesterone,
estradiol and luteinizing hormone) and growth hormone had negative correlation with
blood chromium concentration in tannery workers.
The present study revealed that occupational exposure to Cr (VI) and Cr (III) can lead
to a detectable DNA damage in tannery workers. DNA damage (28.79± 2.154),
(25.41± 7.199) in smoking and nonsmoking tannery workers were significantly higher
than those of unexposed groups. In addition, DNA damage was significantly
associated with concentration of chromium in blood.
Malondialdehyde (MDA) levels (11.00 ± 0.7), (8.77± 2.3) and superoxide dismutase
(SOD) concentrations (75.178± 2.3), (79.52±1.9) of smoking and nonsmoking
exposed groups were significantly higher than those of unexposed groups. While
glutathione (GSH) levels (59.926 ± 1.5), (55.702 ± 2.3) in smoking and nonsmoking
exposed groups were significantly lower when compared with unexposed groups.
Oxidative stress parameters and DNA damage in group II tannery workers aged (36-
50) with long-term Cr exposure were more affected as compared to tannery workers
in group I with short term chromium exposure and controls. This investigation was
further supported by correlation analysis. There was positive correlation between
levels of blood chromium and DNA damage, MDA and SOD levels, while negative
correlation was observed between blood chromium concentration and GSH levels in
tannery workers. The results showed that duration of exposure and smoking has
significant effect on DNA damage and oxidative stress parameters in tannery workers.
The present study also described biochemical and haematological defects in tannery
workers exposed to hexavalent chromium. From the findings, it is evident that white
blood cells (WBC) (8.373±0.7), red blood cells (RBC) (4.12±0.5), haemoglobin (Hb)
(10.02±1.14), mean corpuscular haemoglobin (MCH) (25.91±1.50), and packed cell
volume (PCV) (42.62±2.0) were lower in exposed groups than that of controls.
The values of liver function tests of tannery workers were found to be within the
normal range in both the age groups except alkaline phosphatase (AP) activity
(121.28±8.3), which was significantly increased in exposed groups. All other
biochemical parameters were found to be within the normal range except the albumin
(Alb) levels which was significantly decreased in exposed groups.
The present study found that occupational exposure to chromium can lead to health
hazards including hormonal abnormalities, oxidative stress, DNA damage and
hematological and biochemical defects in tannery workers.