الفهرس 
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Abstract
Benzene is one of the most important petroleum product that has many applications in industry, dyes, leather industry, fuel for cars and many other applications necessary for modern life. It has many bio-hazards for workers who work or use this toxic agent.
Researches, scientific and field studies proved the presence of numerous hazards as a result of exposure to benzene in work places or during daily activity. Car drivers represent a category of workers exposed to benzene during daily activity, filling car tanks with fuel and during the existence in car stations.
This work aims to study the changes in some hematological, biophysical and biochemical parameters as a result of exposure to benzene in the blood of car drivers in Alexandria city and nearby regions. The car drivers participated in this study were75 driver divided into subgroups starting from exposure period less than five years to exposure group period larger than twenty years exposure period in addition to 25 control healthy individuals.
Urine and blood samples were collected from all the control and car drivers to carry out the following biochemical and biophysical analysis:
• Red blood cells relative viscosity.
• Red blood cells hemolysis degree.
• Red blood cells aggregation shape parameter (ASP).
• Red blood cells form factor (FF).
• Complete blood counts (CBC), by cell analyzer.
• Malondialdehyde concentration (MDA).
• Total antioxidant.
• Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST).
• Serum creatinine.
Estimation of some mineral elements concentrations, e.g., Aluminium, Cadmium, Copper, Mercury, Lead, Selenium, Zinc and Iron in plasma and red blood cells.
Benzene in ambient air of the different workplaces was measured using Photovac ComboPro 2020, USA, with range limit up to 100 ppm. The obtained levels ranged between0.004 – 0.090 ppm (average 0.0.036±0.015 ppm). The average levels are in general lower than the reported values for short-time exposure level (STEL) of 1 ppm recommended by OSHA in 1988 or 2.5 ppm recommended by the American Conference of Governmental Industrial hygienists (ACGIH).
Trans, t-muconic acid was not found in the blood of controls but present in the urine at a level of 0.19 ±0.08 mg/g creatinine (mean ± SD). The variability of the concentration of t,t-muconic acid in the blood and urine of exposed workers was high. The concentrations in the blood averaged 0.76±0.35 mg/L and in the urine 1.26±0.35 mg/g creatinine.
Phenol, on the other hand, was detectable in all blood and urine samples, with mean concentrations in the urine and blood of exposed workers 92.7% and118.94% above control values respectively.
The average relative viscosity was highest (3.01± 0.20) in the group of workers of working period between 5 to 10 years, where it declined after that to reach a minimum value of 2.24 ± 0.19 in the group of working period of 15 to less than 20 years, followed by slight rising to 2.53±0.16 in the group of workers of more than 20 years working period.
The tendency for hemolysis of RBCs was higher in the blood samples withdrawn from benzene-exposed workers, also, the aggregation shape parameter increased by 40.32 % and the form factor by 22.41 %b(199.81 ±6.86) occurred in the car driver group of 15 to less than 20 years working period.
The data also revealed, also, that some counts were lower than the lower level of the accepted normal range. According to Table 6-10, using chi-square statistics, neutrophils, RBCs, HGB, HCT, MCH, and MCHC showed significant difference.
Low level benzene pollution resulted in increased oxidative stress in exposed workers. The determined parameters were indicative of such condition. The mean malondialdehyde (MDA) level was 78.63 % higher than the corresponding control values. In the meantime, the antioxidant capacity was low averaging 38.96 % less than control.
With respect to the determined trace elements in both the blood of control subjects and car drivers, it is clear that some elements suffered reduction in concentration, i.e., in the plasma of car drivers, Cu, Se, zinc and iron. While the other determined elements were increased, i.e., Al, Cd, Pb, and mercury(Hg).
In the RBCs of the car drivers, the elements concentrations of Al, Cd, and increased while the others elements, namely; Cu, Hg, Pb, Se, Zn , and Fe decreased.
The disturbance in many inorganic elements in the blood of personnel chronically exposed to benzene was quite evident. These elements are essential for a multitude of biological processes and their homeostasis, which is maintained within strict limits, is critical for life. Disruption of such homeostasis may lead to oxidative stress. The generation of free radicals in living systems is closely linked with the participation of redoxactive metals which undergo redox cycling reactions and possess the ability to produce reactive radicals in biological systems.